1. 关于如何获取1对多数据中最大条数据的写法

　　　　例子: 

　　　　　　LEFT JOIN ( SELECT *

FROM table AS n1

WHERE 

n1.ID IN

(

　　SELECT MAX(id) FROM table AS n2 GROUP BY n2.House_ID

)

) ne ON ne.House_ID = C.Null1

　　　　通过两层的嵌套，group by 分组获取最大值，然后通过 in 方法来查询其他信息

 

2、查询是否有断的ID

 

SELECT * FROM 

dbo.table  AS a

WHERE a.ID+1

NOT IN

(

SELECT b.ID FROM dbo.table  AS b

) 

 

3、上下两条数据合成一条带时间的数据

 

SELECT DISTINCT ISNULL(fybl2.ZYRQ,'1900-01-01') AS ZYRQ1,fybl1.* FROM T_FYBL AS fybl1

LEFT JOIN dbo.T_FYBL AS fybl2 ON fybl1.YJ_ID=fybl2.YJ_ID AND fybl1.ID>fybl2.ID AND fybl1.JSM=fybl2.JSM

 

4、空值，null值，0值，0.0值等筛选处理

or ISNULL(AC.CommissionAmount,'0') NOT IN('','0','0.00')

 

5、获取系统数据字典:

--表描述

SELECT tbs.name 表名,ds.value 描述

FROM sys.extended_properties ds

LEFT JOIN sysobjects tbs ON ds.major_id=tbs.id

WHERE ds.minor_id=0 AND tbs.type='U'

--快速查看表结构

SELECT CASE WHEN col.colorder = 1 THEN obj.name

ELSE ''

END AS 表名,

col.colorder AS 序号 ,

col.name AS 列名 ,

ISNULL(ep.[value], '') AS 列说明 ,

t.name AS 数据类型 ,

col.length AS 长度 ,

ISNULL(COLUMNPROPERTY(col.id, col.name, 'Scale'), 0) AS 小数位数 ,

CASE WHEN COLUMNPROPERTY(col.id, col.name, 'IsIdentity') = 1 THEN '√'

ELSE ''

END AS 标识 ,

CASE WHEN EXISTS ( SELECT 1

FROM dbo.sysindexes si

INNER JOIN dbo.sysindexkeys sik ON si.id = sik.id

AND si.indid = sik.indid

INNER JOIN dbo.syscolumns sc ON sc.id = sik.id

AND sc.colid = sik.colid

INNER JOIN dbo.sysobjects so ON so.name = si.name

AND so.xtype = 'PK'

WHERE sc.id = col.id

AND sc.colid = col.colid ) THEN '√'

ELSE ''

END AS 主键 ,

CASE WHEN col.isnullable = 1 THEN '√'

ELSE ''

END AS 允许空 ,

ISNULL(comm.text, '') AS 默认值

FROM dbo.syscolumns col

LEFT JOIN dbo.systypes t ON col.xtype = t.xusertype

inner JOIN dbo.sysobjects obj ON col.id = obj.id

AND obj.xtype = 'U'

AND obj.status >= 0

LEFT JOIN dbo.syscomments comm ON col.cdefault = comm.id

LEFT JOIN sys.extended_properties ep ON col.id = ep.major_id

AND col.colid = ep.minor_id

AND ep.name = 'MS_Description'

LEFT JOIN sys.extended_properties epTwo ON obj.id = epTwo.major_id

AND epTwo.minor_id = 0

AND epTwo.name = 'MS_Description'

ORDER BY col.colorder ;