Hi, Can some one explain me how to optimise this query?

select disticnt(csuser.id), csuser.loginName,csuser.displayName,loginSession.l astlogindatetime,loginSession.activesessions,usert ypes.csusertypeid from User csuser join userroleassign csuserroleassign on csuserroleassign.roleid=52 left outer join userloginsession csloginSession on csloginSession.userid=csuser.id left outer join userusertypeassign usertypes on usertypes.userid=csuser.id limit 15;

If I don't add that distcint keyword, query is returning results in 18 milli seconds; but if I add distcinct it did not return results in two miunutes and finally I have to stop the exection of the query.

Interestingly, if I say select distinct(user.id) from user; then it is pretty quick and returning in 15 milliseconds.

Sorry for asking such a basic question but I'm not that good at SQL.

Thanks and Regards,
Samba