我有聯合主鍵(X,Y,Z)和表的額外條目時我秀創建表確實MySQL的節目創建表顯示KEY
`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`)
爲什麼我們得到KEY 'Y' ('Y')
和KEY 'Z' ('Z')
?這是否意味着什麼?