Crowdly

To store user credentials and access permissions.

To define the structure, attributes, and relationships of the database objects.

To store backup copies of the database.

Write the full definition of the DDL in SQL

What does the NOT NULL constraint indicate in SQL?

The column must contain a unique value

The column must be indexed

The column can have a NULL value

The column cannot have a NULL value

Is a subquery that contains a reference to a table that also appears in the outer query

A subquery in an SQL SELECT statement is enclosed in:

capital letters

braces -- {...}

braces -- [...]

braces -- (...)

Which of the following is a correlated subquery?

Uses the result of an outer query to determine the processing of an outer query

Uses the result of an inner query to determine the processing of an inner query

Match the SQL subquery type with its description

A subquery that is defined within the WHERE clause of the outer query

A subquery that returns a single column and a single row

A subquery that is evaluated for each row processed by the outer query

A subquery that is evaluated once for the entire outer query

Which of the following statements is true concerning subqueries?

Cannot return the same result as a query that is not a subquery

Does not start with the word SELECT

Involves the use of an inner and outer query

Cannot use the same table as the outer query

Which keyword is used ...

(match the appropriate)

to eliminate duplicate rows in the result of a subquery?

to define an alias for a subquery?

to include the result of a subquery in the SELECT statement of the outer query?

What does the EXISTS operator return if the subquery returns any rows?

False

Null

True

Error

Match the SQL subquery operator with its function

Checks if a subquery returns any rows

Compares a value with the result of a subquery that returns multiple rows

Checks if a subquery returns no rows

Keyword is commonly used to introduce a subquery