FIRST_VALUE()

First value of the current partition

Result type

The same as type as expr

Syntax

FIRST_VALUE ( <expr> ) OVER <window_name_or_spec>

Table 1. Arguments of `FIRST_VALUE`
Argument	Description
expr	Expression.May contain a table column, constant, variable, expression, scalar function.Aggregate functions are not allowed as an expression.

Value from row in the current partition with a given offset before the current row

Result type

The same as type as expr

Syntax

LAG ( <expr> [, <offset [, <default>]])
  OVER <window_name_or_spec>

Table 1. Arguments of `LAG`
Argument	Description
expr	Expression.May contain a table column, constant, variable, expression, scalar function.Aggregate functions are not allowed as an expression.
offset	The offset in rows before the current row to get the value identified by expr.If offset is not specified, the default is `1`.offset can be a column, subquery or other expression that results in a positive integer value, or another type that can be implicitly converted to `BIGINT`.`offset` cannot be negative (use `LEAD` instead).
default	The default value to return if offset points outside the partition.Default is `NULL`.

The LAG function provides access to the row in the current partition with a given offset before the current row.

If offset points outside the current partition, default will be returned, or NULL if no default was specified.