sql - Comparing results with today's date?

Question

Is there a way to use the Now() function in SQL to select values with today's date?

I was under the impression Now() would contain the time as well as date, but today's date would have the time set to 00:00:00 and therefore this would never match?

Answer 1

OK, lets do this properly. Select dates matching today, using indexes if available, with all the different date/time types present.

The principle here is the same in each case. We grab rows where the date column is on or after the most recent midnight (today's date with time 00:00:00), and before the next midnight (tomorrow's date with time 00:00:00, but excluding anything with that exact value).

For pure date types, we can do a simple comparison with today's date.

To keep things nice and fast, we're explicitly avoiding doing any manipulation on the dates stored in the DB (the LHS of the where clause in all the examples below). This would potentially trigger a full table scan as the date would have to be computed for every comparison. (This behaviour appears to vary by DBMS, YMMV).

MS SQL Server: (SQL Fiddle | db<>fiddle)

First, using DATE

select * from dates 
where dte = CAST(CURRENT_TIMESTAMP AS DATE)
;

Now with DATETIME:

select * from datetimes 
where dtm >= CAST(CURRENT_TIMESTAMP AS DATE)
and dtm < DATEADD(DD, 1, CAST(CURRENT_TIMESTAMP AS DATE))
;

Lastly with DATETIME2:

select * from datetimes2
where dtm2 >= CAST(CURRENT_TIMESTAMP AS DATE)
and dtm2 < DATEADD(DD, 1, CAST(CURRENT_TIMESTAMP AS DATE))
;

---

MySQL: (SQL Fiddle | db<>fiddle)

Using DATE:

select * from dates 
where dte = cast(now() as date)
;

Using DATETIME:

select * from datetimes 
where dtm >= cast((now()) as date)
and dtm < cast((now() + interval 1 day) as date)
;

---

PostgreSQL: (SQL Fiddle | db<>fiddle)

Using DATE:

select * from dates 
where dte = current_date
;

Using TIMESTAMP WITHOUT TIME ZONE:

select * from timestamps
where ts >= 'today'
and ts < 'tomorrow'
;

---

Oracle: (SQL Fiddle)

Using DATE:

select to_char(dte, 'YYYY-MM-DD HH24:MI:SS') dte
from dates 
where dte >= trunc(current_date)
and dte < trunc(current_date) + 1
;

Using TIMESTAMP:

select to_char(ts, 'YYYY-MM-DD HH24:MI:SS') ts
from timestamps
where ts >= trunc(current_date)
and ts < trunc(current_date) + 1
;

---

SQLite: (SQL Fiddle)

Using date strings:

select * from dates 
where dte = (select date('now'))
;

Using date and time strings:

select dtm from datetimes
where dtm >= datetime(date('now'))
and dtm < datetime(date('now', '+1 day'))
;

Using unix timestamps:

select datetime(dtm, 'unixepoch', 'localtime') from datetimes
where dtm >= strftime('%s', date('now'))
and dtm < strftime('%s', date('now', '+1 day'))
;

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Backup of SQL Fiddle code