一、SQL Server Select Top语句Select Top字句用于限制查询结果集中返回的行数或百分比由于存储在表中的行的顺序是不可逆的,因此Select Top语句始终与order by字句一起使用,结果集限于前n个有序行数。以下是带有select语句的Top字句的语法: 在此语法中, SELECT 语句可以包含其他子句,如: WHERE , JOIN , HAVING ...
一.SELECT的基本语法结构:SELECT [DISTINCT|ALL][TOP(<expression>)[PERCENT][WITH THIS]][[colmn_name[AS 列名]],[...]]|* FROM table_name [OUTER|LEFT|RIGHT|FULL|CROSS JOIN table1_name ON condition ] [... 结果集 子查询 嵌套 转载 ...
select top n * from tablename order by newid() 14、删除重复记录,请用查询分析器分析性能开销! 1)delete from tablename where id not in (select max(id) from tablename group by column1,column2,column3...) 2)select distinct * into temp from tablename; delete from tablename; insert into ...
DECLARE @qty INT SELECT @qty=qty FROM kucun WITH(UPDLOCK) WHERE [product]='牙膏' --阻塞 SELECT @qty --session 1提交之后才可以读,但是后面的update语句不会执行,这个时候更新丢失,使用try catch机制来捕获更新丢失 UPDATE kucun SET qty=@qty-1 WHERE [product]='牙膏' COMMIT TRAN 第二种: 如果使...
select top 1 classId from TestDataBase..Student where stuName='濮阳语儿' )); --表值 select * from (子查询) as 别名 select * from ( select stuName, case stuSex when 'f' then '女' else '男' end as stuSex, DATEDIFF(YEAR, stuBirthdate, GETDATE()) as stuAge from TestDataBase....
SELECT TOP 2 * FROM Score AS T WHERE T1.StudentNo = T.StudentNo ORDER BY T.ExamDate DESC ) AS T2 outer apply 类似(left outer join 当匹配不到的时候,右表返回空) OUTER APPLY 的意思是“外部应用”,与 CROSS APPLY 的原理一致,只是在匹配失败时,左表与右表也将合并为一条记录输出,不过右表的...
Select sum(字段名) from [表名] ; len 查找某文本字段的各个值长度: Select len (字段名) from [表名] ; avg 查找某字段的平均值: Select avg(字段名) from [表名] ; 根据指定的列对结果集进行排序的查找( 顺序、逆顺序): Select (字段名) from [表名] order by (字段名) ; Select (字段名)...
sqlserver没有明确的limit和skip方法,可以使用row_number函数和over一起实现分页查询。实例代码如下: SELECT TOP ([limit]) * from (select ROW_NUMBER() over( order by [CreatedDate] ) row_num,* FROM [GroupDb].[dbo].[Group_tb]) temptable where row_num>[skip] ...
SELECTage FROMperson ORDERBYageASC LIMIT 1 OFFSET 2 Microsoft SQL Server SELECTTOP3WITHTIES * FROMperson ORDERBYageASC 两个代码块都实现了相同的结果 - 从名为person的表中返回3个年龄最小的条目。但语法有了巨大的变化。当然,语法是主观的,所以我们不能给出任何建议; 选择对你来说更直观的东西。可以在...
1: 行转列子查询,获取一定数据集结果SELECT objid,action,count1 AS count FROM TMyAttention WHERE objidINSELECT TOP 10 objid FROM TMyAtten