FIRST_VALUE returns the evaluation of the from the first row that qualifies for the aggregate. FIRST_VALUE requires the OVER clause, and is considered an analytic function. FIRST_VALUE has a null treatment option defined below.
FIRST_VALUE( < - value-expression> ) <null treatment> OVER < - window-specification>
Null treatment option | Effect |
---|---|
FIRST_VALUE(x) IGNORE NULLS OVER <window-specification > | Returns first non null value of x in <window-specification > |
FIRST_VALUE(x) RESPECT NULLS OVER <window-specification > | Returns first value, including null of x in <window-specification > |
FIRST_VALUE(x) OVER <window-specification > | Returns first value, including null of x in <window-specification > |
See the topic WINDOW clause of the SELECT statement for more details on defining windows.