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The date/time functions provide a powerful set of tools
for manipulating various date/time types.
Table 5-6. Date/Time Functions
Function
Returns
Description
Example
abstime(timestamp)
abstime
convert to abstime
abstime(timestamp 'now')
age(timestamp)
interval
preserve months and years
age(timestamp '1957-06-13')
age(timestamp,timestamp)
interval
preserve months and years
age('now', timestamp '1957-06-13')
date_part(text,timestamp)
float8
portion of date
date_part('dow',timestamp 'now')
date_part(text,interval)
float8
portion of time
date_part('hour',interval '4 hrs 3 mins')
date_trunc(text,timestamp)
timestamp
truncate date
date_trunc('month',abstime 'now')
interval(reltime)
interval
convert to interval
interval(reltime '4 hours')
isfinite(timestamp)
bool
a finite time?
isfinite(timestamp 'now')
isfinite(interval)
bool
a finite time?
isfinite(interval '4 hrs')
reltime(interval)
reltime
convert to reltime
reltime(interval '4 hrs')
timestamp(date)
timestamp
convert to timestamp
timestamp(date 'today')
timestamp(date,time)
timestamp
convert to timestamp
timestamp(timestamp '1998-02-24',time '23:07');
to_char(timestamp,text)
text
convert to string
to_char(timestamp '1998-02-24','DD');
For the
date_part and date_trunc
functions, arguments can be
`year', `month',
`day', `hour',
`minute', and `second',
as well as the more specialized quantities
`decade', `century',
`millennium', `millisecond',
and `microsecond'.
date_part allows `dow'
to return day of week, 'week' to return the
ISO-defined week of year, and `epoch' to return
seconds since 1970 (for timestamp)
or 'epoch' to return total elapsed seconds
(for interval).
