SQL基础--基础语句和运算

SQL基础–基础语句和运算

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1 .SELECT 语句 查询语句

SELECT * FROM EMPLOYEES e;

2 .UPDATE 语句 更新语句

UPDATE EMPLOYEES SET LAST_NAME = 'AAA' WHERE EMPLOYEE_ID = 100;

3 .DELETE 语句 删除语句

DELETE FROM EMPLOYEES e WHERE e.EMPLOYEE_ID = 100;

4 .INSERT 语句 * 插入语句*

INSERT INTO EMPLOYEES VALUES(...);  ---只能插入单行

5 .DDL 语句 数据库定义语句

CREATE...DROP...ALTER...TRUNCATE...

6 .DCL 语句 数据库控制语句

COMMITSAVEPOINT XXXROLLBACK

7 .运算

+ - * /   加减乘除mod（a,b） 取模power(a,b) a^bROUND(原始值,小数点位数（可为负）) 四舍五入ceil(a)    向上取整floor(b)   向下取整

8 .比较

> >= < <= <> != BETWEEN ... AND ...(包括起始值)IN （SET）IS NULL、NOT ... IS NULLLIKE (%、ESCAPE)