Oracle 10g中对Merge语句的增强

在Oracle 10g之前，merge语句支持匹配更新和不匹配插入2种简单的用法，在10g中Oracle对merge语句做了增强，增加了条件选项和DELETE操作。下面我通过一个demo来简单介绍一下10g中merge的增强和10g前merge的用法。

　

参考Oracle 的SQL Reference，大家可以看到Merge Statement的语法如下：

MERGE [hint] INTO [schema .] table [t_alias] USING [schema .]

{ table | view | subquery } [t_alias] ON ( condition )

WHEN MATCHED THEN merge_update_clause

WHEN NOT MATCHED THEN merge_insert_clause;

下面我在windows xp 下10.2.0.1版本上做一个测试看看

SQL> select * from v$version;

BANNER

----------------------------------------------------------------

Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Prod

PL/SQL Release 10.2.0.1.0 - Production

CORE 10.2.0.1.0 Production

TNS for 32-bit Windows: Version 10.2.0.1.0 - Production

NLSRTL Version 10.2.0.1.0 - Production

SQL>

一、创建测试用的表

SQL> create table subs(msid number(9),

2 ms_type char(1),

3 areacode number(3)

4 );

表已创建。

SQL> create table acct(msid number(9),

2 bill_month number(6),

3 areacode number(3),

4 fee number(8,2) default 0.00);

表已创建。

SQL>

SQL> insert into subs values(905310001,0,531);

已创建 1 行。

SQL> insert into subs values(905320001,1,532);

已创建 1 行。

SQL> insert into subs values(905330001,2,533);

已创建 1 行。

SQL> commit;

提交完成。

SQL>

　

二、下面先演示一下merge的基本功能

1) matched 和not matched clauses 同时使用

merge into acct a

using subs b on (a.msid=b.msid)

when MATCHED then

update set a.areacode=b.areacode

when NOT MATCHED then

insert(msid,bill_month,areacode)

values(b.msid,'200702',b.areacode);

2) 只有not matched clause,也就是只插入不更新

merge into acct a

using subs b on (a.msid=b.msid)

when NOT MATCHED then

insert(msid,bill_month,areacode)

values(b.msid,'200702',b.areacode);

3) 只有matched clause, 也就是只更新不插入

merge into acct a

using subs b on (a.msid=b.msid)

when MATCHED then

update set a.areacode=b.areacode

Connected to Oracle Database 10g Enterprise Edition Release 10.2.0.1.0

Connected as study

SQL> select * from subs;

MSID MS_TYPE AREACODE

---------- ------- --------

905310001 0 531

905320001 1 532

905330001 2 533

SQL> select * from acct;

MSID BILL_MONTH AREACODE FEE

---------- ---------- -------- ----------

SQL>

SQL> merge into acct a

2 using subs b on (a.msid=b.msid)

3 when MATCHED then

4 update set a.areacode=b.areacode

5 when NOT MATCHED then

6 insert(msid,bill_month,areacode)

7 values(b.msid,'200702',b.areacode);

Done

SQL> select * from acct;

MSID BILL_MONTH AREACODE FEE

---------- ---------- -------- ----------

905320001 200702 532 0.00

905330001 200702 533 0.00

905310001 200702 531 0.00

SQL> insert into subs values(905340001,3,534);

1 row inserted

SQL> select * from subs;

MSID MS_TYPE AREACODE

---------- ------- --------

905340001 3 534

905310001 0 531

905320001 1 532

905330001 2 533

SQL>

SQL> merge into acct a

2 using subs b on (a.msid=b.msid)

3 when NOT MATCHED then

4 insert(msid,bill_month,areacode)

5 values(b.msid,'200702',b.areacode);

Done

SQL> select * from acct;

MSID BILL_MONTH AREACODE FEE

---------- ---------- -------- ----------

905320001 200702 532 0.00

905330001 200702 533 0.00

905310001 200702 531 0.00

905340001 200702 534 0.00

SQL> update subs set areacode=999;

4 rows updated

SQL> select * from subs;

MSID MS_TYPE AREACODE

---------- ------- --------

905340001 3 999

905310001 0 999

905320001 1 999

905330001 2 999

SQL> select * from acct;

MSID BILL_MONTH AREACODE FEE

---------- ---------- -------- ----------

905320001 200702 532 0.00

905330001 200702 533 0.00

905310001 200702 531 0.00

905340001 200702 534 0.00

SQL>

SQL> merge into acct a

2 using subs b on (a.msid=b.msid)

3 when MATCHED then

4 update set a.areacode=b.areacode;

Done

SQL> select * from acct;

MSID BILL_MONTH AREACODE FEE

---------- ---------- -------- ----------

905320001 200702 999 0.00

905330001 200702 999 0.00

905310001 200702 999 0.00

905340001 200702 999 0.00

SQL>

　

三、10g中增强一：条件操作

1) matched 和not matched clauses 同时使用

merge into acct a

using subs b on (a.msid=b.msid)

when MATCHED then

update set a.areacode=b.areacode

where b.ms_type=0

when NOT MATCHED then

insert(msid,bill_month,areacode)

values(b.msid,'200702',b.areacode)

where b.ms_type=0;

2) 只有not matched clause,也就是只插入不更新

merge into acct a

using subs b on (a.msid=b.msid)

when NOT MATCHED then

insert(msid,bill_month,areacode)

values(b.msid,'200702',b.areacode)

where b.ms_type=0;

3) 只有matched clause, 也就是只更新不插入

merge into acct a

using subs b on (a.msid=b.msid)

when MATCHED then

update set a.areacode=b.areacode

where b.ms_type=0;

Connected to Oracle Database 10g Enterprise Edition Release 10.2.0.1.0

Connected as study

SQL> select * from subs;

MSID MS_TYPE AREACODE

---------- ------- --------

905310001 0 531

905320001 1 532

905330001 2 533

SQL> select * from acct;

MSID BILL_MONTH AREACODE FEE

---------- ---------- -------- ----------

SQL>

SQL> merge into acct a

2 using subs b on (a.msid=b.msid)

3 when MATCHED then

4 update set a.areacode=b.areacode

5 where b.ms_type=0

6 when NOT MATCHED then

7 insert(msid,bill_month,areacode)

8 values(b.msid,'200702',b.areacode)

9 where b.ms_type=0;

Done

SQL> select * from acct;

MSID BILL_MONTH AREACODE FEE

---------- ---------- -------- ----------

905310001 200702 531 0.00

SQL> insert into subs values(905360001,0,536);

1 row inserted

SQL> select * from subs;

MSID MS_TYPE AREACODE

---------- ------- --------

905360001 0 536

905310001 0 531

905320001 1 532

905330001 2 533

SQL>

SQL> merge into acct a

2 using subs b on (a.msid=b.msid)

3 when NOT MATCHED then

4 insert(msid,bill_month,areacode)

5 values(b.msid,'200702',b.areacode)

6 where b.ms_type=0;

Done

SQL> select * from acct;

MSID BILL_MONTH AREACODE FEE

---------- ---------- -------- ----------

905310001 200702 531 0.00

905360001 200702 536 0.00

SQL> update subs set areacode=888 where ms_type=0;

2 rows updated

SQL> select * from subs;

MSID MS_TYPE AREACODE

---------- ------- --------

905360001 0 888

905310001 0 888

905320001 1 532

905330001 2 533

SQL> select * from acct;

MSID BILL_MONTH AREACODE FEE

---------- ---------- -------- ----------

905310001 200702 531 0.00

905360001 200702 536 0.00

SQL>

SQL> merge into acct a

2 using subs b on (a.msid=b.msid)

3 when MATCHED then

4 update set a.areacode=b.areacode

5 where b.ms_type=0;

Done

SQL> select * from acct;

MSID BILL_MONTH AREACODE FEE

---------- ---------- -------- ----------

905310001 200702 888 0.00

905360001 200702 888 0.00

SQL>

四、10g中增强二：删除操作

An optional DELETE WHERE clause can be used to clean up after a

merge operation. Only those rows which match both the ON clause

and the DELETE WHERE clause are deleted.

merge into acct a

using subs b on (a.msid=b.msid)

when MATCHED then

update set a.areacode=b.areacode

delete where (b.ms_type!=0);

SQL> select * from subs;

MSID MS_TYPE AREACODE

---------- ------- --------

905310001 0 531

905320001 1 532

905330001 2 533

SQL> select * from acct;

MSID MS_TYPE AREACODE

---------- ------- --------

905310001 0 531

905320001 1 532

905330001 2 533

SQL>

SQL> merge into acct a

2 using subs b on (a.msid=b.msid)

3 when MATCHED then

4 update set a.areacode=b.areacode

5 delete where (b.ms_type!=0);

Done

SQL> select * from acct;

MSID MS_TYPE AREACODE

---------- ------- --------

905310001 0 531

SQL>

更为详尽的语法，请参考Oracle SQL Reference手册！