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'NOW'

Available in: DSQL, PSQL, ESQL

Changed in: 2.0

Description

'NOW' is not a variable but a string literal. It is, however, special in the sense that when you CAST() it to a date/time type, you will get the current date and/or time. The fractional part of the time used to be always .0000, giving an effective seconds precision. In Firebird 2.0 the precision is 3 decimals, i.e. milliseconds. 'NOW' is case-insensitive, and the engine ignores leading or trailing spaces when casting.

Type: CHAR(3)

Examples

 select 'Now' from rdb$database
 -- returns 'Now'

 select cast('Now' as date) from rdb$database
 -- returns e.g. 2008-08-13

 select cast('now' as time) from rdb$database
 -- returns e.g. 14:20:19.6170

 select cast('NOW' as timestamp) from rdb$database
 -- returns e.g. 2008-08-13 14:20:19.6170

Shorthand syntax for the last three statements:

 select date 'Now' from rdb$database

 select time 'now' from rdb$database

 select timestamp 'NOW' from rdb$database

Notes:

• When used with CAST(), 'NOW' always returns the actual date/time, even in PSQL modules, where CURRENT_DATE, CURRENT_TIME and CURRENT_TIMESTAMP return the same value throughout the duration of the outermost routine. This makes 'NOW' useful for measuring time intervals in triggers, procedures and executable blocks.
• When used with the shorthand syntax, 'NOW' is evaluated at parse time and the value is frozen for as long as the statement stays prepared – even across multiple executions of the prepared statement! This is something to be aware of.
• Unless you really need progressing values in PSQL, or frozen values during multiple executions, reading CURRENT_DATE, CURRENT_TIME and CURRENT_TIMESTAMP is generally preferable to using 'NOW'. Be aware though that CURRENT_TIME defaults to seconds precision; to get milliseconds precision, use CURRENT_TIME(3).

See also:
The difference between CURRENT_TIMESTAMP and 'NOW'
CURRENT_TIMESTAMP

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