[20180904]工作中一个错误.txt

[20180904]工作中一个错误.txt

--//昨天看我提交一份修改建议,发现自己写的sql语句存在错误.
--//链接:http://blog.itpub.net/267265/viewspace-2213259/
--//里面提到:
5f2atm993xz6w
update PD_PMXS SET PDBZ =:"SYS_B_0" , STATUS =:"SYS_B_1" WHERE RDID =:1
修改为
update PD_PMXS SET PDBZ =:"SYS_B_0" , STATUS =:"SYS_B_1" WHERE RDID =:1 and  PDBZ <> :"SYS_B_0" and STATUS <>:"SYS_B_1"

--//这样修改是有问题,通过一个例子说明:

1.环境:
SCOTT@test01p> @ ver1

PORT_STRING                    VERSION        BANNER                                                                               CON_ID
------------------------------ -------------- -------------------------------------------------------------------------------- ----------
IBMPC/WIN_NT64-9.1.0           12.1.0.1.0     Oracle Database 12c Enterprise Edition Release 12.1.0.1.0 - 64bit Production              0

SCOTT@test01p> create table t (id number,a number,b number);
Table created.

insert into t values (1,0,0);
insert into t values (1,0,1);
insert into t values (1,1,0);
insert into t values (1,1,1);
insert into t values (1,2,2);
insert into t values (1,2,1);

commit;

2.测试:
SCOTT@test01p> select * from t where id=1 and a<>1 and b<>1;
        ID          A          B
---------- ---------- ----------
         1          0          0
         1          2          2

--//可以发现这样写仅仅显示两条.如果按照前面的语句执行dml,就存在错误了.

update PD_PMXS SET PDBZ =1 , STATUS =1 WHERE RDID =:1
--//修改为
update PD_PMXS SET PDBZ =1 , STATUS =1 WHERE RDID =:1 and PDBZ <>1 and STATUS <>1

--//这样仅仅(PDBZ, STATUS) =(0,0),(2,2) 才会修改.其它情况不会修改,实际上这是一个集合问题.
--//执行如下就对了.

SCOTT@test01p> select * from t where id=1 and (a<>1 or b<>1);
        ID          A          B
---------- ---------- ----------
         1          0          0
         1          0          1
         1          1          0
         1          2          2
         1          2          1

--//也就是我上面的语句要修改如下:
update PD_PMXS SET PDBZ =:"SYS_B_0" , STATUS =:"SYS_B_1" WHERE RDID =:1 and  (PDBZ <> :"SYS_B_0" or STATUS <>:"SYS_B_1" );

--//实际上面的写法很容易混乱,写成集合的形式就容易理解也不会错误.

SCOTT@test01p> select * from t where id=1 and (a,b) not in (1,1);
select * from t where id=1 and (a,b) not in (1,1)
                                            *
ERROR at line 1:
ORA-00920: invalid relational operator
--//集合还要加一个括号.

SCOTT@test01p> select * from t where id=1 and (a,b) not in ((1,1));
        ID          A          B
---------- ---------- ----------
         1          0          0
         1          0          1
         1          1          0
         1          2          2
         1          2          1


--//这样上面的修改如下:
5f2atm993xz6w
update PD_PMXS SET PDBZ =:"SYS_B_0" , STATUS =:"SYS_B_1" WHERE RDID =:1
修改为
update PD_PMXS SET PDBZ =:"SYS_B_0" , STATUS =:"SYS_B_1" WHERE RDID =:1 and  (PDBZ,STATUS) not in(( :"SYS_B_0" , :"SYS_B_1" );

--//这样也好理解也不会错误,给自己一个工作中提一个醒.