[Index]Null值和索引的问题
[Index]Null值和索引的问题 Index是不存储NULL值的,所以如果你有NULL的条件在SQL中,那么相关的索引是用不到的。 CREATE TABLE PTIAN1 AS (SELECT * FROM DBA_OBJECTS); www.2cto.com CREATE INDEX PTIAN_INDEX ON PTIAN1(DATA_OBJECT_ID); EXEC DBMS_STATS
[Index]Null值和索引的问题
Index是不存储NULL值的,所以如果你有NULL的条件在SQL中,那么相关的索引是用不到的。
CREATE TABLE PTIAN1 AS (SELECT * FROM DBA_OBJECTS); www.2cto.com
CREATE INDEX PTIAN_INDEX ON PTIAN1(DATA_OBJECT_ID);
EXEC DBMS_STATS.GATHER_TABLE_STATS('APPS','PTIAN1', CASCADE=>TRUE );
SELECT * FROM PTIAN1 WHERE DATA_OBJECT_ID = 11;
SELECT * FROM PTIAN1 WHERE DATA_OBJECT_ID IS NULL;
解决方法
创建Function-Based Index
CREATE INDEX PTIAN_FUNC_INDEX ON PTIAN1 (NVL(DATA_OBJECT_ID,-1));
EXEC DBMS_STATS.GATHER_TABLE_STATS('APPS','PTIAN1', CASCADE=>TRUE );
SELECT OBJECT_NAME FROM PTIAN1 WHERE NVL(DATA_OBJECT_ID,-1) = -1;
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