select CONNECTION from wanglong.userlike t WHERE CONNECTION is null;
或者 select CONNECTION from wanglong.userlike t WHERE CONNECTION = null;
if you want to judge a value whether is null in oracle,you must use "is null" or "is not null"
select len(CONNECTION) A from wanglong.userlike t WHERE CONNECTION is null;
呵呵,大学里老师都说了n次了,'' <> null
oracle 与sql server不同 sql server: where col_name='' and col_name is null oracle where col_name is null
to 楼上.. 在oracle中好象''就和null等效哦,不信你试试,所以我说oracle非常变态
在ORACLE中,''是不存在的,基本上都是以NULL存在,但程序中,SQL语句中却可以写'',但是:'' 觉不等于null. oracle提供一个函数:nvl来处理空值,你的语句可以这样写: select CONNECTION from wanglong.userlike t WHERE nvl(CONNECTION,'1') ='1' ; select CONNECTION from wanglong.userlike t WHERE nvl(CONNECTION,'0') ='0' ; 或这样写: select CONNECTION from wanglong.userlike t WHERE CONNECTION is null; 这样写也可以,但我没有试:(一般不这样写,因为ORACLE中''和null经常混搅不清) select CONNECTION from wanglong.userlike t WHERE nvl(CONNECTION,'') ='' ;
select CONNECTION from wanglong.userlike t WHERE CONNECTION is null
select CONNECTION from wanglong.userlike t WHERE CONNECTION is null;
select CONNECTION from wanglong.userlike t WHERE CONNECTION = null;
or "is not null"
sql server:
where col_name='' and col_name is null
oracle
where col_name is null
在oracle中好象''就和null等效哦,不信你试试,所以我说oracle非常变态
oracle提供一个函数:nvl来处理空值,你的语句可以这样写:
select CONNECTION from wanglong.userlike t WHERE nvl(CONNECTION,'1') ='1' ;
select CONNECTION from wanglong.userlike t WHERE nvl(CONNECTION,'0') ='0' ;
或这样写:
select CONNECTION from wanglong.userlike t WHERE CONNECTION is null;
这样写也可以,但我没有试:(一般不这样写,因为ORACLE中''和null经常混搅不清)
select CONNECTION from wanglong.userlike t WHERE nvl(CONNECTION,'') ='' ;