Database Test 6 Computer Subject
Database Test 6 Computer Subject
Question 21
To remove a relation from an SQL database, _____ is used.
DROP TABLE is the correct SQL command to remove a table permanently from the database.
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Question 22
A subquery must be _____?
A subquery must be enclosed in parentheses to be valid inside SQL queries.
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Question 23
Which is true about a 'join'?
A join is conceptually a Cartesian product followed by a selection and projection operation.
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Question 24
An outer join _____?
Outer join is defined by ANSI SQL standard and is also supported by many DBMS products.
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Question 25
Which is true of a "join"?
Joins can be used as alternatives to many subqueries, particularly EXISTS and IN queries.
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Question 26
The following query have not any error. Which should be replaced to get the desired output?
SELECT ID, name, dept name, salary*10
WHERE instructor;
The query should include FROM instructor instead of WHERE instructor to specify the table.
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Question 27
EXISTS and NOT EXISTS?
EXISTS and NOT EXISTS are logical operators returning true or false depending on whether subquery rows exist.
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Question 28
When using INSERT _____?
INSERT allows adding rows individually or multiple rows in bulk using SELECT.
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Question 29
When using DELETE _____?
DELETE allows removal of single rows or multiple rows based on a condition.
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Question 30
This is Employee table.
Which of the following employee_id will be displayed for the given query?
SELECT * FROM employee WHERE employee_id>1007;
| Employee_id | Name | Salary |
|---|---|---|
| 1005 | Asad | 32000 |
| 1011 | Asim | 24000 |
| 1019 | Waqas | 28000 |
The query selects employees with id greater than 1007. Only 1011 and 1019 satisfy this condition.
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