Finding Table Differences on Nullable Columns Using MySQL Generated Columns

Some time ago, a customer had a performance issue with an internal process. He was comparing, finding, and reporting the rows that were different between two tables. This is simple if you use a LEFT JOIN and an IS NULL comparison over the second table in the WHERE clause, but what if the column could be null? That is why he used UNION, GROUP BY and a HAVING clauses, which resulted in poor performance. The challenge was to be able to compare each row using a LEFT JOIN over NULL values.

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database,tutorial,mysql,sysbench,mysql generated columns,nullable columns