Don't Use SELECT *

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Don't Use SELECT *

published 4 months, 25 days ago, submitted by misbaharefin 4 months, 26 days ago

dotnethitman.spaces.live.com — I've seen many developers actually using and abusing SELECT * FROM queries. SELECT * query not only returns unnecessary data, but it also can force clustered index scans for query plans because columns in the SELECT clause are also considered by the optimizer when it identifies indexes for execution plans.

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Comments:

as good as this advice is the first execution plan has nothing to do with the * itself.
It is showing a bookmark lookup that will happen for every query when you're filtering on a column that has a non clustered index and
columns in the select list that are not covered by a non clustered index.
because data is stored in the leaf level of the CI a bookmark look up is looking up that data in the CI.

just to clear thing up :))

other than that the advice is sound!

posted by spirit1 4 months, 25 days ago