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Asked: 2026-05-27T18:38:13+00:00

I’m using binary string comparison on user names (defined as varchar) to be sure

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I’m using binary string comparison on user names (defined as varchar) to be sure the string matches exactly:

... where binary Owner = '$user' ...

or 

... from Records join Users on binary Records.Owner = Users.User ....

But I’m not sure if it has some (either positive or negative) impact on efficiency. The manual states:

Note that in some contexts, if you cast an indexed column to BINARY,
MySQL is not able to use the index efficiently.

Is it an issue in this case? I would expect binary to be faster on the contrary, because it doesn’t have to ignore case, whitespace, some accents etc.

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  1. Editorial Team

    Indeed, it’s possible for an expression in a WHERE clause to make it impossible to use an index on a column. You wouldn’t expect an index on a float column called x to be any use for searching

    WHERE SIN(x) BETWEEN 0.0 and 0.1

    for example.

    The answer to your problem is to define your Owner column to have a binary collation rather than a case-insensitive collation. See here for how to do that: http://dev.mysql.com/doc/refman/5.0/en/charset-column.html

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