between and 關鍵字

案例1:查詢員工編號在100到120之間的員工資訊

SELECT
         *
FROM 
      employees
WHERE
      employee_id >=100 AND employee_id<=120;

使用between and

SELECT
         *
FROM 
      employees
WHERE
      employee_id BETWEEN  100  AND 120;

注意事項

案例:查詢員工的工種編號是 IT_PROG、AD_VP、AD_PRES中的一個員工名和工種編號

select
         last_name,
         job_id
from 
      employees
where
      job_id='IT_PROT' or job_id='AD_VP' or job_id='AD_PRES';
 

用in關鍵字

select
         last_name,
         job_id
from 
      employees
where
      job_id in ('IT_PROT' ,'AD_VP' , 'AD_PRES');

注意事項：

查詢沒有獎金的員工名和獎金率

SELECT
         last_name,
         commission_pct
FROM 
      employees
WHERE
      commission_pct IS NULL;

查詢有獎金的員工名和獎金率

SELECT
         last_name,
         commission_pct
FROM 
      employees
WHERE
      commission_pct IS NOT NULL;
 

安全等於 <=>

用於判斷等於

SELECT
         last_name,
         commission_pct
FROM 
      employees
WHERE
      commission_pct <=> NULL;

案例二：查詢工資為12000的員工資訊

SELECT
         last_name,
         salary
FROM 
      employees
WHERE
      salary <=> 12000;

PK

查詢沒有獎金，且工資小於18000的salary，last_name

SELECT
         salary,
         last_name
FROM 
      employees
WHERE
      salary < 18000
AND
      commission_pct IS NULL;
 

查詢部門departments表中涉及到了哪些位置編號（涉及另一個表）

其中desc是用於去重

經典面試題

複習