查询性能WHERE子句包含IN（子查询）

Question

SELECT Trade.TradeId, Trade.Type, Trade.Symbol, Trade.TradeDate, 
       SUM(TradeLine.Notional) / 1000 AS Expr1
FROM   Trade INNER JOIN
             TradeLine ON Trade.TradeId = TradeLine.TradeId
WHERE  (TradeLine.Id IN
                      (SELECT     PairOffId
                        FROM          TradeLine AS TradeLine_1
                        WHERE      (TradeDate <= '2011-05-11')
                        GROUP BY PairOffId
                        HAVING      (SUM(Notional) <> 0)))
GROUP BY Trade.TradeId, Trade.Type, Trade.Symbol, Trade.TradeDate
ORDER BY Trade.Type, Trade.TradeDate

当表开始增长时，我担心WHERE子句中IN的性能。有没有人对这种查询有更好的策略？子查询返回的记录数比TradeLine表中的记录数增长得慢得多。TradeLine表本身以每天10个的速度增长。

谢谢你。

编辑：我使用了将子查询从WHERE移到FROM的想法。我对有助于此新查询的所有答案投了赞成票。

   SELECT Trade.TradeId, Trade.Type, Trade.Symbol, Trade.TradeDate,   
          PairOff.Notional / 1000 AS Expr1
   FROM         Trade INNER JOIN
                  TradeLine ON Trade.TradeId = TradeLine.TradeId INNER JOIN
                      (SELECT     PairOffId, SUM(Notional) AS Notional
                        FROM          TradeLine AS TradeLine_1
                        WHERE      (TradeDate <= '2011-05-11')
                        GROUP BY PairOffId
                   HAVING (SUM(Notional) <> 0)) AS PairOff ON TradeLine.Id = PairOff.PairOffId
   ORDER BY Trade.Type, Trade.TradeDate

Answer 1

IN子句中的子查询不依赖于外部查询中的任何内容。您可以安全地将其移到FROM子句中；一个理智的查询计划生成器将自动执行此操作。

另外，必须调用EXPLAIN PLAN要在生产中使用的任何查询。这样做并查看DBMS对此查询计划的看法。