MySQL 8.0 Reference Manual Including MySQL NDB Cluster 8.0

10.9.1 The utf8mb4 Character Set (4-Byte UTF-8 Unicode Encoding)

The utfmb4 character set has these characteristics:

utf8mb4 contrasts with the utf8mb3 character set, which supports only BMP characters and uses a maximum of three bytes per character:

utf8mb4 is a superset of utf8mb3, so for an operation such as the following concatenation, the result has character set utf8mb4 and the collation of utf8mb4_col:

SELECT CONCAT(utf8mb3_col, utf8mb4_col);

Similarly, the following comparison in the WHERE clause works according to the collation of utf8mb4_col:

SELECT * FROM utf8mb3_tbl, utf8mb4_tbl
WHERE utf8mb3_tbl.utf8mb3_col = utf8mb4_tbl.utf8mb4_col;

For information about data type storage as it relates to multibyte character sets, see String Type Storage Requirements.