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i have a table that stores about 50k rows and here’s my query :
select * from video where status = 1 and filter = 1 and category = 4
these columns are tinyint and i wonder should i do index on these columns ?
No!
You should always consider index selectivity! If the result of a where clause on an index will return more than 20% of the table, then the index is NOT used, but it’s mantained.
So, for example, the status of your video will be 1, 2, 3, then you have 3 posible states. If those indexes are well distributed we can think that will be 33.3% of them aprox. Then, the query:
will NOT use that index! Instead, a FULL TABLE SCAN would be used.
Please, read about it. It’s really important and a common mistake.
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