Re: SELECT 'NOW()' - OK, SELECT 'CLOCK_TIMESTAMP()' - ERROR

On 14/08/22 15:40, Piotr Gasidło wrote:
> Hello,
>
> I found strange PostgreSQL 9.3 behavior:
>
>> select now()::timestamp, 'now()'::timestamp;
> now | timestamp
> ----------------------------+----------------------------
> 2014-08-22 08:34:00.883268 | 2014-08-22 08:34:00.883268
>
> Second column is now() in single apostrophes.
>
> Now, I tried similar function, clock_timestamp() and get:
>
>> select clock_timestamp()::timestamp, 'clock_timestamp()'::timestamp;
> ERROR: invalid input syntax for type timestamp: "clock_timestamp()"
> LINE 1: select clock_timestamp()::timestamp, 'clock_timestamp()'::ti...
> ^
>
> Why is NOW() so special? Where is it documented?

Here:
http://www.postgresql.org/docs/current/interactive/functions-datetime.html#FUNCTIONS-DATETIME-CURRENT

"All the date/time data types also accept the special literal value 'now' to
specify the current date and time"

and also here:

http://www.postgresql.org/docs/9.3/static/datatype-datetime.html#AEN5861

Regards

Ian Barwick

--
Ian Barwick http://www.2ndQuadrant.com/
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