mysql - 在子查询返回多行的情况下对值求和。 (我的用例是 2 行)

Question

我有多个行通过查询。如何对这些行进行分组以总结某些行的值并保留其余行。

set total_fees1 = (select (f.total_Fees2) from fee_Collection f where f.student_Id =minstudent_Id);
            set total_fees2 = (select (f.total_Fees3) from fee_Collection f where f.student_Id =minstudent_Id);
            set paid_amount1 = (select (f.paid_amount2) from fee_Collection f where f.student_Id =minstudent_Id);
            set paid_amount2 = (select (f.paid_amount3) from fee_Collection f where f.student_Id =minstudent_Id);

在某些情况下，上述查询会返回 2 行。现在，如果我获得的行数超过 1 行，我必须添加paid_amount 值，并获取total_fees 字段的第一行值。

Answer 1

那就是:

set total_fees1 = (select (f.total_Fees2) from fee_Collection f where f.student_Id =minstudent_Id LIMIT 1);
        set total_fees2 = (select (f.total_Fees3) from fee_Collection f where f.student_Id =minstudent_Id LIMIT 1);
        set paid_amount1 = (select SUM(f.paid_amount2) from fee_Collection f where f.student_Id =minstudent_Id);
        set paid_amount2 = (select SUM(f.paid_amount3) from fee_Collection f where f.student_Id =minstudent_Id);