子查询返回的值超过1。当子查询遵循=，！=，<，<=，>，> =或时，不允许这样做

I'm getting an error

我收到了一个错误

Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression.Subquery