此查询查找K2的W_G是什么（例如：通过'E1'找到'L_E'）。然后找到K1是什么（例如：“ IS”由“ E1”找到）。然后根据K1，K2（由“ IS”和“ C01A”得出的“ 30”，“ 10”）找到什么K4，K5。
为了加快此查询的速度，是否需要修改此查询？
执行计划如下。
----------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
----------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | | 5 (0)| 00:00:01 |
| 1 | VIEW | | 1 | 13 | 2 (0)| 00:00:01 |
| 2 | TABLE ACCESS FULL | SYS_TEMP_0FD9D6617_CD798E | 1 | 26 | 2 (0)| 00:00:01 |
| 3 | TEMP TABLE TRANSFORMATION | | | | | |
| 4 | LOAD AS SELECT | SYS_TEMP_0FD9D6618_CD798E | | | | |
|* 5 | TABLE ACCESS FULL | C_W_B | 1 | 273 | 3 (0)| 00:00:01 |
| 6 | VIEW | | 1 | 13 | 2 (0)| 00:00:01 |
| 7 | TABLE ACCESS FULL | SYS_TEMP_0FD9D6617_CD798E | 1 | 26 | 2 (0)| 00:00:01 |
|* 8 | VIEW | | 1 | 39 | 2 (0)| 00:00:01 |
| 9 | TABLE ACCESS FULL | SYS_TEMP_0FD9D6618_CD798E | 1 | 273 | 2 (0)| 00:00:01 |
| 10 | SORT AGGREGATE | | 1 | 13 | | |
| 11 | VIEW | | 1 | 13 | 2 (0)| 00:00:01 |
| 12 | TABLE ACCESS FULL | SYS_TEMP_0FD9D6618_CD798E | 1 | 273 | 2 (0)| 00:00:01 |
| 13 | TEMP TABLE TRANSFORMATION | | | | | |
| 14 | LOAD AS SELECT | SYS_TEMP_0FD9D6617_CD798E | | | | |
|* 15 | TABLE ACCESS FULL | C_W_B | 1 | 78 | 3 (0)| 00:00:01 |
| 16 | FAST DUAL | | 1 | | 2 (0)| 00:00:01 |
----------------------------------------------------------------------------------------------------------
Statistics
----------------------------------------------------------
4 recursive calls
16 db block gets
30 consistent gets
2 physical reads
1156 redo size
682 bytes sent via SQL*Net to client
416 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
塔贝尔在下面
CREATE TABLE C_W_B (
HE VARCHAR2(22),
WE VARCHAR2(22),
G_D VARCHAR2(22),
W_G VARCHAR2(22),
W_V VARCHAR2(22),
K1 VARCHAR2(22),
K2 VARCHAR2(22),
K3 VARCHAR2(22),
K4 VARCHAR2(22),
K5 VARCHAR2(22),
K6 VARCHAR2(22),
K7 VARCHAR2(22),
K8 VARCHAR2(22),
K9 VARCHAR2(22),
K10 VARCHAR2(22),
K11 VARCHAR2(22),
K12 VARCHAR2(22),
K13 VARCHAR2(22),
K14 VARCHAR2(22),
K22 VARCHAR2(22),
K16 VARCHAR2(22)
);
数据如下
INSERT INTO C_W_B(HE,WE,G_D,W_G,W_V,K1,K3,K4,K6) VALUES
('C6','61','R3','L_C_F','1','IS','C01A','30','10');
INSERT INTO C_W_B(HE,WE,G_D,W_G,K1,K2) VALUES
('C6','61','R3','L_E','IS','E1');
查询如下
WITH G_S AS (
SELECT /*+FIRST_ROWS(1)*/
A.W_G, A.K1
FROM C_W_B A
WHERE 1=1
AND A.HE = 'C6'AND A.WE = '61' AND A.G_D ='R3' AND A.K2='E1'
)
SELECT CASE
WHEN (SELECT A.W_G FROM G_S A)='L_E'
THEN (
WITH SEO AS (
SELECT A.K1 FROM G_S A
),
SE AS (SELECT *
FROM C_W_B B
WHERE B.W_G = 'L_C_F'
AND B.HE = 'C6'
AND B.WE = '61'
AND B.G_D ='R3'
AND B.K1 = (SELECT K1 FROM SEO)
AND B.K3 LIKE 'C01A'
)
SELECT (L_T /QT*1000)
FROM ( SELECT NVL(TO_NUMBER(K4),0) AS L_T,
NVL(TO_NUMBER(K6),0) AS QT
FROM SE
WHERE W_V IN (SELECT TO_CHAR(MAX(TO_NUMBER(W_V))) FROM SE )
)
)
WHEN 1=2
THEN TO_NUMBER(0)
ELSE TO_NUMBER(0)
END
FROM DUAL;
您的查询可以简化，并且可以提供如下性能：
SELECT CASE
WHEN W_G ='L_E'
AND K6 IS NOT NULL -- ADDED K6 IS NOT NULL CONDITION TO AVOID NUMBER DIVIDE BY 0 ERROR
THEN NVL(K4,0) / (K6*1000)
ELSE 0
END
FROM (SELECT A.W_G, B.K6, B.K4,
ROW_NUMBER()
OVER (ORDER BY TO_NUMBER(W_V) DESC NULLS LAST) AS RN
FROM C_W_B A JOIN C_W_B S ON (A.K1=S.K1)
WHERE A.HE = 'C6'
AND A.WE = '61'
AND A.G_D ='R3'
AND A.K2='E1'
AND S.W_G = 'L_C_F'
AND S.HE = 'C6'
AND S.WE = '61'
AND S.G_D ='R3'
AND S.K3 LIKE 'C01A')
WHERE RN = 1;
干杯！