问题
What is the best way to index a datetime in MySQL? Which method is faster:
- Store the datetime as a double (via unix timestamp)
- Store the datetime as a datetime
The application generating the timestamp data can output either format. Unfortunately, datetime will be a key for this particular data structure so speed will matter.
Also, is it possible to make an index on an expression? For example, index on UNIX_TIMESTAMP(mydate) where mydate is a field in a table and UNIX_TIMESTAMP is a mysql function. I know that Postgres can do it. I'm thinking there must be a way in mysql as well.
回答1:
I don't think either method will be much faster than the other, but if you choose a 'datetime' it will be a lot easier to operate with the standard date time functions.
MySQL doesn't support functional indexes.
回答2:
I think using an integer will be faster because where datetime >= '2010-09-30 01:31:41' will never hit an index. However where intTimestamp >= 237492347 will.
来源：https://stackoverflow.com/questions/2812843/indexing-datetime-in-mysql