Tweak Informix query

I have a bunch of Informix queries and I need to verify the performance of each query.

All these queries are long a开发者_开发问答nd contain a lot inner SELECT and JOINs. So I am wondering if there is any tool which can assist me to check which fragment in the query affects the whole query performance?

It would help a lot because it's hard to check only by eyes.

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If you want to analyze queries then use Informix SET EXPLAIN and analyze output file it creates. Have a look at IBM documentation: http://www.ibm.com/developerworks/data/library/techarticle/dm-0409fan/index.html?S_TACT=105AGX52&S_CMP=cn-a-db2