How to Detect UTF-8 Characters in Latin1 Encoded MySQL Columns?

Detecting UTF-8 Characters in Latin1 Encoded Columns in MySQL

Problem:

You want to determine if Latin1 encoded columns in your database contain UTF-8 characters before converting the database to UTF-8.

Option 1: MySQL Dump and Perl Search

This option involves using a MySQL dump to create a text file and then using Perl to search for UTF-8 characters. However, this method can be time-consuming and inefficient for large datasets.

Option 2: MySQL CHAR_LENGTH Comparison

This option uses the MySQL CHAR_LENGTH function to find rows with multi-byte characters, which may indicate the presence of UTF-8 characters. However, it may not be sufficient as some Latin1 accented characters are also multi-byte.

Suggested Solution:

A more comprehensive approach is to use the following query:

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 searches for "high-ASCII" characters that could be either Latin1 accented characters or UTF-8 multi-byte characters. By converting the binary representation of the name using both Latin1 and UTF-8 encodings, you can compare the results visually and determine if there are any differences, indicating the presence of UTF-8 characters.

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