子查詢使用我的 sql 返回超過 1 行

Question

我正在嘗試創建一條 select 語句，從 MySQL 數據庫中選擇用戶 ID（員工或領導或經理）和全名。 取決於 id 部門，id 優先級。 代碼是：

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;

檢查條件后代碼中的那 3 行無論如何都會從表中選擇所有記錄。

要解決此問題：

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

如果有一條記錄匹配這個 where 子句，它當然會給出一條記錄。