【数据库】 SQL 常用语句

【数据库】 SQL 常用语句

1.批量导入

INSERT INTO Table2(field1,field2,...) SELECT value1,value2,... FROMTable1
要求目标表Table2必须存在

2.批量导入

SELECT vale1, value2 INTO Table2 FROM Table1
要求目标表Table2不存在，因为在插入时会自动创建表Table2，并将Table1中指定字段数据复制到Table2中

3.去重并保留一项

DELETE FROM  TableName WHERE ColName IN (select  ColName
  FROM TableName GROUP BY  ColName HAVING COUNT(ColName) > 1)
  AND id NOT in(  select  MAX(id)  FROM ColName GROUP BY  ProductId HAVING COUNT(ColName) > 1)

4.批量更新 

UPDATE t1 
SET Field1 = Field21, Field2 = Field22 
FROM Table2 t2       
WHERE ((t2.Field24 >= '') AND t1.fId = t4.fId);

5.分页

--max/top
SELECT TOP 50 * FROM pagetest
WHERE id>(SELECT MAX(id) FROM (SELECT TOP 9900 id FROM pagetest ORDER BY id)a)
ORDER BY id 
--row_number()
SELECT * FROM
(SELECT ROW_NUMBER()OVER(ORDER BY id)rownumber,* FROM pagetest)a
WHERE rownumber>=9901 and rownumber<=9952
-- OFFSET FETCH (需要sql2012以上)
SELECT * FROM    pagetest
ORDER BY id ASC 
OFFSET @pageIndex * @pageSize ROWS 
FETCH NEXT @pageSize ROWS ONLY 

6. 表同步 MERGE 

  MERGE into [MergeDemo] as m -- 目标表
  using Test as t -- 源表
  on m.[title]=t.[name] -- 匹配条件
  when matched then update set m.[num]=t.[age] -- 匹配成功
  when not matched then insert values(t.[name],t.[age]) -- 目标表与源表不一致
  when not matched by source then delete -- 源表与目标表不一致
  output $action as [action] -- 输出操作
  , inserted.[title] [ititle],inserted.[num] [inum]
  , deleted.[title] [dtitle],deleted.[num] [dnum];

7. GROUP 加 TOP（每个 GROUP 取出 TOP 数据）

Declare @currentIndex int   -- 游标
Declare @totalRows    int    -- 总的组数
Declare @time    nvarchar(20)     -- 第一个分组列
SET @currentIndex=1
  -- 按 第一个分组列 分组， 取出组名
  SELECT row_number()over(order by [time] asc) id,[time] INTO #temp1   
  FROM (SELECT DISTINCT(CONVERT(VARCHAR(10),create_time,120)) [time]  FROM tableName) a
  SELECT @totalRows=COUNT(1) FROM #temp1 -- 总的组数
WHILE @currentIndex<=@totalRows   -- 按 组名 循环
BEGIN   
  SELECT @time=[time] FROM #temp1 WHERE id=@currentIndex -- 取出当前组名
  -- 取出当前 组 拥有的数据， 再按照 第二分组列 分组 取 TOP
  SELECT TOP 20  colName 'Url', COUNT((colName)) 'Count',CONVERT(VARCHAR(10),create_time,120) 'Time',GETDATE()   
  FROM tableName   WHERE [time] =  @time   GROUP BY colName   ORDER BY COUNT((colName)) DESC
SET @currentIndex =@currentIndex+1
END