After created the index for WHERE clause "WHERE dealer_id = 270001"..It is performing better.I have more dealer ids Should I do it for each dealer_id?
All you've really done is confuse the issue. Please read the wiki page on how to submit performance questions and actually follow the directions. Show us the table structure when the query is performing poorly ALONG WITH explain analyze output, so we can see how the query is being handled by the db. Adding indexes for just one particular value isn't likely a great solution unless there's a reason why that value is special or performance for that value needs to be particularly good. Far better to get at the root problem of performance issues on that table, whether it is table bloat, insufficient indexes, invalid statistics, or something else.
