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How much of a performance benefit is there by selecting only required field in query instead of querying the entire row? For example, if I have a row of 10 fields but only need 5 fields in the display, is it worth querying only those 5? what is the performance benefit with this limitation vs the risk of having to go back and add fields in the sql query later if needed?
It’s not just the extra data aspect that you need to consider. Selecting all columns will negate the usefulness of covering indexes, since a bookmark lookup into the clustered index (or table) will be required.