Does SELECT * create additional overhead even when you want all columns?

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Question :

I have read that SELECT * is typically undesirable in that it creates additional overhead. Is this the case if you want to retrieve all columns?

I have a extremely badly performing queries, which is made up of nested ‘SELECT *’ queries. In all cases I do want all the columns returned to me though…

Answer :

Strictly answering your question, no there is no additional overhead when you want all columns returned. But it is undesirable as you mentioned. I do not want to reiterate why it is undesirable as most of the points are discussed in this answer.

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