VARCHARの最大長

CHAR(M)
ストレージ消費：M文字
最大：２５５文字

VARCHAR
ストレージ消費：M文字＋１または２バイト
最大：６５５３５バイト

実際のVARCHARの最大は、６５５３２バイト。

[test]> create table inno(a varchar(21845)) default character set utf8 engine=innodb;

ERROR 1118 (42000): Row size too large. The maximum row size for the used table type, not counting BLOBs, is 65535. You have to change some columns to TEXT or BLOBs

[test]> create table inno(a varchar(21844)) default character set utf8 engine=innodb;

Query OK, 0 rows affected (0.02 sec)

21844 * 3 = 65532

[test]> create table inno2(a varchar(65533)) default character set latin1 engine=innodb;

ERROR 1118 (42000): Row size too large. The maximum row size for the used table type, not counting BLOBs, is 65535. You have to change some columns to TEXT or BLOBs

[test]> create table inno2(a varchar(65532)) default character set latin1 engine=innodb;

Query OK, 0 rows affected (0.07 sec)

６５５３２＋２＝６５５３４

残り１バイトは？

ちなみに行の最大は６５５３５バイトという制限がある。

[test]> create table maxrow(a int, b varchar(65529)) default character set latin1 engine=innodb;

ERROR 1118 (42000): Row size too large. The maximum row size for the used table type, not counting BLOBs, is 65535. You have to change some columns to TEXT or BLOBs

[test]> create table maxrow(a int, b varchar(65528)) default character set latin1 engine=innodb;

Query OK, 0 rows affected (0.03 sec)

４＋６５５２８＝６５５３２