Error code: 1242 Subquery returns more than 1 row, 1242 subquery

Error code: 1242 Subquery returns more than 1 row, 1242 subquery
1. Error description

1 queries executed, 0 success, 1 errors, 0 warnings query: SELECT t. id, DATE_FORMAT (t. statisTime, '% Y-% m-% d % H: % I: % s') statisTime, (SELECT 'id' FROM t_truck_info WHERE id = t. plateId... error code: 1242 Subquery returns more than 1 row execution time: 0.009 sec Transfer Time: 0.002 sec total time: 0.012 sec

2. Cause of error

When writing a query SQL statement, one of the fields is obtained from another table.

Select t. id, (select num from t_user_info where id = stuNo) as amount from t_stu_info t left join t_user_info t0on t0.id = t. stuNo

The query results show that num contains multiple data records, while the outer query results require num to be one data record.

3. Solution

Select t. id, (select sum (num) from t_user_info where id = stuNo) as amount from t_stu_info t left join t_user_info t0on t0.id = t. stuNo

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