Благодаря за актуализирането на заявката; сега можем да видим, че условието WHERE се прилага само към последното UNIONed заявка. Трябва да и двете добавете тази клауза WHERE към всяка заявка или я обвийте като подселекция и приложете клаузата WHERE към нея.
select s.id as id, s.email as email, s.password as password, s.role as role from tblStudents s
where email = "[email protected]"
union
select a.id as id, a.email as email, a.password as password, a.role as role from tblAdmin a
where email = "[email protected]"
union
select t.id as id, t.email as email, t.password as password, t.role as role from tblTeachers t
where email = "[email protected]"
или
SELECT * FROM (
select s.id as id, s.email as email, s.password as password, s.role as role from tblStudents s
union
select a.id as id, a.email as email, a.password as password, a.role as role from tblAdmin a
union
select t.id as id, t.email as email, t.password as password, t.role as role from tblTeachers t
) foo where email = "[email protected]"
