oracle-merge用法详解(以示例说明)

在Oracle 10g以前，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语句作了加强，增长了条件选项和DELETE操做。下面我经过一个demo来简单介绍一下10g中merge的加强和10g前merge的用法。

　

参考Oracle 的SQL Reference，你们能够看到Merge Statement的语法以下：
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版本上作一个测试看看

SQL> select * from v$version;BANNER----------------------------------------------------------------Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - ProdPL/SQL Release 10.2.0.1.0 - ProductionCORE    10.2.0.1.0      ProductionTNS for 32-bit Windows: Version 10.2.0.1.0 - ProductionNLSRTL Version 10.2.0.1.0 - ProductionSQL> 1、建立测试用的表SQL> create table subs(msid number(9),  2                    ms_type char(1),  3                    areacode number(3)  4                    );表已建立。SQL> create table acct(msid number(9),  2                    bill_month number(6),  3                    areacode   number(3),  4                    fee        number(8,2) default 0.00);表已建立。SQL> SQL> insert into subs values(905310001,0,531);已建立 1 行。SQL> insert into subs values(905320001,1,532);已建立 1 行。SQL> insert into subs values(905330001,2,533);已建立 1 行。SQL> commit;提交完成。SQL> 　2、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 studySQL> select * from subs;      MSID MS_TYPE AREACODE---------- ------- -------- 905310001 0            531 905320001 1            532 905330001 2            533SQL> 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);DoneSQL> select * from acct;      MSID BILL_MONTH AREACODE        FEE---------- ---------- -------- ---------- 905320001     200702      532       0.00 905330001     200702      533       0.00 905310001     200702      531       0.00SQL> insert into subs values(905340001,3,534);1 row insertedSQL> select * from subs;      MSID MS_TYPE AREACODE---------- ------- -------- 905340001 3            534 905310001 0            531 905320001 1            532 905330001 2            533SQL> 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);DoneSQL> 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       0.00SQL> update subs set areacode=999;4 rows updatedSQL> select * from subs;      MSID MS_TYPE AREACODE---------- ------- -------- 905340001 3            999 905310001 0            999 905320001 1            999 905330001 2            999SQL> 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       0.00SQL> 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;DoneSQL> 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       0.00SQL> 　3、10g中加强一：条件操做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 studySQL> select * from subs;      MSID MS_TYPE AREACODE---------- ------- -------- 905310001 0            531 905320001 1            532 905330001 2            533SQL> 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;DoneSQL> select * from acct;      MSID BILL_MONTH AREACODE        FEE---------- ---------- -------- ---------- 905310001     200702      531       0.00SQL> insert into subs values(905360001,0,536);1 row insertedSQL> select * from subs;      MSID MS_TYPE AREACODE---------- ------- -------- 905360001 0            536 905310001 0            531 905320001 1            532 905330001 2            533SQL> 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;DoneSQL> select * from acct;      MSID BILL_MONTH AREACODE        FEE---------- ---------- -------- ---------- 905310001     200702      531       0.00 905360001     200702      536       0.00SQL> update subs set areacode=888 where ms_type=0;2 rows updatedSQL> select * from subs;      MSID MS_TYPE AREACODE---------- ------- -------- 905360001 0            888 905310001 0            888 905320001 1            532 905330001 2            533SQL> select * from acct;      MSID BILL_MONTH AREACODE        FEE---------- ---------- -------- ---------- 905310001     200702      531       0.00 905360001     200702      536       0.00SQL> 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;DoneSQL> select * from acct;      MSID BILL_MONTH AREACODE        FEE---------- ---------- -------- ---------- 905310001     200702      888       0.00 905360001     200702      888       0.00SQL> 4、10g中加强二：删除操做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            533SQL> select * from acct;      MSID MS_TYPE AREACODE---------- ------- -------- 905310001 0            531 905320001 1            532 905330001 2            533SQL> 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);DoneSQL> select * from acct;      MSID MS_TYPE AREACODE---------- ------- -------- 905310001 0            531SQL>