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Description

This error indicates that MySQL attempted to convert data from one column type to another but failed because the conversion was not possible or resulted in data loss. It commonly occurs during replication, data loading, or when altering table schemas.

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Error Message

Column %d of table '%s.%s' cannot be converted from type '%s' to type '%s'

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Known Causes

3 known causes

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Schema Mismatch in Replication

The data types for a specific column differ between the source and replica tables, making direct conversion impossible during replication.

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Incompatible Data Type Cast

An explicit CAST operation or an implicit conversion attempts to transform data into an incompatible target type, such as converting non-numeric text to an integer.

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Data Truncation or Overflow

The data being converted exceeds the maximum length or value capacity of the target column's data type, leading to a conversion failure.

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Solutions

3 solutions available

1. Identify and Correct Data Mismatch medium

Locate rows with incompatible data for the target column type and either correct or remove them.

1

Determine the exact column and table involved in the error message.

2

Examine the data in the source column to identify values that cannot be converted to the target data type. For example, if converting to an integer and the source column contains text or invalid numeric formats.

SELECT * FROM your_database.your_table WHERE your_column_name NOT REGEXP '^[0-9]+$'; -- Example for numeric conversion

3

Correct the incompatible data. This might involve updating the offending rows to a valid format or removing them if they are erroneous.

UPDATE your_database.your_table SET your_column_name = 'corrected_value' WHERE some_condition;

4

Alternatively, if the data is truly unrecoverable or not needed, delete the problematic rows.

DELETE FROM your_database.your_table WHERE some_condition;

5

Once the data is clean, re-attempt the operation that caused the error (e.g., ALTER TABLE, INSERT, UPDATE).

2. Adjust Target Data Type easy

Modify the target column's data type to be more accommodating of the existing data.

1

Understand the intended use of the column and the nature of the data it holds.

2

If the target data type is too restrictive (e.g., trying to convert a VARCHAR with mixed content to INT), consider a more flexible type like VARCHAR, TEXT, or a numeric type with a larger range or decimal places.

ALTER TABLE your_database.your_table MODIFY COLUMN your_column_name VARCHAR(255); -- Example: changing to a more flexible VARCHAR

3

If converting to a numeric type, ensure it can accommodate the range and precision of the existing data. For instance, if converting to INT but the data has large numbers, consider BIGINT.

ALTER TABLE your_database.your_table MODIFY COLUMN your_column_name BIGINT; -- Example: changing to BIGINT

4

After altering the column type, re-attempt the operation that failed.

3. Use Intermediate Column for Complex Conversions advanced

Employ a temporary column to facilitate complex data type transformations.

1

Add a new, temporary column with a data type that can safely receive the source data.

ALTER TABLE your_database.your_table ADD COLUMN temp_column VARCHAR(255);

2

Copy the data from the source column to the temporary column, performing any necessary data cleaning or transformation during the copy.

UPDATE your_database.your_table SET temp_column = CAST(your_column_name AS UNSIGNED); -- Example: casting to unsigned, adjust as needed

3

If the cast in the previous step failed for some rows, you will need to identify and fix those rows in the source column or the temp column before proceeding.

4

Once the data is successfully copied and transformed into the temporary column, you can then alter the original column to the desired target type.

ALTER TABLE your_database.your_table MODIFY COLUMN your_column_name INT; -- Example: changing original to INT

5

Copy the data back from the temporary column to the now correctly typed original column.

UPDATE your_database.your_table SET your_column_name = temp_column;

6

Drop the temporary column.

ALTER TABLE your_database.your_table DROP COLUMN temp_column;

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Related Errors

5 related errors

MySQL Error 1677: Column Type Conversion Failed