挑战SQL极限——SQL优化(大数据量)
最近在做数据分析,遇到了SQL查询优化的问题,想请教大家:
【场景】
(1)三张表:Budget(2.5万条记录) LinkTable(15万条记录) Sales(30万条记录)
(2)用SQL语句对着三张表进行一个关联汇总查询时,竟然需要35-40秒钟
(3)对三张表的关联字段和汇总字段建立索引后,查询仍然需要10秒钟
【目的】
希望能将查询时间控制在1秒钟内,也就是希望通过对现有SQL语句的优化(或其它办法)将现有的查询效率提高10倍。
【SQL查询语句】
SELECT [Year],
MIN((CASE WHEN (Year = 2009 OR Year = 2009-1) THEN Sales / EUR END)) AS [Sales],
Sum(Budget_EUR * _Projected) AS [Projected]
FROM (SELECT [A].[Year], [A].[Sales], [A].[EUR], [Budget].[Budget_EUR], [Budget].[_Projected],
[A].[SalesKey], [A].[BudgetKey]
FROM ((SELECT [LinkTable].[Year], [Sales].[Sales], [Sales].[EUR], [LinkTable].[SalesKey],
[LinkTable].[BudgetKey]
FROM ([LinkTable] LEFT JOIN [Sales] ON [LinkTable].[SalesKey] = [Sales].[SalesKey]))
AS A LEFT JOIN [Budget] ON [A].[BudgetKey] = [Budget].[BudgetKey]))
GROUP BY [Year]
请大家检查一下以上SQL语句有哪些地方可以优化,谢谢。
【数据库结构】
CREATE TABLE [Budget] ([BudgetKey] VARCHAR(21) NULL, [_Projected] INTEGER, [Budget_SEK] INTEGER, [Budget_GBP] INTEGER, [Budget_JPY] INTEGER, [Budget_EUR] INTEGER, [Budget_USD] REAL, [Projected_SEK] INTEGER, [Projected_GBP] INTEGER, [Projected_JPY] INTEGER, [Projected_EUR] INTEGER);
CREATE TABLE [LinkTable] ([SalesKey] VARCHAR(21) NULL, [Year] INTEGER, [Month] VARCHAR(23) NULL, [MonthYear] VARCHAR(25) NULL, [_History] INTEGER, [Quarter] VARCHAR(27) NULL, [QtrYear] VARCHAR(29) NULL, [Week] INTEGER, [Weekstart] VARCHAR(31) NULL, [Weekend] VARCHAR(33) NULL, [Customer Number] VARCHAR(35) NULL, [BudgetKey] VARCHAR(37) NULL);
CREATE TABLE [Sales] ([Date] VARCHAR(12) NULL, [Address Number] VARCHAR(14) NULL, [Sales Rep Number] INTEGER, [Item Number] INTEGER, [Invoice Date] VARCHAR(16) NULL, [Promised Delivery Date] VARCHAR(18) NULL, [Invoice Number] INTEGER, [Order Number] INTEGER, [Item Desc] VARCHAR(39) NULL, [Sales Qty] REAL, [Open Qty] INTEGER, [OpenOrder] REAL, [GrossSales] REAL, [Sales] REAL, [BackOrder] REAL, [Cost] REAL, [Margin] REAL, [SEK] VARCHAR(41) NULL, [GBP] VARCHAR(43) NULL, [AUD] VARCHAR(45) NULL, [JPY] VARCHAR(47) NULL, [EUR] VARCHAR(49) NULL, [USD] INTEGER, [SalesKey] VARCHAR(51) NULL, [# of Days Late] INTEGER, [# of Days to Ship] INTEGER);
请大家多多指教 !
很多年没有来这个论坛了,不知以前SQLServer版的大佬们还在不在?