Error
Error Code:
1271
MySQL Error 1271: Illegal Collation Mix
Description
This error indicates that MySQL encountered columns or string literals with different character sets or collations during an operation. This typically happens when comparing, combining, or performing calculations on data that has incompatible collation settings, preventing the operation from completing successfully.
Error Message
Illegal mix of collations for operation '%s'
Known Causes
4 known causesInconsistent Table Collations
Performing operations like JOIN or UNION between tables where the corresponding columns have different character sets or collations.
Mismatched Comparison Collations
Comparing or sorting string data with different collations in WHERE, ORDER BY, or GROUP BY clauses, causing an ambiguity for MySQL.
Function Argument Collations
Using string manipulation functions (e.g., CONCAT, LIKE, INSTR) where the input arguments or involved columns have conflicting collations.
Implicit Collation Conversion
MySQL's attempt to implicitly convert collations during an operation fails due to fundamental incompatibilities between the involved character sets or collations.
Solutions
3 solutions available1. Explicitly Specify Collation in Queries easy
Force a consistent collation for problematic string comparisons within a query.
1
Identify the column or expression causing the collation mix. This is often within a `WHERE`, `JOIN`, `ORDER BY`, or `GROUP BY` clause.
2
Use the `COLLATE` clause to enforce a specific collation on one of the operands. Choose a collation that is compatible with both sides of the comparison. A common and safe choice is `utf8mb4_unicode_ci` or `utf8mb4_general_ci` if you are using UTF-8.
SELECT * FROM table1 JOIN table2 ON table1.column1 COLLATE utf8mb4_unicode_ci = table2.column2;3
Alternatively, if you are comparing a column to a literal string, ensure the literal string also uses the same collation.
SELECT * FROM your_table WHERE your_column = 'your_string' COLLATE utf8mb4_unicode_ci;2. Alter Table to Standardize Column Collations medium
Modify table schema to ensure all relevant columns use a consistent collation.
1
Identify the tables and columns involved in the operation that is causing the error. You can often infer this from the query that triggered the error.
2
Determine the desired default collation for your database or specific tables. A good practice is to use `utf8mb4_unicode_ci` for broad character support.
3
Alter the table to change the collation of the problematic columns. This is a more permanent solution.
ALTER TABLE your_table MODIFY your_column VARCHAR(255) COLLATE utf8mb4_unicode_ci;4
If you are changing the collation of many columns or tables, consider altering the default collation for the database or even the server. **Caution**: Changing server defaults can have wide-ranging impacts. Back up your data before making such changes.
ALTER DATABASE your_database CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;3. Set Session Collation for Temporary Consistency easy
Temporarily set the collation for the current database session to resolve the issue for a series of queries.
1
Determine the desired collation that will be used for comparisons within your session. `utf8mb4_unicode_ci` is a common choice.
2
Before executing the problematic queries, set the session collation.
SET NAMES 'utf8mb4' COLLATE 'utf8mb4_unicode_ci';3
Execute your queries. The session's collation will be used for comparisons.
4
The session collation will revert when the connection is closed.