创建表
create table emp( id decimal, name char(10), age decimal)
删除表
DROP TABLE EMP
插入默认值
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‘
删除列
ALTER TABLE EMP DROP COLUMN Comments
修改列
ALTER TABLE EMP MODIFY COLUMN Comments char(30)
创建索引
CREATE INDEX Name_index ON EMP (Name)
查询数据
SELECT Name FROM EMP
查询不重复的数据
SELECT DISTINCT Name FROM EMP
对查询结果排序
SELECT Name FROM EMP ORDER BY Name
条件查询
SELECT Name FROM EMP WHERE Age < 20 SELECT Name FROM EMP WHERE Age BETWEEN 20 AND 30
插入数据
INSERT INTO EMP VALUES(123,‘xingoo‘,18)
修改数据
UPDATE EMP SET Name=‘xingoo1111‘ WHERE Name=‘xingoo‘
删除数据
DELETE FROM EMP WHERE Age<20
求平均数
SELECT AVG(Age) FROM EMP
查询条数
SELECT COUNT(DISTINCT Name) FROM EMP SELECT COUNT(*) FROM EMP
原文：http://www.cnblogs.com/xing901022/p/3975705.html