END AS Growth_MOM_RAT
FROM dbo.DiskCapacityHistory M ,
dbo.DiskCapacityHistory N
WHERE CAST(CAST(M.Date_CD AS CHAR(8)) AS DATE) = DATEADD(MONTH, 1,
CAST(CAST(N.Date_CD AS CHAR(8)) AS DATE))
AND M.DataBaseID = N.DataBaseID
AND M.FileID = N.FileID
AND M.Date_CD = CAST(REPLACE(CONVERT(VARCHAR(10), GETDATE()
– 1, 120), ‘-‘, ”) AS INT)
UPDATE dbo.DiskCapacityHistory
SET Growth_MOM_RAT = M.Growth_MOM_RAT
FROM #DiskCapacityHistory M
WHERE dbo.DiskCapacityHistory.DATE_CD = M.DATE_CD
AND dbo.DiskCapacityHistory.DataBaseID = M.DataBaseID
AND dbo.DiskCapacityHistory.FileID = M.FileID ;
2: 幸好SQL 2008还把ORACLE的MERGE的功能给模仿了过来，但是T-SQL缺少ORACLE数据库强大的分析函数LAG，如果有这个，我计算环比，同比就非常方便了，一个SQL就搞定了，下面是个例子，本想把ORACLE的SQL也做个例子展现，但是又要建表、造数，折腾起来比较麻烦。
MERGE INTO DM.TM_WGGBO_IDCTOBUSVOLDTL_DAY DM
USING (
SELECT *
FROM (
SELECT DATE_CD,
CITY_ID,
IDC_NODE,
