Storing text correctly.
WHAT A CHARACTER SET IS
The set of characters that can be stored, and how they are encoded.
WHAT A COLLATION IS
The rules for comparing and sorting them.
WHAT TO USE
A full modern encoding supporting every character, including symbols outside the basic range.
WHY THE DISTINCTION MATTERS IN MYSQL
An older encoding named as if it were complete stores only part of the range.
WHAT THAT BREAKS
Characters outside the basic range, which are silently rejected or truncate the value.
WHAT TO USE INSTEAD
The four-byte variant.
WHERE THE SETTING APPLIES
The server The database The table The column The connection
WHY THE CONNECTION MATTERS MOST
Correct storage with a wrong connection setting corrupts on the way in or out.
WHAT CORRUPTION LOOKS LIKE
Accented and non-Latin characters appearing as nonsense.
WHY IT IS FREQUENTLY PERMANENT
Once stored wrongly, the original bytes are gone.
WHAT TO CHECK ON ANY MIGRATION
That the dump, the import and the connection all agree.
WHAT COLLATION AFFECTS
Whether comparisons are case-sensitive Sort order Which values are considered equal
WHY THAT CAN SURPRISE
Two visually different strings may compare as equal.
WHAT TO KEEP CONSISTENT
Collation across columns that are joined.
WHY
Mismatched collations prevent index use on the join.
