Re: DATETIME vs. INT(11)?

[Rick James]

DATETIME takes 8 bytes of storage.
INT takes 4
TIMESTAMP takes 4
DATE takes 3

DATETIME and TIMESTAMP have lots of useful functions.

TIMESTAMP is stored as GMT and TZ-converted on input/output.
DATETIME -- think of it as a snapshot of the clock on the wall (no timezone, daylight savings time, etc)

The diff of two TIMESTAMPs is a true elapsed time.
The diff of two DATETIMEs can be off by an hour due to DST, or more if data comes from multiple timezones.
The diff of two INTs depends on where the INT comes from (localtime, gmttime, etc).

5 = 4 + 1 -- The extra 1 is because it is NULLable, not NOT NULL. This is usually inappropriate for a time field.

"Using index" -- this is because you specified only the fields in a single index. This only rarely happens in real queries.

If you have a real query, let's continue this discussion with it in mind.

Back to your question:
DATETIME -- Obvious what the value represents.
INT -- smaller
TIMESTAMP -- has both advantages, so I lean toward it.