Oracle-转换日期时间格式

Question

I have a temp table.

It has last_update column in 2/10/2018 6:01:50 PM datetime format.

How can I write THE BEST QUERY to display all information that's updated on 02-Oct-2018 day ?

Answer 1

You can use trunc function

select *
  from tab
 where trunc(last_update) = date'2018-10-02'

Answer 2

Use trunc function for getting the same day:

trunc(last_update) = trunc(to_date('02-Oct-2018', 'DD-MONTH-YYYY'))

The TRUNC (date) function returns date with the time portion of the day truncated to the unit specified by the format model fmt. The value returned is always of datatype DATE, even if you specify a different datetime datatype for date. If you omit fmt, then date is truncated to the nearest day .

You can also use format DD-MON-YYYY

Answer 3

It is preferable to avoid TRUNC especially if you have an index on the column last_update . A simple where condition should be better and may be better performant.

WHERE last_update >= date '2018-10-02' AND
      last_update <  date '2018-10-02' + 1