我有一张表,它的主键是由 (X,Y,Z) 组成的联合主键。当我执行 show create table 命令时,会显示以下内容:
`X` int(10) unsigned NOT NULL,
`Y` int(10) unsigned NOT NULL,
`Z` int(11) NOT NULL,
`C` bigint(20) NOT NULL,
PRIMARY KEY (`X`,`Y`,`Z`),
KEY `Y` (`Y`),
KEY `Z` (`Z`),
CONSTRAINT `T_ibfk_1` FOREIGN KEY (`X`) REFERENCES `X_T` (`X`),
CONSTRAINT `T_ibfk_2` FOREIGN KEY (`Y`) REFERENCES `Y_T` (`ID`),
CONSTRAINT `T_ibfk_3` FOREIGN KEY (`Z`) REFERENCES `Z_T` (`Z`)
为什么我们会得到 KEY 'Y' ('Y')
和 KEY 'Z' ('Z')
?这是否暗示着什么?