Insert into a MySQL table or update if exists

Posted by Rohit Kumar | Updated on

In this example, I have shared Insert into a MySQL table or update if exists. If you specify an ON DUPLICATE KEY UPDATE clause and a row to be inserted would cause a duplicate value in a UNIQUE index or PRIMARY KEY, an UPDATE of the old row occurs. For example, if column a is declared as UNIQUE and contains the value 1, the following two statements have similar effect:

Instead, use an equivalent statement that rewrites the UNION as a derived table:

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