first aggregate function

Returns the first value of expr for a group of rows.

Syntax 

first(expr[, ignoreNull) [ FILTER ( WHERE cond ) ] [ IGNORE NULLS | RESPECT NULLS ]

Arguments

  • expr: An expression of any type.

  • ignoreNull: An optional BOOLEAN literal defaulting to false. The default for ignoreNull is false.

  • cond: An optional boolean expression filtering the rows used for aggregation.

  • IGNORE NULLS or RESPECT NULLS: When IGNORE NULLS is used or ignoreNull is true any expr value that is NULL is ignored. The default is RESPECT NULLS.

Returns

The result has the same type as expr.

first is a synonym for first_value aggregate function.

This function is non-deterministic.

Examples 

> SELECT first(col) FROM VALUES (10), (5), (20) AS tab(col);
 10
> SELECT first(col) FROM VALUES (NULL), (5), (20) AS tab(col);
 NULL
> SELECT first(col) IGNORE NULLS FROM VALUES (NULL), (5), (20) AS tab(col);
 5