大多数情况下，oracle数据库内置的查询优化策略还是很成功的，但偶尔也有犯2的时候，即使有索引，也会做全表扫描，可以参考以下语句的写法，强制让select语句使用索引1 CREATE OR REPLACE VIEW V_RES_CBA AS
2 SELECT /*+INDEX(SEG IDX_T_RES_ALLOSEG_ALLOID)*/
3 ALLO.ALLOID AS RESID,
4 NULL AS AWB,
5 ALLO.ALLOTMENT AS ALLO_ID,
6 DAYS.FDATE + NVL(SEG.DAYSDISP, 0) AS FDATE,
7 ALLO.SPECULD AS SPECULD
8 FROM T_RES_ALLO ALLO, T_RES_ALLOSEG SEG, V_FDATE DAYS
9 WHERE ALLO.ALLOID = SEG.ALLOID
10 AND ((ALLO.ALLOIND = 'A' AND ALLO.ALLO_DATE = DAYS.FDATE) OR
11 (ALLO.ALLOIND = 'S' AND
12 NVL(ALLO.SDATE, ALLO.ALLO_DATE) = DAYS.FDATE))
13 UNION
14 SELECT /*+INDEX(SEG IDX_T_RES_ALLOSEG_ALLOID)*/
15 ALLO.ALLOID AS RESID,
16 NULL AS AWB,
17 ALLO.ALLOTMENT AS ALLO_ID,
18 DAYS.FDATE + NVL(SEG.DAYSDISP, 0) AS FDATE,
19 ALLO.SPECULD AS SPECULD
20 FROM T_RES_ALLO ALLO, T_RES_ALLOSEG SEG, V_FDATE DAYS
21 WHERE ALLO.ALLOID = SEG.ALLOID
22 AND ALLO.ALLO_DATE IS NULL
23 AND ALLO.ALLOIND = 'A'
24 AND (DAYS.FDATE >= ALLO.SDATE AND DAYS.FDATE <= ALLO.EDATE AND
25 INSTR(ALLO.WEEKDAY, DAYS.WEEKDAY) > 0)
26 AND NOT EXISTS (SELECT subQuery.ALLOID
27 from T_RES_ALLO subQuery
28 where subQuery.ALLO_DATE = DAYS.FDATE
29 and subQuery.ALLOTMENT = ALLO.ALLOTMENT)
30 ;
要点：
1、/*+INDEX(SEG IDX_T_RES_ALLOSEG_ALLOID)*/ 这里的/*...*/中间不要有空格
2、表名要用别名，即：以上面的sql语句为例，要使用SEG，而不是T_RES_ALLOSEG