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SELECT fullname FROM people WHERE age = ?

April 26, 2017age fullname people select

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SELECT fullname FROM people WHERE age = ?

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Binding an undef (NULL) to the placeholder will not select rows which have a NULL age! At least for database engines that conform to the SQL standard. Refer to the SQL manual for your database engine or any SQL book for the reasons for this. To explicitly select NULLs you have to say “WHERE age IS NULL”. A common issue is to have a code fragment handle a value that could be either defined or undef (non-NULL or NULL) at runtime.