将游标修改为建表来提高效率
题记：
最近一个同事说一个更新语句很慢求助与我，我看了下，这类语句的优化具有典型的代表性，于是记录下来和大家共享下。
原sql语句：
DECLARE
V_PARTYNO VARCHAR2(20);
V_APP_MP VARCHAR2(20);
V_INTIME DATE;
V_CNT INT;
BEGIN
FOR CUR IN (SELECT APPLICATION_NO FROM FRAUD_SCORE) LOOP
SELECT MAX(PARTY_NO),
MAX(MOBILE_PHONE_NO),
MAX(IMPORT_CPPCDM_TIME)
INTO V_PARTYNO,
V_APP_MP,
V_INTIME
FROM RISKREPT.RKO_CDM_PROCESS
WHERE APPLICATION_NO = CUR.APPLICATION_NO;
SELECT COUNT(1)
INTO V_CNT
FROM RISKREPT.RKO_CDM_PROCESS
WHERE PARTY_NO = V_PARTYNO
AND MONTHS_BETWEEN(V_INTIME,
IMPORT_CPPCDM_TIME) <= 12;
UPDATE FRAUD_SCORE
SET APP_LOANCARD_NUM = V_CNT
WHERE APPLICATION_NO = CUR.APPLICATION_NO;
COMMIT;
END LOOP;
INSERT INTO FRAUD_SCORE_LOG
(VAR_NAME,
FINISH_TIME,
SEQ_NO)
VALUES
('APP_LOANCARD_NUM',
SYSDATE,
'8');
END P_APP_LOANCARD_NUM;
看下数据量：
分析：表FRAUD_SCORE 大约有5147929 行数据，采用这种方式大约需要24小时，所以优化。。。。。。
这个块中表RISKREPT.RKO_CDM_PROCESS有多次扫描，该表也是400W的数据量，所以从这里下手优化，一般来说，建表的方式比游标要快，所以，提供三种优化方式：
---------------优化后的三种办法：
-------------------------------- 第一种办法 （推荐）----- 尽量将语句简单化
--------- 如果是存过中就用truncate + append + nologging 完成
------------ 我开了并行，大约10分钟，不开并行的话2个小时肯定跑完了
----------这种方式表建立完成后最好把表的并行模式修改为1
Create Table MHQ_TMP_A nologging parallel 20 As
SELECT A.ROWID ROWIDS,
B.APPLICATION_NO,
MAX(PARTY_NO) PARTY_NO,
MAX(MOBILE_PHONE_NO) MOBILE_PHONE_NO,
MAX(IMPORT_CPPCDM_TIME) IMPORT_CPPCDM_TIME
FROM RISKPUBFLN.FRAUD_SCORE A,
RISKREPT.RKO_CDM_PROCESS B
WHERE B.APPLICATION_NO = A.APPLICATION_NO
GROUP BY A.ROWID,
B.APPLICATION_NO ;
Create Table MHQ_TMP_B nologging parallel 20 As
SELECT A.ROWIDS,
COUNT(1) COUNTS
FROM MHQ_TMP_A A,
RISKREPT.RKO_CDM_PROCESS B
WHERE A.PARTY_NO = B.PARTY_NO
AND MONTHS_BETWEEN(A.IMPORT_CPPCDM_TIME,
B.IMPORT_CPPCDM_TIME) <= 12
GROUP BY A.ROWIDS;
---select count(1) from MHQ_TMP_B;
MERGE INTO RISKPUBFLN.FRAUD_SCORE A
USING MHQ_TMP_B B
ON (B.ROWIDS=A.ROWID)
WHEN MATCHED THEN
UPDATE SET A.APP_LOANCARD_NUM = B.COUNTS;
COMMIT;
-------------------------------- 第二种办法 （语句复杂，解析慢点，不太推荐）
MERGE INTO RISKPUBFLN.FRAUD_SCORE T
USING (SELECT BB.APPLICATION_NO,
COUNT(1) COUNTS
FROM (SELECT B.APPLICATION_NO,
MAX(PARTY_NO) PARTY_NO,
MAX(IMPORT_CPPCDM_TIME) IMPORT_CPPCDM_TIME
FROM RISKPUBFLN.FRAUD_SCORE A,
RISKREPT.RKO_CDM_PROCESS B
WHERE B.APPLICATION_NO = A.APPLICATION_NO
GROUP BY B.APPLICATION_NO) AA,
RISKREPT.RKO_CDM_PROCESS BB
WHERE BB.PARTY_NO = AA.PARTY_NO
AND MONTHS_BETWEEN(AA.IMPORT_CPPCDM_TIME,
BB.IMPORT_CPPCDM_TIME) <= 12
GROUP BY BB.APPLICATION_NO) TT
ON (T.APPLICATION_NO = TT.APPLICATION_NO)
WHEN MATCHED THEN
UPDATE SET T.APP_LOANCARD_NUM = TT. COUNTS
;
COMMIT;
-------------------------------- 第三 种办法 （游标for循环）
---------------- 尽量减少loop中的循环处理逻辑，也就是减少大表扫描次数
DECLARE
V_PARTYNO VARCHAR2(20);
V_APP_MP VARCHAR2(20);
V_INTIME DATE;
V_CNT INT;
V_COUNTS NUMBER;
BEGIN
FOR CUR IN ( SELECT A.ROWID ROWIDS,
B.APPLICATION_NO,
MAX(PARTY_NO) V_PARTYNO,
MAX(MOBILE_PHONE_NO) V_APP_MP,
MAX(IMPORT_CPPCDM_TIME) V_INTIME
FROM RISKPUBFLN.FRAUD_SCORE A,
RISKREPT.RKO_CDM_PROCESS B
WHERE B.APPLICATION_NO = A.APPLICATION_NO
group by A.ROWID ,B.APPLICATION_NO
order by a.rowid
) LOOP
SELECT COUNT(1)
INTO V_CNT
FROM RISKREPT.RKO_CDM_PROCESS
WHERE PARTY_NO = CUR.V_PARTYNO
AND MONTHS_BETWEEN(CUR.V_INTIME,
IMPORT_CPPCDM_TIME) <= 12;
UPDATE RISKPUBFLN.FRAUD_SCORE T
SET APP_LOANCARD_NUM = V_CNT
WHERE T.ROWID = CUR.ROWIDS;
V_NUM := V_NUM + 1;
IF MOD(V_NUM,
20000) = 0 THEN
COMMIT;
END IF;
END LOOP;
COMMIT;
INSERT INTO RISKPUBFLN.FRAUD_SCORE_LOG
(VAR_NAME,
FINISH_TIME,
SEQ_NO)
VALUES
('APP_LOANCARD_NUM',
SYSDATE,
'8');
END P_APP_LOANCARD_NUM;