--创建数据库 CREATE DATABASE Nuctech --删除数据库 DROP DATABASE Nuctech --创建表 CREATE TABLE Zhaocl(name VARCHAR(50),gender VARCHAR(50),age INT) --删除表 DELETE dbo.Zhaocl --删除表数据,不删除表结构,不释放空间 TRUNCATE TABLE dbo.Zhaocl --删除表数据,不删除表结构,释放空间 DROP TABLE dbo.Zhaocl --删除表所有,删除表结构,释放空间 --增加字段(列) ALTER TABLE dbo.Zhaocl ADD addr VARCHAR(50) --删除字段(列) ALTER TABLE dbo.Zhaocl DROP COLUMN age --插入数据 INSERT dbo.Zhaocl ( NAME, gender, addr ) VALUES ( 'zhaocl', -- NAME - varchar(50) 'men', -- gender - varchar(50) 'beijing' -- addr - varchar(50) ) --删除数据 DELETE FROM dbo.Zhaocl WHERE NAME = 'zhaocl' --(注意where条件,否则就删除所有数据了) --更新数据 UPDATE dbo.Zhaocl SET addr = 'zhengzhou' WHERE NAME = 'zhaocl' --(注意where条件,否则更新所有字段值) --查询表所有数据 SELECT * FROM dbo.Websites --查询某列数据 SELECT name FROM dbo.Websites --返回唯一不同的值 SELECT DISTINCT name FROM dbo.Websites --升序排列(默认ASC) SELECT * FROM dbo.Websites ORDER BY alexa --降序排列 SELECT * FROM dbo.Websites ORDER BY alexa DESC --获取第一条数据 SELECT TOP 1 NAME,url FROM dbo.Websites --获取最后一条数据 SELECT TOP 1 name FROM dbo.Websites ORDER BY name DESC --获取某列最大值 SELECT MAX(alexa) AS maxAlexa FROM dbo.Websites --获取某列最小值 SELECT MIN(alexa) AS minAlexa FROM dbo.Websites --某列求和(varchar类型的不可) SELECT SUM(name) AS sumAlexa FROM dbo.Websites --字母转大写 SELECT UPPER(country) FROM dbo.Websites --字母转小写 UPDATE dbo.Websites SET country = LOWER(country) --字符串截取 SELECT SUBSTRING(country,1,3) FROM dbo.Websites --获取字符串长度 SELECT LEN(country) AS lenCountry FROM dbo.Websites WHERE alexa=13 --四舍五入 SELECT ROUND(1.56,1) --第三个参数非0时,表示舍弃位数,不再进行四舍五入 SELECT ROUND(2.56,1,1) --获取当前时间 SELECT GETDATE() --获取当前年月日 SELECT DATENAME(YEAR,GETDATE()) SELECT DATENAME(MONTH,GETDATE()) SELECT DATENAME(DAY,GETDATE()) SELECT YEAR(GETDATE()) --FORMAT格式化 SELECT FORMAT(GETDATE(),'yyyy-MM-dd') --对结果集分组,并对组进行操作(SUM) SELECT country,SUM(alexa) AS sumAlexa FROM dbo.Websites GROUP BY country --where无法和聚合函数一起使用,所以使用HAVING跟条件 SELECT country,AVG(alexa) AS avgAlexa FROM dbo.Websites GROUP BY country HAVING country = 'china' --LIKE SELECT country FROM dbo.Websites WHERE country LIKE '%a%' --包含a(SQL不区分大小写) SELECT country FROM dbo.Websites WHERE country LIKE '%a' --a结尾 SELECT country FROM dbo.Websites WHERE country LIKE 'a%' --a开头 SELECT country FROM dbo.Websites WHERE country LIKE '_a_' --三位并且中间是a SELECT country FROM dbo.Websites WHERE country LIKE '_a' --两位并且末尾是a SELECT country FROM dbo.Websites WHERE country LIKE 'a_' --两位并且a开头 --返回多个条件中符合的条目 SELECT * FROM dbo.Websites WHERE alexa IN ('1','0','100') --返回范围内的数据 SELECT * FROM dbo.Websites WHERE alexa BETWEEN 1 AND 26 --[]两边都包括 --列的别名(单个以及多个) SELECT name AS wName,CONCAT(url,'-',alexa,'-',country) AS allName FROM dbo.Websites --表的别名 SELECT * FROM dbo.Websites a,dbo.Zhaocl b WHERE a.alexa = b.gender
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