SELECT TOP(10) PERCENT * FROM T1 ORDER BY ID 在按照百分比来选取记录时,如果总行数*百分比的结果为小数,会向上取整然 当ORDER BY 指定的排序列值不唯一时,TOP的得到的结果集会不固定,比如对UserID排序后取TOP 1,满足最大或最小值的记录有多行,SQL Server可能返回其中任意一行,因此记录不固定。如果希望返回...
insert@aselect'a1','b1','c1','d1/da' unionallselect'a2','b2','c2','d22/da/da22' unionallselect'a3','b3','c3','d3' declare@ttable( idintidentity(1,1),eint) insert@tselecttop5001fromsyscolumns selecta,b,c,substring(d+'/',id,charindex('/',d+'/',id+1)-id)d from@aa...
SELECT TOP(5) orderid, orderdate, custid, empid FROM Sales.Orders ORDER BY orderdate DESC, orderid DESC; 1. 2. 3. 或者使用WITH TIES作为关联行,来实现tiebreaker SELECT TOP(5) WITH TIES orderid, orderdate, custid, empid FROM Sales.Orders ORDER BY orderdate DESC, orderid DESC; 1. 2....
一、逻辑查询处理的各个阶段(5)SELECT DISTINCT TOP() (1)FROM JOIN ON (2)WHERE (3)GROUP BY (4)HAVING (6)ORDER BY 上边语句是一个普通格式的查询语句,基本包含了所有的查询条件和关键字。你可能会发现前边的序号并不是按顺序来的,被你说对了,这是SQL与其他编程语言不同的最明显特征,就是它的执行...
( Select Substring(@MyString, A.Position, @Length - A.Number + 1) As MySubstring , @Length - A.Number + 1 As StringLen ) B ) Select Top 1 with Ties MySubstring As longest_repeating_String From CTE Where MyCount > 1 and PositionGap >= 0 Order by StringLen DescExplana...
综上所述,TSQL是一种强大的语言,可以用于更新数据表中的数据,包括使用INSERT INTO SELECT FROM语句和UPDATE语句来更新数据表中的数据。 相关搜索: insert into / select from ordered Insert into table with多个select,包括select distinct from from insert into select from 锁表 ...
SELECT TOP1CAST( [Extent1].[REG_CODE] ASint) +1FROM [dbo].[Notifications] [Extent1]WHERENOT([Extent1].[REG_CODE] LIKE N'%~[a-z]%'ESCAPE N'~')AND(1= (ISNUMERIC([Extent1].[REG_CODE]))) AND NOTEXISTS(SELECT * FROM [dbo].[Notifications] t2 WHERE CAST( t2.REG_CODE ASint)...
SELECT top 10 spid AS 'td','', case [blocking_spid] when 0 then '' else [blocking_spid] end AS 'td','', [Duration] AS 'td','', [database_name] AS 'td','', [open_tran_count] AS 'td','', [login_name] AS 'td','', ...
DECLARE @tag VARCHAR(MAX) DECLARE @TagID as INT; DECLARE @ID as INT; DECLARE tag_cursor CURSOR FOR SELECT tagname FROM #temptag FOR READ ONLY OPEN tag_cursor FETCH NEXT FROM tag_cursor INTO @tag WHILE @@FETCH_STATUS = 0 BEGIN IF EXISTS (SELECT TOP 1 * FROM Tag WHERE TagName=@tag...
insert into t1(c1,c2) select 100,'test' select * from t1 where c2='test' 查詢一筆資料卻使用資料表掃描運算子,主要是因為該欄位 (c2) 沒有建立索引所造成,但由於資料庫有開啟自動建立統計值選項,該選項可讓查詢優化程式估計基數。 SQL Server 自動建立統計值。