Mysql indexes

[oliveboy81]

May I ask, exactly what is an index and what category (e.g. database or table or column) does it apply to. Also, how do you delete an index once you have made one? Thanks in advance.

[Anon]

Hi,

an index applies to one or more columns in a table.
You can delete an index like this:

ALTER TABLE tablename DROP INDEX indexname;

Vinai

Will Fisher wrote:

May I ask, exactly what is an index and what category (e.g. database or table or column) does it apply to. Also, how do you delete an index once you have made one? Thanks in advance.

[Anon]

Indices allow for faster lookups. As a general rule of thumb, index the columns that you use the most in where clauses of select statements. If you're saying SELECT * FROM foo WHERE bar = 'something' then index bar. Lookups are faster, but the downside is that inserts are slower because it has to do some internal sorting work... Another downside is that it takes up more space.