How Do I Fix the MySQL 'Illegal Mix of Collations' Error?

Troubleshooting "Illegal Mix of Collations" Error in MySQL

When encountering the error "Illegal mix of collations" in MySQL, it often indicates an incompatibility in collations when comparing or combining strings. This occurs when data with different character sets and collation rules are mixed, resulting in the error.

To resolve this issue, it is necessary to specify a shared collation for the columns being compared or selected. This can be achieved using the COLLATE clause, which allows you to specify the collation to be used within a query.

For example, to resolve the error in the given scenario, you could use the following query:

SELECT * FROM table ORDER BY key COLLATE latin1_general_ci;

This query ensures that the key column is sorted using the latin1_general_ci collation, matching the collation of the table.

Another option is to use the BINARY operator, which casts the strings to a binary format before comparison. This is a shorthand for CAST(str AS BINARY) and can be used as follows:

SELECT * FROM table WHERE BINARY a = BINARY b;

By casting the values to binary, any differences in collation rules are ignored, allowing for correct comparison.

It is important to note that casting values to binary might result in ignoring any indexes on those columns. For more detailed information, refer to the highly recommended answer provided by eggyal for this specific issue.

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