ORACLE知识范围内,你见过哪些因存在NULL值而使得调用或查询的(中间或最终)结果返回NULL或FALSE值的情况?
如:
1、SELECT * from test1A whereA.cl= A.c1
/*若c1中含空值,则返回结果并非A表中的所有记录*/
2、SELECT count(*) from dualA WHERE'a' NOT IN ('b',NULL)
/*结果为0*/
3、select translate('abc',NULL,'a') from dual
/*结果为NULL*/
SELECT count(*) from dualA WHERE'a' NOT IN ('b',NULL) 结果返回0
SELECT count(*) from dualA WHERE'a' NOT IN ('a','b',NULL) 结果也是0
SELECT count(*) from dualA WHERE'a' NOT IN ('a','b',NULL) 结果为1