postgresql与Oracle：空字符串与null

空字符串与null"/>

postgresql与Oracle：空字符串与null

空字符串：两个单引号，中间无空格等任何内容在postgresql中，空字符串与null是不同的；而oracle中，空字符串与null等同。测试如下：postgresql中：
postgres=# insert into testnull values(1,'feikong');
INSERT 0 1
postgres=# insert into testnull values(2,null);
INSERT 0 1
postgres=# insert into testnull values(3,'');
INSERT 0 1
postgres=#  select * from testnull;id |  name   
----+---------1 | feikong2 |3 |
(3 rows)postgres=# select * from testnull where name is null;     ---只有2为nullid | name
----+------2 |
(1 row)postgres=# select * from testnull where name is  not null;id |  name   
----+---------1 | feikong3 |
(2 rows)Oracle中：
SQL> insert into testnull values(1,'feikong');1 row insertedSQL> insert into testnull values(2,null);1 row insertedSQL> insert into testnull values(3,'');1 row insertedSQL> commit;Commit completeSQL> select * from testnull;ID NAME
---------- ----------1 feikong23SQL> select * from testnull where name is null;   --2,3为nullID NAME
---------- ----------23SQL> select * from testnull where name is  not null;ID NAME
---------- ----------1 feikong