19 lines
566 B
SQL
19 lines
566 B
SQL
# 笛卡尔积
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SELECT * FROM dept,emp
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# 内连接
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SELECT * FROM dept INNER JOIN emp ON dept.`did`=emp.`edid`
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#另一中写法
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SELECT * FROM dept,emp WHERE dept.`did`=emp.`edid`
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#左外连接
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SELECT * FROM dept LEFT JOIN emp ON dept.`did`=emp.`edid`
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# 右外连接
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SELECT * FROM dept RIGHT JOIN emp ON dept.`did`=emp.`edid`
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#A or B表独有的
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SELECT * FROM dept RIGHT JOIN emp ON dept.`did`=emp.`edid`
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WHERE dept.`did`IS NULL
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#A和B全都有
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SELECT * FROM dept LEFT JOIN emp ON dept.`did`=emp.`edid`
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UNION
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SELECT * FROM dept RIGHT JOIN emp ON dept.`did`=emp.`edid`
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