sql - Determine if column value is null/non-null in MySQL -


i have 2 tables, 1 containing user data, user, , second contains users have tied accounts in twitter, user_twitter. second table not contain correspodning value each user (those have yet connect account twitter, instance), querying using left join:

select distinct `user_twitter`.uid `connected`  `user`  left join (select uid `user_twitter`) `user_twitter` on `user`.uid = `user_twitter`.uid

what i'd return boolean value (true if user_twitter.uid non-null value, false if null). pointers?

select  a.uid `connected`,         (b.uid not null) bool_val    `user`         left join `user_twitter` b             on a.uid = b.uid

will return 0 false , 1 true. if want string value true or false,

select  a.uid `connected`,         case when b.uid not null 'true' else 'false' end bool_val    `user`         left join `user_twitter` b             on a.uid = b.uid

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