mysql - 在加入 Sql 之间时如何用例

Question

如何编写这样的查询:

SELECT * FROM table1 t1
    case when @id=1 then
        join table2 t2 on t1.id=t2.t1id
    else
        join table3 t3 on t1.id=t3.t1id
    end t1

请帮忙

Answer 1

这有帮助吗？

    SELECT * FROM table1 t1
    LEFT join table2 t2 on t1.id=t2.t1id and @id=1
    Left join table3 t3 on t1.id=t3.t1id and @id<>1