When attempting to change a MySQL table's collation to utf8_general_cs, many developers encounter the error:

ERROR 1273 (HY000): Unknown collation: 'utf8_general_cs'

This occurs because utf8_general_cs is not a built-in collation in MySQL. The confusion often comes from the fact that MySQL has case-sensitive collations, but they follow different naming conventions.

For UTF8 character sets, MySQL provides these case-sensitive alternatives:

utf8_bin
utf8_unicode_ci (case-insensitive)
utf8_general_ci (case-insensitive)

To verify available collations in your MySQL installation, run:

SHOW COLLATION WHERE Charset = 'utf8';

For case-sensitive comparisons, use utf8_bin which performs binary comparisons:

ALTER TABLE table_name 
CONVERT TO CHARACTER SET utf8 
COLLATE utf8_bin;

If you specifically need the general collation with case sensitivity, you might need to:

-- First change to binary
ALTER TABLE table_name 
CONVERT TO CHARACTER SET utf8 
COLLATE utf8_bin;

-- Then create a custom collation if needed
-- (This requires MySQL 8.0+ and server configuration)

If you need case-sensitive behavior for specific queries without changing the table collation:

SELECT * FROM table_name 
WHERE column_name COLLATE utf8_bin = 'SearchTerm';

In newer MySQL versions, utf8mb4 is preferred over utf8:

ALTER TABLE table_name 
CONVERT TO CHARACTER SET utf8mb4 
COLLATE utf8mb4_bin;

The utf8mb4 character set supports the full Unicode character set including emojis and is generally recommended for modern applications.

If you encounter further problems:

1. Check your MySQL version: SELECT VERSION();
2. Verify character sets: SHOW CHARACTER SET;
3. Check table current collation: SHOW CREATE TABLE table_name;

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When attempting to change a MySQL table's collation to utf8_general_cs, you might encounter the error "Unknown collation: 'utf8_general_cs'". This occurs because this specific case-sensitive collation isn't available by default in modern MySQL installations. The utf8_general_ci (case-insensitive) variant is commonly available, but the case-sensitive version was deprecated and removed in newer MySQL versions.

First, verify which collations are actually available in your MySQL installation:

SHOW COLLATION WHERE Charset = 'utf8';

You'll typically see collations like:

• utf8_general_ci
• utf8_bin
• utf8_unicode_ci

If you specifically need case-sensitive collation, consider these alternatives:

Option 1: Use utf8_bin

The binary collation provides case-sensitivity:

ALTER TABLE table_name 
CONVERT TO CHARACTER SET utf8 
COLLATE utf8_bin;

Option 2: Upgrade to utf8mb4

For newer MySQL versions (5.5.3+), use utf8mb4 with its binary collation:

ALTER TABLE table_name 
CONVERT TO CHARACTER SET utf8mb4 
COLLATE utf8mb4_bin;

If migrating from an older system that used utf8_general_cs:

1. Test all string comparisons in your application
2. Verify sorting behavior matches expectations
3. Check any application code relying on case-sensitive matching

For MySQL 8.0+, you can potentially create a custom collation if absolutely needed:

CREATE COLLATION my_cs_collation (
  LOCALE = 'en_US.utf8',
  PROVIDER = 'icu',
  DETERMINISTIC = TRUE
);

However, this requires ICU library support and thorough testing.

Changing collation affects:

• Existing indexes (they will be rebuilt)
• Query performance (binary collations are generally faster)
• Storage requirements (may increase slightly)