IBM Certification SQL Database 3

Question 1

What is the function of a CHECK constraint in SQL?

Accepted Answer

Validates that column values satisfy a specified condition

Answer

A CHECK constraint enforces a Boolean condition on column values, rejecting any row that does not satisfy it.

Question 2

In IBM Db2, which statement is used to permanently save changes made in a transaction?

Accepted Answer

COMMIT

Answer

COMMIT permanently saves all changes made since the last COMMIT or ROLLBACK point in the current transaction.

Question 3

Which SQL clause filters groups produced by GROUP BY before they are returned?

Accepted Answer

HAVING

Answer

HAVING filters aggregated groups after GROUP BY has been applied, whereas WHERE filters individual rows before grouping.

Question 4

What does the SQL UNION operator do?

Accepted Answer

Combines the result sets of two SELECT statements, removing duplicates

Answer

UNION combines result sets from two SELECT statements and removes duplicate rows; use UNION ALL to keep duplicates.

Question 5

In SQL, what is a surrogate key?

Accepted Answer

A system-generated artificial identifier with no business meaning

Answer

A surrogate key is an artificially generated value (such as an auto-incremented integer) used as a primary key independent of business attributes.

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