How to Identify UTF-8 Characters in Latin1-Encoded Database Columns?

Identifying UTF-8 Characters in Latin1-Encoded Columns

In the task of database conversion from Latin1 to UTF-8, it's crucial to assess the presence of UTF-8 characters in Latin1 columns. Here are the suggested approaches:

Option 1: Perl Script to Detect UTF-8

Performing a MySQL dump and using Perl to search for UTF-8 characters can be effective. UTF-8 characters are typically represented as a sequence of bytes with high-order bits set to 1. The Perl script can scan the dump file for byte patterns that match this pattern.

Option 2: MySQL CHAR_LENGTH Comparison

Using MySQL CHAR_LENGTH to find rows with multi-byte characters is a valid approach. However, it may not be conclusive. Latin1 characters like accented characters may also have multiple bytes.

Recommended Method: Visual Comparison

To accurately determine the encoding, it is recommended to use a visual comparison method:

SELECT CONVERT(CONVERT(name USING BINARY) USING latin1) AS latin1,
       CONVERT(CONVERT(name USING BINARY) USING utf8) AS utf8 
FROM users 
WHERE CONVERT(name USING BINARY) RLIKE CONCAT('[', UNHEX('80'), '-', UNHEX('FF'), ']')

This query identifies rows where the binary representation of 'name' contains high-ASCII characters that could be either Latin1 accents or UTF-8 multi-byte characters. By comparing the 'latin1' and 'utf8' columns visually, you can distinguish between Latin1 and UTF-8 characters.

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