子查询使用mysql返回多于1行

Question

我正在尝试从 MySQL 数据库中选择 id 用户（员工或领导或经理）和全名的 select 语句。取决于 id dept ， id priority 。代码是：

PROCEDURE `get_parent`(id_dept int, id_priorty int )
BEGIN
if(select employee_tb.id_dept  from employee_tb where (employee_tb.id_dept=id_dept&&3=id_priorty))>0
then
begin
select id_employee ,full_name,3 as type from employee_tb;
end;
elseif(select leader_tb.id_dept from leader_tb where (leader_tb.id_dept=id_dept&&id_priorty=2))>0
 then
 begin
 select id_leader, full_name, 2 as type from leader_tb;
 end;
 elseif(select manager_tb.id_dept from manager_tb where (manager_tb.id_dept=id_dept&&id_priorty=1))>0
 then 
 begin
 select id_manager, full_name, 1 as type from manager_tb;
 end;
 else
 select "failed"as result ;
 end if;
END

Answer 1

select id_employee ,full_name,3 as type from employee_tb;

select id_leader, full_name, 2 as type from leader_tb;

select id_manager, full_name, 1 as type from manager_tb;

检查条件后代码中的那 3 行无论如何都会选择表中的所有记录。

要解决这个问题：

PROCEDURE `get_parent`(id_dept int, id_priorty int )
BEGIN
if(select employee_tb.id_dept  from employee_tb where (employee_tb.id_dept=id_dept&&3=id_priorty))>0
then
begin
select id_employee ,full_name,3 as type from employee_tb where (employee_tb.id_dept=id_dept&&3=id_priorty);
end;
elseif(select leader_tb.id_dept from leader_tb where (leader_tb.id_dept=id_dept&&id_priorty=2))>0
 then
 begin
 select id_leader, full_name, 2 as type from leader_tb where (leader_tb.id_dept=id_dept&&id_priorty=2);
 end;
 elseif(select manager_tb.id_dept from manager_tb where (manager_tb.id_dept=id_dept&&id_priorty=1))>0
 then 
 begin
 select id_manager, full_name, 1 as type from manager_tb where (manager_tb.id_dept=id_dept&&id_priorty=1);
 end;
 else
 select "failed"as result ;
 end if;
END

如果有一条记录匹配这个where子句，它当然会给出一条记录。