exists改写SQL，使其走正确的执行计划

数据库环境：SQL SERVER 2005

　　今天看到一条SQL，写得不是很复杂，返回7000多条数据，却执行了15s。SQL文本及各表的数据量如下：

SELECT  acinv_07.id_item ,
        SUM(acinv_07.dec_endqty) dec_endqty
FROM    acinv_07
WHERE   acinv_07.fiscal_year * 100 + acinv_07.fiscal_period = ( SELECT DISTINCT
                                                              ctlm1101.fiscal_year
                                                              * 100
                                                              + ctlm1101.fiscal_period
                                                              FROM
                                                              ctlm1101
                                                              WHERE
                                                              flag_curr = 'Y'
                                                              AND id_oprcode = 'acinv'
                                                              AND acinv_07.id_wh = ctlm1101.id_table
                                                              )
GROUP BY acinv_07.id_item
----------------------------------------
SELECT  COUNT(*)
FROM    ctlm1101
WHERE   flag_curr = 'Y'
        AND id_oprcode = 'acinv'--26
        
SELECT  COUNT(*)
FROM    acinv_07--1347176

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