思维导图
day10数据库备份.png4个连接在一起
SELECT *
FROM
(
(
(
students st
JOIN scores sc
ON st.sno
= sc.sno
)
JOIN courses co
ON sc.cno
= co.cno
)
JOIN teachers te
ON te.tno
= co.tno
);
SELECT *
FROM
(
(
(
students st
JOIN scores sc
ON st.sno
= sc.sno
)
JOIN courses co
ON sc.cno
= co.cno
)
JOIN teachers te
ON te.tno
= co.tno
);
本文标题:2018-10-26数据库备份
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