mysql - table column marked as unique, means it's indexed too, right? -

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i'm trying setup mysql table. following:

id (integer, auto increment, primary) username (varchar 32, unique) email (varchar 32, unique)

i don't want allow duplicate usernames or email addresses in table. example, @ startup, i'll test if supplied username or email exist in table - if do, i'll cancel signup.

if mark username , email columns "unique", mean they're indexed? i'd them indexed can already-exists check efficiently possible,

thanks

yes indexed. how database already-exists check efficiently possible.


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