MySQL执行查询的时间很长

Question

I have get the query in this thread Sum Multiple Row Date Difference Mysql

The problem now is that the query execution time is so long. I try with a little row data http://sqlfiddle.com/#!2/0d496/1/0 . And it is like crazy thing when i try to execute this query in my local database (my table total row is about 200.000 row), because there is no result even when I wait in a very long time.

I want to ask, is this query by default need a long time to execute? Is it possible to make it faster? How? Thank you.

Answer 1

Try adding Speed to your index:

KEY LogCarIdx ( LogDate , CarId , Speed )

Then the c1 based query uses the index (so says explain). Can't tell the speed difference in the sqlfiddle, but might help in the full size query.