本文转自：http://blog.itpub.net/7204674/viewspace-468420/
分类： Linux
今天写程序的时候，遇到这样一个问题，假如存在记录则更新，不存在则插入。以前遇到这样的情况一般需要控制语句，游标来实现。偶然知道，MERGE语句，就可以实现Update和Insert的功能，特来实践一下。当然，首先来学习一下语法，看到oracle技术文档上是这样描述的：语法：merge::=De.ion of merge.gif followsmerge_update_clause ::=
De.ion of merge_update_clause.gif followsmerge_insert_clause ::=
De.ion of merge_insert_clause.gif followswhere_clause::=De.ion of where_clause.gif follows INTO 字句用于指定你所update或者Insert目的表。USING Clause用于指定你要update或者Insert的记录的来源，它可能是一个表，视图，子查询。ON Clause用于目的表和源表（视图，子查询）的关联，如果匹配（或存在），则更新，否则插入。merge_update_clause 用于写update语句merge_insert_clause用于写insert语句例子：
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> 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。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 0.0010g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 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>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 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 0 531说明：本文参考了oracle文档，例子是参考的http://xsb.itpub.net/post/419/30766。