操作系統(tǒng)：Windows XP
數(shù)據(jù)庫版本：SQL Server 2005
今天遇到一個(gè)SQL，過濾條件是自動(dòng)生成的，因此，沒法通過調(diào)整SQL的謂詞達(dá)到優(yōu)化的目的，只能去找SQL中的“大表”。有一個(gè)視圖返回的結(jié)果集比較大，如果能調(diào)整的話，也只能調(diào)整該視圖了。
看了一下該視圖的結(jié)構(gòu)，里面還套用了另一層視圖，直接看最里層視圖的查詢SQL。
SELECT a.dfeesum_no ,
a.opr_amt - ISNULL(b.dec_pay, 0) - ISNULL(b.dec_corrpay, 0)
- ISNULL(b.dec_deduamt, 0) dec_amt ,
a.dec_camt - ISNULL(b.dec_pay, 0) - a.dec_comprate
* ISNULL(b.dec_deduamt, 0) dec_compamt ,
a.dec_ramt - ISNULL(b.dec_corrpay, 0) - ( a.dec_comprate - 1 )
* ISNULL(b.dec_deduamt, 0) dec_corramt ,
a.dec_qty - ISNULL(b.dec_qty, 0) - ISNULL(b.dec_deduqty, 0) opr_qty ,
ISNULL(b.dec_pay, 0) dec_pay ,
ISNULL(b.dec_corrpay, 0) dec_corrpay ,
ISNULL(b.dec_deduqty, 0) dec_deduqty ,
ISNULL(b.dec_deduamt, 0) dec_deduamt ,
ISNULL(b.dec_qty, 0) dec_qty
FROM ctlm8686 a
LEFT JOIN ( SELECT dfeesum_no ,
SUM(dec_ramt) dec_pay ,
SUM(dec_corramt) dec_corrpay ,
SUM(dec_qty) dec_qty ,
SUM(CASE WHEN flag_dedu = '1' THEN dec_deduamt
ELSE 0
END) dec_deduamt ,
SUM(CASE WHEN flag_dedu = '1' THEN dec_deduqty
ELSE 0
END) dec_deduqty
FROM dfeepay_03
GROUP BY dfeesum_no
) b ON a.dfeesum_no = b.dfeesum_no
UNION ALL
SELECT a.dfeesum_no ,
a.dec_amt - ISNULL(b.dec_pay, 0) - ISNULL(b.dec_corrpay, 0)
- ISNULL(b.dec_deduamt, 0) dec_amt ,
a.dec_compamt - ISNULL(b.dec_pay, 0) - a.dec_comprate
* ISNULL(b.dec_deduamt, 0) dec_compamt ,
a.dec_corramt - ISNULL(b.dec_corrpay, 0) - ( a.dec_comprate - 1 )
* ISNULL(b.dec_deduamt, 0) dec_corramt ,
a.opr_qty - ISNULL(b.dec_qty, 0) - ISNULL(b.dec_deduqty, 0) opr_qty ,
ISNULL(b.dec_pay, 0) dec_pay ,
ISNULL(b.dec_corrpay, 0) dec_corrpay ,
ISNULL(b.dec_deduqty, 0) dec_deduqty ,
ISNULL(b.dec_deduamt, 0) dec_deduamt ,
ISNULL(b.dec_qty, 0) dec_qty
FROM dfeeapp_03 a
LEFT JOIN ( SELECT dfeesum_no ,
SUM(dec_ramt) dec_pay ,
SUM(dec_corramt) dec_corrpay ,
SUM(dec_qty) dec_qty ,
SUM(CASE WHEN flag_dedu = '1' THEN dec_deduamt
ELSE 0
END) dec_deduamt ,
SUM(CASE WHEN flag_dedu = '1' THEN dec_deduqty
ELSE 0
END) dec_deduqty
FROM dfeepay_03
GROUP BY dfeesum_no
) b ON a.dfeesum_no = b.dfeesum_no
返回結(jié)果集有1433891行，其中
SELECT COUNT(*) FROM dfeepay_03 --1103914
SELECT COUNT(*) FROM ctlm8686 --1131586
SELECT COUNT(*) FROM dfeeapp_03--302305
上述SQL腳本中，子查詢是相同的，即對(duì)子查詢進(jìn)行了兩次掃描，可以考慮先讓dfeeapp_03和ctlm8686union all，再left join?dfeepay_03 。同時(shí)，對(duì)于子查詢，先讓dfeepay_03 表先查詢出flag_dedu = '1'的數(shù)據(jù)，就不用再進(jìn)行case when判斷了。
改寫后的SQL如下
SELECT a.dfeesum_no ,
a.opr_amt - ISNULL(b.dec_pay, 0) - ISNULL(b.dec_corrpay, 0)
- ISNULL(b.dec_deduamt, 0) dec_amt ,
a.dec_camt - ISNULL(b.dec_pay, 0) - a.dec_comprate
* ISNULL(b.dec_deduamt, 0) dec_compamt ,
a.dec_ramt - ISNULL(b.dec_corrpay, 0) - ( a.dec_comprate - 1 )
* ISNULL(b.dec_deduamt, 0) dec_corramt ,
a.dec_qty - ISNULL(b.dec_qty, 0) - ISNULL(b.dec_deduqty, 0) opr_qty ,
ISNULL(b.dec_pay, 0) dec_pay ,
ISNULL(b.dec_corrpay, 0) dec_corrpay ,
ISNULL(b.dec_deduqty, 0) dec_deduqty ,
ISNULL(b.dec_deduamt, 0) dec_deduamt ,
ISNULL(b.dec_qty, 0) dec_qty
FROM ( SELECT a.dfeesum_no ,
a.opr_amt ,
a.dec_camt ,
a.dec_comprate ,
a.dec_ramt ,
a.dec_qty
FROM ctlm8686 a
UNION ALL
SELECT a.dfeesum_no ,
a.dec_amt ,
a.dec_compamt ,
a.dec_comprate ,
a.dec_corramt ,
a.opr_qty
FROM dfeeapp_03 a
) a
LEFT JOIN ( SELECT dfeesum_no ,
SUM(dec_ramt) dec_pay ,
SUM(dec_corramt) dec_corrpay ,
SUM(dec_qty) dec_qty ,
SUM(dec_deduamt) dec_deduamt,
SUM(dec_deduqty) dec_deduqty
FROM dfeepay_03
WHERE flag_dedu = '1'
GROUP BY dfeesum_no
) b ON a.dfeesum_no = b.dfeesum_no
跑這個(gè)視圖的查詢語句，從原來的一分半鐘降到一分鐘，對(duì)于整個(gè)SQL而言，則從原來跑幾分鐘的直接10S出結(jié)果。
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