CREATING TABLES
Once they are created, external tables are accessed with normal SQL statements?
True
I have a table named School_Friends in my schema. You want to build a table in your schema named School_Friends. This is ______________, because ____________________________________.
possible; my schema is separate from yours, and it is okay for us to have like-named tables in our separate schemas.
When creating a new table, which of the following naming rules apply.
Must begin with a letter
Must contain ONLY A - Z, a - z, 0 - 9, _ (underscore), $, and #
Must be between 1 to 30 characters long
It is possible to create a table by using the CREATE TABLE command in conjunction with a subquery. True or False?
True
CREATE TABLE student_table
(id NUMBER(6),
lname VARCHAR(20),
fname VARCHAR(20),
lunch_num NUMBER(4));
Which of the following statements best describes the above SQL statement:
Creates a table named student_table with four columns: id, lname, fname, lunch_num
CREATE TABLE bioclass
(hire_date DATE DEFAULT SYSDATE,
first_name varchar2(15),
last_name varchar2(15));
The above CREATE TABLE statement is acceptable, and will create a Table named bioclass that contains a hire_date, first_name and last_name column. True or False?
True
DCL, which is the acronym for Data Control Language, allows:
A Database Administrator the ability to grant privileges to users.
Given this employee table:
(employee_id NUMBER(10) NOT NULL,
first_name VARCHAR2(25) NOT NULL,
last_name VARCHAR2(30) NOT NULL,
hire_date DATE DEFAULT sysdate)
What will be the result in the hire_date column following this insert statement:
INSERT INTO employees VALUES (10, 'Natacha', 'Hansen', DEFAULT);
Statement will work and the hire_date column will have the value of the date when the statement was run.
Examine this CREATE TABLE statement:
CREATE TABLE emp_load (employee_number CHAR(5), employee_dob CHAR(20), employee_last_name CHAR(20), employee_first_name CHAR(15), employee_middle_name CHAR(15), employee_hire_date DATE)
ORGANIZATION EXTERNAL TYPE ORACLE_LOADER DEFAULT DIRECTORY def_dir1 ACCESS PARAMETERS (RECORDS DELIMITED BY NEWLINE FIELDS (employee_number CHAR(2), employee_dob CHAR(20), employee_last_name CHAR(18), employee_first_name CHAR(11), employee_middle_name CHAR(11), employee_hire_date CHAR(10) date_format DATE mask "mm/dd/yyyy")) LOCATION ('info.dat'));
What kind of table is created here?
An external table with the data stored in a file outside the database.
USING DATA TYPES
INTERVAL DAY TO SECOND stores a period of time in terms of days, hours, minutes, and seconds. True or False?
True
Which of the following are valid Oracle datatypes?
DATE, TIMESTAMP WITH LOCAL TIMEZONE, BLOB
To store large amounts of text you should simply create a series of VARCHAR2 columns in a table. True or False?
False
The BLOB datatype can max hold 128 Terabytes of data. True or False?
True
MODIFYING A TABLE
ALTER TABLE table_name RENAME can be used to:
Rename a table.
A column's data type can always be changed from NUMBER to VARCHAR2 but not from VARCHAR2 to NUMBER, provided the table is empty. True or False?
False
Comments can be added to a table by using the COMMENT ON TABLE statement. The comments being added are enclosed in:
Single quotes ' '
The FLASHBACK TABLE to BEFORE DROP can restore only the table structure, but not its data back to before the table was dropped. True or False?
False
After issuing a SET UNUSED command on a column, another column with the same name can be added using an ALTER TABLE statement. True or False?
True
Which of the following will correctly change the name of the LOCATIONS table to NEW_LOCATIONS?
RENAME LOCATIONS TO NEW_LOCATIONS
You can use the ALTER TABLE statement to:
All of the above
The following code creates a table named student_table with four columns: id, lname, fname, lunch_num
CREATE TABLE student_table (id NUMBER(6), lname VARCHAR(20), fname VARCHAR(20), lunch_num NUMBER(4));
The lunch_num column in the above table has been marked as UNUSED. Which of the following is the best statement you can use if you wish to remove the UNUSED column from the student_table?
ALTER TABLE DROP UNUSED COLUMNS
The FLASHBACK QUERY statement can restore data back to a point in time before the last COMMIT? True or False?
False
To completely get rid of a table, its contents, its structure, AND release the storage space the keyword is:
DROP
When should you use the SET UNUSED command?
You should use it when the system is being heavily used
You can use DROP COLUMN to drop all columns in a table, leaving a table structure with no columns. True or False?
False
The data type of a column can never be changed once it has been created. True or False?
False
When you use ALTER TABLE to add a column, the new column:
Becomes the last column in the table
marți, 26 februarie 2013
PROGRAMMING: Section 7
INSERT STATEMENTS
Insert statements can be combined with subqueries to create more than one row per statement. True or False?
True
Which of the following statements will add a new customer to the customers table in the Global Fast Foods database?
INSERT INTO customers (id, first_name, last_name, address, city, state, zip, phone_number)
VALUES (145, 'Katie', 'Hernandez', '92 Chico Way', 'Los Angeles', 'CA', 98008, 8586667641);
If the employees table have 7 rows how many rows are inserted into the copy_emps table with the following statement:
INSERT INTO copy_emps (employee_id, first_name, last_name, salary, department_id)
SELECT employee_id, first_name, last_name, salary, department_id
FROM employees
7 rows, as there is no WHERE-clause on the subquery.
To return a table summary on the customers table, which of the following is correct?
DESCRIBE customers, or DESC customers
DML is an acronym that stands for:
Data Manipulation Language
When inserting rows into a table all columns must be given values. True or False?
False
When inserting a new row the null keyword can be included in the values list for any null column. True or False?
True
Is it possible to insert more than one row at a time using an INSERT statement with a VALUES clause?
No, you can only create one row at a time when using the VALUES clause.
What is the quickest way to use today's date when you are creating a new row?
Use the SYSDATE function.
UPDATING COLUMN VALUES AND DELETING ROWS
If you are performing an UPDATE statement with a subquery, it MUST be a correlated subquery?
False
To change an existing row in a table, you can use the UPDATE or INSERT statements. True or False?
False
Assuming there are no Foreign Keys on the EMPLOYEES table, if the following subquery returns one row, how many rows will be deleted from the EMPLOYEES table?
DELETE FROM employees
WHERE department_id =
(SELECT department_id
FROM departments
WHERE department_name LIKE '%Public%');
All the rows in the EMPLOYEES table with department_ids matching the department_id returned by the subquery.
Using your knowledge of the employees table, what would be the result of the following statement:
DELETE FROM employees;
All rows in the employees table will be deleted if there are no constraints on the table.
Which of the following statements best describes what will happen to the student table in this SQL statement?
UPDATE students
SET lunch_number = (SELECT lunch_number FROM student WHERE student_id = 17)
WHERE student_id = 19;
The statement updates the student_table by replacing student id 19's lunch number with student id 17's lunch number.
DELETE statements can use correlated subqueries?
True
How many rows will be deleted from the employees table with the following statement?
DELETE FROM employees
WHERE last_name = 'king';
No rows will be deleted, as no employees match the WHERE-clause.
If the subquery returns one row, how many rows will be deleted from the employees table?
DELETE FROM employees
WHERE department_id = (SELECT department_id FROM departments WHERE department_name LIKE '%Public%');
All rows in the employees table which work in the given department will be deleted.
Is the following statement valid, i.e. is it allowed to update rows in one table, based on a subquery from another table?
UPDATE copy_emp
SET department_id = (SELECT department_id FROM employees WHERE employee_id = 100)
WHERE job_id = (SELECT job_id FROM employees WHERE employee_id = 200);
Yes, this is a perfectly valid statement.
DEFAULT VALUES, MERGE, AND MULTI-TABLE INSERTS
The MERGE function combines the:
INSERT and UPDATE commands
A multi-table insert statement can insert into more than one table?
True
In developing the Employees table, you create a column called hire_date. You assign the hire_date column a DATE datatype with a DEFAULT value of 0 (zero). A user can come back later and enter the correct hire_date. This is __________.
A bad idea. The default value must match the DATE datatype of the column.
Which statement below will not insert a row of data onto a table?
INSERT INTO (id, lname, fname, lunch_num)
VALUES (143354, 'Roberts', 'Cameron', 6543);
If a default value was set for a null column, Oracle sets the column to the default value. However, if no default value was set when the column was created, Oracle inserts an empty space. True or False?
False
The MERGE statement can be used to update rows in one table based on values in another table and if the update fails, then the rows will automatically be inserted instead. True or False?
True
A multi-table insert statement must have a subquery at the end of the statement?
True
The DEFAULT keyword can be used in the following statements:
INSERT and UPDATE
Insert statements can be combined with subqueries to create more than one row per statement. True or False?
True
Which of the following statements will add a new customer to the customers table in the Global Fast Foods database?
INSERT INTO customers (id, first_name, last_name, address, city, state, zip, phone_number)
VALUES (145, 'Katie', 'Hernandez', '92 Chico Way', 'Los Angeles', 'CA', 98008, 8586667641);
If the employees table have 7 rows how many rows are inserted into the copy_emps table with the following statement:
INSERT INTO copy_emps (employee_id, first_name, last_name, salary, department_id)
SELECT employee_id, first_name, last_name, salary, department_id
FROM employees
7 rows, as there is no WHERE-clause on the subquery.
To return a table summary on the customers table, which of the following is correct?
DESCRIBE customers, or DESC customers
DML is an acronym that stands for:
Data Manipulation Language
When inserting rows into a table all columns must be given values. True or False?
False
When inserting a new row the null keyword can be included in the values list for any null column. True or False?
True
Is it possible to insert more than one row at a time using an INSERT statement with a VALUES clause?
No, you can only create one row at a time when using the VALUES clause.
What is the quickest way to use today's date when you are creating a new row?
Use the SYSDATE function.
UPDATING COLUMN VALUES AND DELETING ROWS
If you are performing an UPDATE statement with a subquery, it MUST be a correlated subquery?
False
To change an existing row in a table, you can use the UPDATE or INSERT statements. True or False?
False
Assuming there are no Foreign Keys on the EMPLOYEES table, if the following subquery returns one row, how many rows will be deleted from the EMPLOYEES table?
DELETE FROM employees
WHERE department_id =
(SELECT department_id
FROM departments
WHERE department_name LIKE '%Public%');
All the rows in the EMPLOYEES table with department_ids matching the department_id returned by the subquery.
Using your knowledge of the employees table, what would be the result of the following statement:
DELETE FROM employees;
All rows in the employees table will be deleted if there are no constraints on the table.
Which of the following statements best describes what will happen to the student table in this SQL statement?
UPDATE students
SET lunch_number = (SELECT lunch_number FROM student WHERE student_id = 17)
WHERE student_id = 19;
The statement updates the student_table by replacing student id 19's lunch number with student id 17's lunch number.
DELETE statements can use correlated subqueries?
True
How many rows will be deleted from the employees table with the following statement?
DELETE FROM employees
WHERE last_name = 'king';
No rows will be deleted, as no employees match the WHERE-clause.
If the subquery returns one row, how many rows will be deleted from the employees table?
DELETE FROM employees
WHERE department_id = (SELECT department_id FROM departments WHERE department_name LIKE '%Public%');
All rows in the employees table which work in the given department will be deleted.
Is the following statement valid, i.e. is it allowed to update rows in one table, based on a subquery from another table?
UPDATE copy_emp
SET department_id = (SELECT department_id FROM employees WHERE employee_id = 100)
WHERE job_id = (SELECT job_id FROM employees WHERE employee_id = 200);
Yes, this is a perfectly valid statement.
DEFAULT VALUES, MERGE, AND MULTI-TABLE INSERTS
The MERGE function combines the:
INSERT and UPDATE commands
A multi-table insert statement can insert into more than one table?
True
In developing the Employees table, you create a column called hire_date. You assign the hire_date column a DATE datatype with a DEFAULT value of 0 (zero). A user can come back later and enter the correct hire_date. This is __________.
A bad idea. The default value must match the DATE datatype of the column.
Which statement below will not insert a row of data onto a table?
INSERT INTO (id, lname, fname, lunch_num)
VALUES (143354, 'Roberts', 'Cameron', 6543);
If a default value was set for a null column, Oracle sets the column to the default value. However, if no default value was set when the column was created, Oracle inserts an empty space. True or False?
False
The MERGE statement can be used to update rows in one table based on values in another table and if the update fails, then the rows will automatically be inserted instead. True or False?
True
A multi-table insert statement must have a subquery at the end of the statement?
True
The DEFAULT keyword can be used in the following statements:
INSERT and UPDATE
PROGRAMMING: Section 6
FUNDAMENTALS OF SUBQUERIES
What will the following statement return:
SELECT last_name, salary
FROM employees
WHERE (department_id, job_id) = (SELECT department_id, job_id FROM employees WHERE employee_id = 103)
A list of last_names and salaries of employees that works in the same department and has the same job_id as that of employee 103.
What will the following statement return:
SELECT employee_id, last_name
FROM employees
WHERE salary =(SELECT MIN(salary) FROM employees GROUP BY department_id);
Nothing. It is an invalid statement.
Which of the following statements is a true guideline for using subqueries?
The outer and inner queries can reference more than one table. They can get data from different tables.
What will the following statement return:
SELECT last_name, salary
FROM employees
WHERE salary < (SELECT salary FROM employees WHERE employee_id = 103)
A list of last_names and salaries of employees that makes less than employee 103
Examine the following statement:
SELECT last_name, salary
FROM employees
WHERE department_id = (SELECT department_id FROM employees WHERE employee_id = 103) AND job_id = (SELECT job_id FROM employees WHERE employee_id = 103)
Is this a pair-wise or non-pair-wise Subquery?
This is an example of a non-pair-wise subquery.
Subqueries can only be placed in the WHERE clause. True or False?
False
SINGLE ROW SUBQUERIES
If the subquery returns no rows will the outer query return any values?
No, because the subquery will be treated like a null value.
Subqueries are limited to four per SQL transaction. True or False?
False
In a non-correlated subquery, the outer query always executes prior to the inner query's execution. True or False?
False
Single row subqueries may not include this operator:
ALL
The result of this statement will be:
SELECT last_name, job_id, salary, department_id
FROM employees
WHERE job_id =(SELECT job_id FROM employees WHERE employee_id = 141) AND department_id = (SELECT department_id FROM departments WHERE location_id =1500)
Only the employees whose job id matches employee 141 and who work in location 1500
MULTIPLE-ROW SUBQUERIES
In a subquery the ALL operator compares a value to every value returned by the inner query. True or False?
True
The SQL multiple-row subquery extends the capability of the single-row syntax through the use of what three comparison operators?
IN, ANY and ALL
Multiple-row subqueries must have NOT, IN or ANY in the WHERE clause of the inner query. True or False?
False
Group functions, such as HAVING and GROUP BY can be used in multiple-row subqueries. True or False?
True
When a multiple-row subquery uses the NOT IN (<>ALL) operator, if one of the values returned by the inner query is a null value, the entire query returns:
No rows returned
Group functions can be used in subqueries even though they may return many rows. True or False?
True
The salary column of the f_staffs table contains the following values: 4000 5050 6000 11000 23000
Which of the following statements will return the last_name and first_name of those employees who earn more than 5000.
SELECT last_name, first_name
FROM f_staffs
WHERE salary IN (SELECT salary FROM f_staffs WHERE salary > 5000);
There can be more than one subquery returning information to the outer query. True or False?
True
CORRELATED SUBQUERIES
The WITH-clause is a way of creating extra tables in the database? (True or False)
False
Correlated Subqueries must work on the same tables in both the inner and outer query?
False
In a correlated subquery the outer and inner query are joined on one or more columns?
True
Table aliases must be used when you are writing correlated subqueries?
True
What will the following statement return:
SELECT last_name, salary
FROM employees
WHERE (department_id, job_id) = (SELECT department_id, job_id FROM employees WHERE employee_id = 103)
A list of last_names and salaries of employees that works in the same department and has the same job_id as that of employee 103.
What will the following statement return:
SELECT employee_id, last_name
FROM employees
WHERE salary =(SELECT MIN(salary) FROM employees GROUP BY department_id);
Nothing. It is an invalid statement.
Which of the following statements is a true guideline for using subqueries?
The outer and inner queries can reference more than one table. They can get data from different tables.
What will the following statement return:
SELECT last_name, salary
FROM employees
WHERE salary < (SELECT salary FROM employees WHERE employee_id = 103)
A list of last_names and salaries of employees that makes less than employee 103
Examine the following statement:
SELECT last_name, salary
FROM employees
WHERE department_id = (SELECT department_id FROM employees WHERE employee_id = 103) AND job_id = (SELECT job_id FROM employees WHERE employee_id = 103)
Is this a pair-wise or non-pair-wise Subquery?
This is an example of a non-pair-wise subquery.
Subqueries can only be placed in the WHERE clause. True or False?
False
SINGLE ROW SUBQUERIES
If the subquery returns no rows will the outer query return any values?
No, because the subquery will be treated like a null value.
Subqueries are limited to four per SQL transaction. True or False?
False
In a non-correlated subquery, the outer query always executes prior to the inner query's execution. True or False?
False
Single row subqueries may not include this operator:
ALL
The result of this statement will be:
SELECT last_name, job_id, salary, department_id
FROM employees
WHERE job_id =(SELECT job_id FROM employees WHERE employee_id = 141) AND department_id = (SELECT department_id FROM departments WHERE location_id =1500)
Only the employees whose job id matches employee 141 and who work in location 1500
MULTIPLE-ROW SUBQUERIES
In a subquery the ALL operator compares a value to every value returned by the inner query. True or False?
True
The SQL multiple-row subquery extends the capability of the single-row syntax through the use of what three comparison operators?
IN, ANY and ALL
Multiple-row subqueries must have NOT, IN or ANY in the WHERE clause of the inner query. True or False?
False
Group functions, such as HAVING and GROUP BY can be used in multiple-row subqueries. True or False?
True
When a multiple-row subquery uses the NOT IN (<>ALL) operator, if one of the values returned by the inner query is a null value, the entire query returns:
No rows returned
Group functions can be used in subqueries even though they may return many rows. True or False?
True
The salary column of the f_staffs table contains the following values: 4000 5050 6000 11000 23000
Which of the following statements will return the last_name and first_name of those employees who earn more than 5000.
SELECT last_name, first_name
FROM f_staffs
WHERE salary IN (SELECT salary FROM f_staffs WHERE salary > 5000);
There can be more than one subquery returning information to the outer query. True or False?
True
CORRELATED SUBQUERIES
The WITH-clause is a way of creating extra tables in the database? (True or False)
False
Correlated Subqueries must work on the same tables in both the inner and outer query?
False
In a correlated subquery the outer and inner query are joined on one or more columns?
True
Table aliases must be used when you are writing correlated subqueries?
True
PROGRAMMING: Section 5
USING GROUP BY AND HAVING CLAUSES
Is the following statement correct?
SELECT department_id, AVG(salary)
FROM employees;
No, because a GROUP BY department_id clause is needed
Which of the following SQL statements could display the number of people with the same last name:
SELECT last_name, COUNT(last_name)
FROM EMPLOYEES
GROUP BY last_name;
How would you alter the following query to list only employees where there existed more than one per last_name with the same last name:
SELECT last_name, COUNT(employee_id)
FROM EMPLOYEES
GROUP BY last_name;
SELECT last_name, COUNT(last_name)
FROM EMPLOYEES
GROUP BY last_name
HAVING COUNT(last_name) > 1;
Read the following SELECT statement. Choose the column or columns that must be included in the GROUP BY clause.
SELECT COUNT(last_name), grade, gender
FROM STUDENTS
GROUP_BY ?????;
grade, gender
Is the following statement correct:
SELECT first_name, last_name, salary, department_id, COUNT(employee_id)
FROM employees
WHERE department_id = 50
GROUP BY last_name, first_name, department_id;
No, because the statement is missing salary in the GROUP BY clause
USING ROLLUP AND CUBE OPERATIONS, AND GROUPING SETS
Examine the following statement:
SELECT department_id, manager_id, job_id, SUM(salary)
FROM employees
GROUP BY GROUPING SETS(.......);
Select the correct GROUP BY GROUPING SETS clause from the following list:
GROUP BY GROUPING SETS ((department_id, manager_id), (department_id, job_id), (manager_id, job_id))
Examine the following statement:
SELECT department_id, manager_id, job_id, SUM(salary)
FROM employees
GROUP BY ROLLUP(department_id, manager_id)
What extra data will this query generate?
The statement will fail.
Examine the following statement:
SELECT department_id, manager_id, job_id, SUM(salary)
FROM employees
GROUP BY GROUPING SETS((department_id, manager_id), (department_id, job_id))
What data will this query generate?
Sum of salaries for (department_id, job_id) and (department_id, manager_id)
If you want to include subtotals and grand totals for all columns mentioned in a GROUP BY clause you should use which of the following extensions to the GROUP BY clause?
CUBE
USING SET OPERATORS
MINUS will give you rows from the first query not present in the second query? (True or False)
True
INTERSECT will give you the common rows found in both queries? (True or False)
True
Which ones of the following are correct SET operators?
UNION, MINUS
UNION ALL, INTERSECTION
The difference between UNION and UNION ALL is
UNION will remove duplicates, UNION ALL returns all rows from all queries
Is the following statement correct?
SELECT department_id, AVG(salary)
FROM employees;
No, because a GROUP BY department_id clause is needed
Which of the following SQL statements could display the number of people with the same last name:
SELECT last_name, COUNT(last_name)
FROM EMPLOYEES
GROUP BY last_name;
How would you alter the following query to list only employees where there existed more than one per last_name with the same last name:
SELECT last_name, COUNT(employee_id)
FROM EMPLOYEES
GROUP BY last_name;
SELECT last_name, COUNT(last_name)
FROM EMPLOYEES
GROUP BY last_name
HAVING COUNT(last_name) > 1;
Read the following SELECT statement. Choose the column or columns that must be included in the GROUP BY clause.
SELECT COUNT(last_name), grade, gender
FROM STUDENTS
GROUP_BY ?????;
grade, gender
Is the following statement correct:
SELECT first_name, last_name, salary, department_id, COUNT(employee_id)
FROM employees
WHERE department_id = 50
GROUP BY last_name, first_name, department_id;
No, because the statement is missing salary in the GROUP BY clause
USING ROLLUP AND CUBE OPERATIONS, AND GROUPING SETS
Examine the following statement:
SELECT department_id, manager_id, job_id, SUM(salary)
FROM employees
GROUP BY GROUPING SETS(.......);
Select the correct GROUP BY GROUPING SETS clause from the following list:
GROUP BY GROUPING SETS ((department_id, manager_id), (department_id, job_id), (manager_id, job_id))
Examine the following statement:
SELECT department_id, manager_id, job_id, SUM(salary)
FROM employees
GROUP BY ROLLUP(department_id, manager_id)
What extra data will this query generate?
The statement will fail.
Examine the following statement:
SELECT department_id, manager_id, job_id, SUM(salary)
FROM employees
GROUP BY GROUPING SETS((department_id, manager_id), (department_id, job_id))
What data will this query generate?
Sum of salaries for (department_id, job_id) and (department_id, manager_id)
If you want to include subtotals and grand totals for all columns mentioned in a GROUP BY clause you should use which of the following extensions to the GROUP BY clause?
CUBE
USING SET OPERATORS
MINUS will give you rows from the first query not present in the second query? (True or False)
True
INTERSECT will give you the common rows found in both queries? (True or False)
True
Which ones of the following are correct SET operators?
UNION, MINUS
UNION ALL, INTERSECTION
The difference between UNION and UNION ALL is
UNION will remove duplicates, UNION ALL returns all rows from all queries
PROGRAMMING: Section 4
GROUP FUNCTIONS
You can use GROUP functions in all clauses of a SELECT statement. True or False?
False
What two group functions can be used with any datatype?
MIN, MAX
Given the following data in the employees table (employee_id, salary, commission_pct)
DATA: (143, 2600, null
144, 2500, null
149, 10500, .2
174, 11000, .3
176, 8600, .2
178, 7000, .15)
What is the result of the following statement:
SELECT AVG(commission_pct)
FROM employees
WHERE employee_id IN( 143,144,149,174,176,178)
0.2125
The following statement will work because it uses the same column with different GROUP functions:
SELECT AVG(salary), MAX(salary), MIN(salary), SUM(salary)
FROM employees;
True or False?
True
Given the following data in the employees table (employee_id, salary, commission_pct)
DATA: (143, 2600, null
144, 2500, null
149, 10500, .2
174, 11000, .3
176, 8600, .2
178, 7000, .15)
What is the result of the following statement:
SELECT SUM(commission_pct), COUNT(salary)
FROM employees
WHERE employee_id IN( 143,144,149,174,176,178)
SUM = .85 and COUNT = 6
COUNT, DISTINCT, NVL
What would the following SQL statement return?
SELECT COUNT(DISTINCT salary)
FROM employees;
The number of unique salaries in the employees table
To include null values in the calculations of a group function, you must:
Convert the null to a value using the NVL( ) function
What would the following SQL statement return?
SELECT COUNT(first_name)
FROM employees;
The total number of non-null first names in the employees table
Using your existing knowledge of the employees table, would the following two statements produce the same result?
SELECT COUNT(*)
FROM employees;
SELECT COUNT(commission_pct)
FROM employees;
No
Given the following data in the employees table (employee_id, salary, commission_pct)
DATA: (143, 2600, null
144, 2500, null
149, 10500, .2
174, 11000, .3
176, 8600, .2
178, 7000, .15)
What is the result of the following statement:
SELECT SUM(commission_pct), COUNT(commission_pct)
FROM employees
WHERE employee_id IN( 143,144,149,174,176,178)
SUM = .85 and COUNT = 4
You can use GROUP functions in all clauses of a SELECT statement. True or False?
False
What two group functions can be used with any datatype?
MIN, MAX
Given the following data in the employees table (employee_id, salary, commission_pct)
DATA: (143, 2600, null
144, 2500, null
149, 10500, .2
174, 11000, .3
176, 8600, .2
178, 7000, .15)
What is the result of the following statement:
SELECT AVG(commission_pct)
FROM employees
WHERE employee_id IN( 143,144,149,174,176,178)
0.2125
The following statement will work because it uses the same column with different GROUP functions:
SELECT AVG(salary), MAX(salary), MIN(salary), SUM(salary)
FROM employees;
True or False?
True
Given the following data in the employees table (employee_id, salary, commission_pct)
DATA: (143, 2600, null
144, 2500, null
149, 10500, .2
174, 11000, .3
176, 8600, .2
178, 7000, .15)
What is the result of the following statement:
SELECT SUM(commission_pct), COUNT(salary)
FROM employees
WHERE employee_id IN( 143,144,149,174,176,178)
SUM = .85 and COUNT = 6
COUNT, DISTINCT, NVL
What would the following SQL statement return?
SELECT COUNT(DISTINCT salary)
FROM employees;
The number of unique salaries in the employees table
To include null values in the calculations of a group function, you must:
Convert the null to a value using the NVL( ) function
What would the following SQL statement return?
SELECT COUNT(first_name)
FROM employees;
The total number of non-null first names in the employees table
Using your existing knowledge of the employees table, would the following two statements produce the same result?
SELECT COUNT(*)
FROM employees;
SELECT COUNT(commission_pct)
FROM employees;
No
Given the following data in the employees table (employee_id, salary, commission_pct)
DATA: (143, 2600, null
144, 2500, null
149, 10500, .2
174, 11000, .3
176, 8600, .2
178, 7000, .15)
What is the result of the following statement:
SELECT SUM(commission_pct), COUNT(commission_pct)
FROM employees
WHERE employee_id IN( 143,144,149,174,176,178)
SUM = .85 and COUNT = 4
PROGRAMMING: Section 3
CROSS JOINS AND NATURAL JOINS
A NATURAL JOIN is based on:
Columns with the same name and datatype
The ___________ join is the ANSI-standard syntax used to generate a Cartesian product.
CROSS
The join column must be included in the select statement when you use the NATURAL JOIN clause. True or False?
False
What happens when you create a Cartesian product?
All rows from one table are joined to all rows of another table
JOIN CLAUSES
The following is a valid SQL statement.
SELECT e.employee_id, e.last_name, d.location_id, department_id
FROM employees e JOIN departments d
USING (department_id) ;
True or False?
True
The primary advantage of using JOIN ON is:
It permits columns with different names to be joined
Table aliases MUST be used with columns referenced in the JOIN USING clause. True or False?
False
You can do nonequi-joins with ANSI-Syntax. True or False?
True
The keywords JOIN _____________ should be used to join tables with the same column names but different datatypes.
USING
INNER VERSUS OUTER JOINS
What is another name for a simple join or an inner join?
Equijoin
Given the following descriptions of the employees and jobs tables, which of the following scripts will display each employee's possible minimum and maximum salaries based on their job title?
EMPLOYEES Table:
Name Null? Type
EMPLOYEE_ID NOT NULL NUMBER (6)
FIRST_NAME VARCHAR2 (20)
LAST_NAME NOT NULL VARCHAR2 (25)
EMAIL NOT NULL VARCHAR2 (25)
PHONE_NUMBER VARCHAR2 (20)
HIRE_DATE NOT NULL DATE
JOB_ID NOT NULL VARCHAR2 (10)
SALARY NUMBER (8,2)
COMMISSION_PCT NUMBER (2,2)
MANAGER_ID NUMBER (6)
DEPARTMENT_ID NUMBER (4)
JOBS Table:
Name Null? Type
JOB_ID NOT NULL VARCHAR2 (10)
JOB_TITLE NOT NULL VARCHAR2 (35)
MIN_SALARY NUMBER (6)
MAX_SALARY NUMBER (6)
SELECT first_name, last_name, job_id, min_salary, max_salary
FROM employees
NATURAL JOIN jobs;
The following statement is an example of what kind of join?
SELECT car.vehicle_id, driver.name
FROM car
LEFT OUTER JOIN driver ON (driver_id) ;
Outer Join
Which syntax would be used to retrieve all rows in both the EMPLOYEES and DEPARTMENTS tables, even when there is no match?
FULL OUTER JOIN
For which of the following tables will all the values be retrieved even if there is no match in the other?
SELECT e.last_name, e.department_id, d.department_name
FROM employees e
LEFT OUTER JOIN departments d
ON (e.department_id = d.department_id);
employees
EMPLOYEES Table:
Name Null? Type
EMPLOYEE_ID NOT NULL NUMBER(6)
FIRST_NAME VARCHAR2(20)
LAST_NAME NOT NULL VARCHAR2(25)
DEPARTMENT_ID NUMBER (4)
DEPARTMENTS Table:
Name Null? Type
DEPARTMENT_ID NOT NULL NUMBER 4
DEPARTMENT_NAME NOT NULL VARCHAR2(30)
MANAGER_ID NUMBER (6)
A query is needed to display each department and its manager name from the above tables. However, not all departments have a manager but we want departments returned in all cases. Which of the following SQL: 1999 syntax scripts will accomplish the task?
SELECT d.department_id, e.first_name, e.last_name
FROM employees e
RIGHT OUTER JOIN departments d
ON (e.employee_id = d.manager_id);
If you select rows from two tables (employees and departments) using an outer join, what will you get? Use the code below to arrive at your answer:
SELECT e.last_name, e.department_id, d.department_name
FROM employees e
LEFT OUTER JOIN departments d
ON (e.department_id = d.department_id);
All employees including those that do not have a departement_id assigned to them
SELF JOINS VERSUS OUTER JOINS
Which of the following database design concepts is implemented with a self join?
Recursive Relationship
Hierarchical queries can walk both Top-Down and Bottom-Up. True or False?
True
Which select statement will return the last name and hire date of an employee and his/ her manager for employees that started in the company before their managers?
SELECT w.last_name, w.hire_date, m.last_name, m.hire_date
FROM employees w , employees m
WHERE w.manager_id = m.employee_id
AND w.hire_date < m.hire_date
Hierarchical queries MUST use the LEVEL pseudo column. True or False?
False
Which SELECT statement implements a self join?
SELECT e.employee_id, m.manager_id
FROM employees e, employees m
WHERE m.employee_id = e.manager_id;
Which of the following database design concepts do you need in your tables to write Hierarchical queries?
Recursive Relationship
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A NATURAL JOIN is based on:
Columns with the same name and datatype
The ___________ join is the ANSI-standard syntax used to generate a Cartesian product.
CROSS
The join column must be included in the select statement when you use the NATURAL JOIN clause. True or False?
False
What happens when you create a Cartesian product?
All rows from one table are joined to all rows of another table
JOIN CLAUSES
The following is a valid SQL statement.
SELECT e.employee_id, e.last_name, d.location_id, department_id
FROM employees e JOIN departments d
USING (department_id) ;
True or False?
True
The primary advantage of using JOIN ON is:
It permits columns with different names to be joined
Table aliases MUST be used with columns referenced in the JOIN USING clause. True or False?
False
You can do nonequi-joins with ANSI-Syntax. True or False?
True
The keywords JOIN _____________ should be used to join tables with the same column names but different datatypes.
USING
INNER VERSUS OUTER JOINS
What is another name for a simple join or an inner join?
Equijoin
Given the following descriptions of the employees and jobs tables, which of the following scripts will display each employee's possible minimum and maximum salaries based on their job title?
EMPLOYEES Table:
Name Null? Type
EMPLOYEE_ID NOT NULL NUMBER (6)
FIRST_NAME VARCHAR2 (20)
LAST_NAME NOT NULL VARCHAR2 (25)
EMAIL NOT NULL VARCHAR2 (25)
PHONE_NUMBER VARCHAR2 (20)
HIRE_DATE NOT NULL DATE
JOB_ID NOT NULL VARCHAR2 (10)
SALARY NUMBER (8,2)
COMMISSION_PCT NUMBER (2,2)
MANAGER_ID NUMBER (6)
DEPARTMENT_ID NUMBER (4)
JOBS Table:
Name Null? Type
JOB_ID NOT NULL VARCHAR2 (10)
JOB_TITLE NOT NULL VARCHAR2 (35)
MIN_SALARY NUMBER (6)
MAX_SALARY NUMBER (6)
SELECT first_name, last_name, job_id, min_salary, max_salary
FROM employees
NATURAL JOIN jobs;
The following statement is an example of what kind of join?
SELECT car.vehicle_id, driver.name
FROM car
LEFT OUTER JOIN driver ON (driver_id) ;
Outer Join
Which syntax would be used to retrieve all rows in both the EMPLOYEES and DEPARTMENTS tables, even when there is no match?
FULL OUTER JOIN
For which of the following tables will all the values be retrieved even if there is no match in the other?
SELECT e.last_name, e.department_id, d.department_name
FROM employees e
LEFT OUTER JOIN departments d
ON (e.department_id = d.department_id);
employees
EMPLOYEES Table:
Name Null? Type
EMPLOYEE_ID NOT NULL NUMBER(6)
FIRST_NAME VARCHAR2(20)
LAST_NAME NOT NULL VARCHAR2(25)
DEPARTMENT_ID NUMBER (4)
DEPARTMENTS Table:
Name Null? Type
DEPARTMENT_ID NOT NULL NUMBER 4
DEPARTMENT_NAME NOT NULL VARCHAR2(30)
MANAGER_ID NUMBER (6)
A query is needed to display each department and its manager name from the above tables. However, not all departments have a manager but we want departments returned in all cases. Which of the following SQL: 1999 syntax scripts will accomplish the task?
SELECT d.department_id, e.first_name, e.last_name
FROM employees e
RIGHT OUTER JOIN departments d
ON (e.employee_id = d.manager_id);
If you select rows from two tables (employees and departments) using an outer join, what will you get? Use the code below to arrive at your answer:
SELECT e.last_name, e.department_id, d.department_name
FROM employees e
LEFT OUTER JOIN departments d
ON (e.department_id = d.department_id);
All employees including those that do not have a departement_id assigned to them
SELF JOINS VERSUS OUTER JOINS
Which of the following database design concepts is implemented with a self join?
Recursive Relationship
Hierarchical queries can walk both Top-Down and Bottom-Up. True or False?
True
Which select statement will return the last name and hire date of an employee and his/ her manager for employees that started in the company before their managers?
SELECT w.last_name, w.hire_date, m.last_name, m.hire_date
FROM employees w , employees m
WHERE w.manager_id = m.employee_id
AND w.hire_date < m.hire_date
Hierarchical queries MUST use the LEVEL pseudo column. True or False?
False
Which SELECT statement implements a self join?
SELECT e.employee_id, m.manager_id
FROM employees e, employees m
WHERE m.employee_id = e.manager_id;
Which of the following database design concepts do you need in your tables to write Hierarchical queries?
Recursive Relationship
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PROGRAMMING: Section 2
CONVERSION FUNCTIONS
You need to display the HIRE_DATE values in this format: 25th of July 2002. Which SELECT statement would you use?
SELECT TO_CHAR(hire_date, 'ddth "of" Month YYYY')
FROM employees;
Which statement is true about SQL functions?
a, b and c are true.
A table has the following definition:
EMPLOYEES(
EMPLOYEE_ID NUMBER(6) NOT NULL,
NAME VARCHAR2(10) NOT NULL,
MANAGER_ID VARCHAR2(6))
and contains the following rows:
(1001, 'Bob Bevan', '200')
(200, 'Natacha Hansen', null)
Will the following query work?
SELECT *
FROM employees
WHERE employee_id = manager_id;
Yes, Oracle will perform implicit datatype conversion.
Which statement will return the salary of e.g. 6000 from the Employees table in the following format $6000.00?
SELECT TO_CHAR(salary, '$99999.00') SALARY
FROM employees
The following script will run successfully. True or False?
SELECT TO_CHAR(TO_DATE("25-DEC-04" ,'dd-MON-yy'))
FROM dual
False
Sysdate is 12-MAY-2004.
You need to store the following date: 7-DEC-89
Which statement about the date format for this value is true?
The RR date format will interpret the year as 1989, and the YY date format will interpret the year as 2089
NULL FUNCTIONS
The following statement returns 0 (zero). True or False?
SELECT 121/NULL
FROM dual;
False
Which function compares two expressions?
NULLIF
If quantity is a number datatype, what is the result of this statement?
SELECT NVL(200/quantity, 'zero') FROM inventory;
The statement fails
With the following data in Employees (last_name, commission_pct, manager_id) what is the result of the following statement?
DATA:
King,null,null
Kochhar, null,100
Vargas, null, 124
Zlotkey,.2, 100
SELECT last_name, NVL2(commission_pct, manager_id, -1) comm
FROM employees ;
King, -1
Kochhar, -1
Vargas, -1
Zlotkey, 100
Consider the following data in Employees table: (last_name, commission_pct, manager_id)
DATA:
King,null,null
Kochhar, null,100
Vargas, null, 124
Zlotkey,.2, 100
What is the result of the following statement:
SELECT last_name, COALESCE(commission_pct, manager_id, -1) comm
FROM employees ;
King, -1
Kochhar, 100
Vargas, 124
Zlotkey, .2
CONDITIONAL EXPRESSIONS
CASE and DECODE evaluate expressions in a similar way to IF-THEN-ELSE logic. However, DECODE is specific to Oracle syntax. True or False?
True
Which statement will return a listing of last names, salaries and a rating of 'Low', 'Medium', 'Good' or 'Excellent' depending on the salary value?
SELECT last_name,salary,
(CASE WHEN salary<5000 THEN 'Low'
WHEN salary<10000 THEN 'Medium'
WHEN salary<20000 THEN 'Good'
ELSE 'Excellent'
END) qualified_salary
FROM employees;
For the given data from Employees (last_name, manager_id) what is the result of the following statement:
DATA:( King, null
Kochhar, 100
De Haan, 100
Hunold, 102
Ernst, 103)
SELECT last_name,
DECODE(manager_id, 100, 'King', 'A N Other') "Works For?"
FROM employees
King, A N Other
Kochhar, King
De Haan, King
Hunold, A N Other
Ernst, A N Other
Which of the following is a conditional expression used in SQL?
CASE
You need to display the HIRE_DATE values in this format: 25th of July 2002. Which SELECT statement would you use?
SELECT TO_CHAR(hire_date, 'ddth "of" Month YYYY')
FROM employees;
Which statement is true about SQL functions?
a, b and c are true.
A table has the following definition:
EMPLOYEES(
EMPLOYEE_ID NUMBER(6) NOT NULL,
NAME VARCHAR2(10) NOT NULL,
MANAGER_ID VARCHAR2(6))
and contains the following rows:
(1001, 'Bob Bevan', '200')
(200, 'Natacha Hansen', null)
Will the following query work?
SELECT *
FROM employees
WHERE employee_id = manager_id;
Yes, Oracle will perform implicit datatype conversion.
Which statement will return the salary of e.g. 6000 from the Employees table in the following format $6000.00?
SELECT TO_CHAR(salary, '$99999.00') SALARY
FROM employees
The following script will run successfully. True or False?
SELECT TO_CHAR(TO_DATE("25-DEC-04" ,'dd-MON-yy'))
FROM dual
False
Sysdate is 12-MAY-2004.
You need to store the following date: 7-DEC-89
Which statement about the date format for this value is true?
The RR date format will interpret the year as 1989, and the YY date format will interpret the year as 2089
NULL FUNCTIONS
The following statement returns 0 (zero). True or False?
SELECT 121/NULL
FROM dual;
False
Which function compares two expressions?
NULLIF
If quantity is a number datatype, what is the result of this statement?
SELECT NVL(200/quantity, 'zero') FROM inventory;
The statement fails
With the following data in Employees (last_name, commission_pct, manager_id) what is the result of the following statement?
DATA:
King,null,null
Kochhar, null,100
Vargas, null, 124
Zlotkey,.2, 100
SELECT last_name, NVL2(commission_pct, manager_id, -1) comm
FROM employees ;
King, -1
Kochhar, -1
Vargas, -1
Zlotkey, 100
Consider the following data in Employees table: (last_name, commission_pct, manager_id)
DATA:
King,null,null
Kochhar, null,100
Vargas, null, 124
Zlotkey,.2, 100
What is the result of the following statement:
SELECT last_name, COALESCE(commission_pct, manager_id, -1) comm
FROM employees ;
King, -1
Kochhar, 100
Vargas, 124
Zlotkey, .2
CONDITIONAL EXPRESSIONS
CASE and DECODE evaluate expressions in a similar way to IF-THEN-ELSE logic. However, DECODE is specific to Oracle syntax. True or False?
True
Which statement will return a listing of last names, salaries and a rating of 'Low', 'Medium', 'Good' or 'Excellent' depending on the salary value?
SELECT last_name,salary,
(CASE WHEN salary<5000 THEN 'Low'
WHEN salary<10000 THEN 'Medium'
WHEN salary<20000 THEN 'Good'
ELSE 'Excellent'
END) qualified_salary
FROM employees;
For the given data from Employees (last_name, manager_id) what is the result of the following statement:
DATA:( King, null
Kochhar, 100
De Haan, 100
Hunold, 102
Ernst, 103)
SELECT last_name,
DECODE(manager_id, 100, 'King', 'A N Other') "Works For?"
FROM employees
King, A N Other
Kochhar, King
De Haan, King
Hunold, A N Other
Ernst, A N Other
Which of the following is a conditional expression used in SQL?
CASE
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