sql

Posted 2021-03-15 null

INSERT TAB_NAME(字段名称..) VALUES(值....) WHERE (添加条件)
UPDATE TAB_NAME SET 字段名称=

UPDATE user SET age=25 WHERE id=1;
DELETE FORM TAB_NAEM WHERE (添加条件)
DELETE FORM user WHERE age>=24
//删除数据，不加条件，删除所有数记录，AUTO_INCREMENT不会重置
SHOW CREAEAT TABLE TBA_NAME //查询表条件
修改表结构  ALTER
ALTER TABLE TAB_NAME AUTO_INCREMENT=1

TAUNCATE TAB_NAME彻底清空精数据

查询记录
SELECT  FORM TAB_NAE 
    [WHERE 条件]
    [GROUP BY (COL_NAME) HAVING 二次筛选] 
    [GRDER BY (COL_NAME) BY (ASC|DESC)] 
    [LIMT限制结果集的显示条数] 

SELECT * FROM TAB_NAME //查询表中所有字段

SELECT username,addr,age FROM TAB_NAME //查询指定字段
SELECT * FORM king.user //查询king下的user表

给字段起别名
SELECT 字段名 AS 别名 FROM TBA_NAME 
SELECT id AS ‘编号‘,username AS ‘用户名‘ FROM user;
给数据表取别名
SELECT TAB_NAME FORM TAB_NAME AS 别名
SELECT id,userName,age FROM user AS u
表名.字段名
SELECT TAB_NAME.COL.NAME FROM TBA_NAME;
SELECT user1.id,user1.userName,user1.age FROM user1
条件查询 比较运算符
SELECT id,username,age FROM user WHERE id=5;


ALTER TABLE user1 ADD 添加的字段 VARCHAR(100)


查询用户userDesc 为null的用户
SELECT id,userName,age,userDesc FROM user1 WHERE userDesc<=>NULL

检测null (IS NOT NULL)
SELECT id,userName,userDesc FROM user WHERE userDes IS NULL

查询范围 BETWEEN AND | NOT BETWEEN START AND END
舍近求远年龄18-30的用户
SELECT id,userName,age,sex FROM age BETWEEN 18 AND 30;

查询指定集合 IN
SELECT id,uerName,age FROM user1 WHERE id IN (1,3,5,7,29,45,78)

逻辑运算符AND RO

SELECT id,userName,age,sex FROM user1 WHERE sex=‘男‘ AND age>20;
SELECT id,userName,age,sex FROM user1 WHERE id=‘1‘ AND

匹配字符 模糊查询 like
SELECT id,userName,age,sex FROM suer1 WEERE username LIKE ‘king‘;
结合通配符查询 %匹配多个， _匹配单个占位符
SELECT id,userName,age,sex FROM user1 WHERE username LIKE ‘%三%‘
查询以风为结尾的用户
SELECT id,userName,age,sex FROM user1 WHERE username LIKE ‘%风‘
查询以风为开头的用户
SELECT id,userName,age,sex FROM user1 WHERE username LIKE ‘风%‘
查询三位的用户
SELECT id,userName,age,sex FROM user1 WHERE username LIKE ‘___‘