【面試虐菜】—— 常用SQL語句

創建表

create table emp(

id decimal,

name char(10),

age decimal)

 

刪除表

DROP TABLE EMP

 

插入默認值

CREATE TABLE EMP(

　　Id decimal NOT NULL,

　　Name char(10) NOT NULL,

　　Age decimal NOT NULL DEFAULT 18)

 

添加列

ALTER TABLE EMP ADD COLUMN Comments char(50) NOT NULL DEFAULT 'COMMENTS'

 

刪除列

ALTER TABLE EMP DROP COLUMN Comments

 

修改列

ALTER TABLE EMP MODIFY COLUMN Comments char(30)

 

創建索引

CREATE INDEX Name_index ON EMP (Name)

 

查詢數據

SELECT Name FROM EMP

 

查詢不重復的數據

SELECT DISTINCT Name FROM EMP

 

對查詢結果排序

SELECT Name FROM EMP ORDER BY Name

 

條件查詢

SELECT Name FROM EMP WHERE Age < 20

SELECT Name FROM EMP WHERE Age BETWEEN 20 AND 30

 

插入數據

INSERT INTO EMP VALUES(123,'xingoo',18)

 

修改數據

UPDATE EMP SET Name='xingoo1111' WHERE Name='xingoo'

 

刪除數據

DELETE FROM EMP WHERE Age<20

 

求平均數

SELECT AVG(Age) FROM EMP

 

查詢條數

SELECT COUNT(DISTINCT Name) FROM EMP

SELECT COUNT(*) FROM EMP