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We have a clustered index in table Tbl with order of A,B,C. Does it make senses to write a query to have

WHERE A = @a, B = @b, C = @c

or it'll be as same as

WHERE C = @c, B = @b, A = @a

Does the order of query make sense for clustered index?

  • 1
    And you have to use AND, not commas, between the conditions in WHERE. – ypercubeᵀᴹ Aug 7 '14 at 8:55
6

It makes no difference: the optimiser evaluates the query and will work out predicate order for itself, matching a suitable index and all the other good stuff it does.

This is because SQL is "declarative" not "procedural": you say what you want, not how to do it.

It's nicer to read though...

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Actually when we use the where clase then sql creates seperate pages for each where clause. then its make join based on AND , OR and then produce the output. So, here switching the where clause is not a matter.

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