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 1postgres=# insert into testnull values(2,null);INSERT 0 1postgres=# insert into testnull values(3,'');INSERT 0 1postgres=#  select * from testnull; id |  name   ----+---------  1 | feikong  2 |  3 |(3 rows)postgres=# select * from testnull where name is null;     ---只有2为null id | name----+------  2 |(1 row)postgres=# select * from testnull where name is  not null; id |  name   ----+---------  1 | feikong  3 |(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 feikong         2         3SQL> select * from testnull where name is null;   --2,3为null        ID NAME---------- ----------         2         3SQL> select * from testnull where name is  not null;        ID NAME---------- ----------         1 feikong

BY   丹心明月