selecting different categories of values from one column using limit i have table question_bank in my database where i store questions and there is one column called complexity. which defines complexity of question (High,Med,Low). for example i entered 30 question in my table ,10 have high complexity ,10 have medium and 10 have low. is there any way so i can show user 15 questions (5 from each category) 
what i want to achieve 

select * from question_bank where complexity=high and complexity=medium and complexity=low limit 5


this query is just for your idea 

thanks in advance
You could do union on three queries, each selecting only 5 records of choosen complexity :

(select * from question_bank where complexity='high' limit 5) 
union 
(select * from question_bank where complexity='medium'limit 5)


....

This way, you "sum" the records of all your queries (union works only if every request fetch the same columns if I'm not wrong).

You have to be careful to put select statement between parenthesis when using limit and union together (thanks to this answer : https://stackoverflow.com/questions/1415328/combining-union-and-limit-operations-in-mysql-query ), if you fail to do so, your limit won't apply to all select statements.