my table is:
name01 category01
name02 category01
name03 category02
name04 category02
name05 category02
name06 category02
name07 category02
..... I would like to count for each category the number of name
the output i woulk like is something like this (by the example above):
category01 2
category02 5
...
thanks to all that would to help me...
SELECT category, COUNT(*) FROM table GROUP BY category
Although count could be a bit slow on very big tables, so if you run a very big service or operate on a lot of data you might consider cache the result or denormalize the table. (However, these techniques assume a really big table)
this is very basic, but using a GROUP BY statement should give the desired result. ie:
SELECT category, COUNT(*) FROM table GROUP BY category
始终使用COUNT(1)加快执行速度
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