有如下三张表： user表: ID 姓名 年龄 1 aaa 12 2 bbb 13 3 ccc 15 4 ddd 16
举报类型表 ID 类型 1 色情 2 诈骗
举报信息列表 ID 举报人ID 被举报人ID 举报类别ID 1 1 2 1 2 3 2 1 3 4 2 2
需查询：举报人姓名 被举报人姓名 举报类别
求教给位大神改怎么写sql!!
Suppose the three tables are tables A, B, and C;
Select a1.name, a2.name, b.type from A a1, A a2, B b, C c where a1.id=c.userId1 and a2.id=c.userId2 and b.id=c.typeId
Correct answer upstairs. Provide another way of writing, SELECT a1.name, a2.name, b.type FROM C c LEFT JOIN b c.typeId = b.id LEFT JOIN A a1 ON a1.id=c.userId1 LEFT JOIN A a2 ON a2.id=c.userId2;
SELECT a1.name, a2.name, b.type FROM C c LEFT JOIN b c.typeId = b.id LEFT JOIN A a1 ON a1.id=c.userId1 LEFT JOIN A a2 ON a2.id=c.userId2;
Several connections in SQL: inner join, left join, right join, full join, cross join: http://www.ido321.com/1061.html
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Suppose the three tables are tables A, B, and C;
Correct answer upstairs.
Provide another way of writing,
SELECT a1.name, a2.name, b.type FROM C c LEFT JOIN b c.typeId = b.id LEFT JOIN A a1 ON a1.id=c.userId1 LEFT JOIN A a2 ON a2.id=c.userId2;Several connections in SQL: inner join, left join, right join, full join, cross join: http://www.ido321.com/1061.html