JOINS, EXISTS or IN which is better? Few questions on SQL

Question

I have few questions on SQL..

1. How to analyze the performance of a query? Any software, inbuilt features of MSSQL server 2005/2008?

2. What shou

Answer 1

1. check the Excution Plan
2. You can optimise your query by:
   • Make a "arguments search" rather than IN
   • Put Index on session_id

    SELECT * FROM enquiry_courses as Courses, enquiries as Enquiries
    WHERE Enquiries.session_id = '4cd3420a16dbd61c6af58f6199ac00f1'   
    AND Courses.enquiry_id = Enquiries.enquiry_id

3.Exists is better for performance.

EDIT: Exists & IN are better than JOIN for performance issues.

EDIT: I re-wrote the query so that it's faster (I put the most restrictive condition first in the WHERE close)