一些常用高效的oracle语句

-（高效） 0.187
SELECT *
  FROM hr.employees emp --(基础表)
 WHERE emp.employee_id > 0
   AND EXISTS (SELECT 'X'
          FROM hr.departments dept
         WHERE DEPT.Department_Id = EMP.Department_Id
           AND dept.location_id = 2400)
 
(低效)
SELECT *
  FROM hr.employees emp --(基础表) 
 WHERE emp.employee_id > 0
   AND EMP.Department_Id IN
       (SELECT Department_Id
          FROM hr.departments dept
         WHERE dept.location_id = 1100)

select emp.first_name , emp.employee_id
from hr.employees emp
where emp.first_name like '%\_%' escape '\'

--左模糊
select emp.first_name , emp.employee_id
from hr.employees emp
where emp.first_name like '%e'

--右模糊
select emp.first_name , emp.employee_id
from hr.employees emp
where emp.first_name like 'E%'