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oracle merge into 的用法详解+实例

2016-01-13 08:56 851 查看
转:http://blog.csdn.net/shengchuang/article/details/5911858

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oracle merge into 的用法详解+实例

作用:merge into 解决用B表跟新A表数据,如果A表中没有,则把B表的数据插入A表;

1、建设银行:6227 0000 1068 0039 973 户名:郭永苏

开户行:北京海淀支行

语法:

MERGE INTO [your table-name] [rename your table here]

USING ( [write your query here] )[rename your query-sql and using just like a table]

ON ([conditional expression here] AND [...]...)

WHEN MATHED THEN [here you can execute some update sql or something else ]

WHEN NOT MATHED THEN [execute something else here ! ]

-------------------------------------实例-----------------------------------------------------------------

merge into tfa_alarm_act_nms a

using (select FP0,FP1,FP2,FP3,REDEFINE_SEVERITY

from tfa_alarm_status) b

on (a.fp0=b.fp0 and a.fp1=b.fp1 and a.fp2=b.fp2 and a.fp3=b.fp3)

when matched then update set a.redefine_severity=b.redefine_severity

when not matched then insert (a.fp0,a.fp1,a.fp2,a.fp3,a.org_severity,a.redefine_severity,a.event_time

,a.int_id)

values (b.fp0,b.fp1,b.fp2,b.fp3,b.REDEFINE_SEVERITY,b.redefine_severity,sysdate,7777778);

作用:利用表 tfa_alarm_status跟新表tfa_alarm_act_nms 的b.redefine_severity,条件是a.fp0=b.fp0 and a.fp1=b.fp1 and a.fp2=b.fp2 and a.fp3=b.fp3,如果tfa_alarm_act_nms表中没有该条件的数据就插入。

如果你的数据量很大,此sql效率非常高。

把数据从一个表复制到另一个表,插入新数据或替换掉老数据是每一个ORACLE DBA都会经常碰到的问题。在ORACLE9i以前的年代,我们要先查找是否存在老数据,如果有用UPDATE替换,否则用INSERT语句插入,其间少不了还有一些标记变量等等,繁琐的很。现在ORACLE9i专为这种情况提供了MERGE语句,使这一工作变得异常轻松,

MERGE语句在9i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;

例:

MERGE INTO tdest d

USING tsrc s ON (s.srckey = d.destkey)

WHEN MATCHED THEN

UPDATE SET d.destdata = d.destdata + s.srcdata

WHEN NOT MATCHED THEN

INSERT (destkey,destdata) VALUES (srckey,srcdata)

一条语句代替了原来的一段复杂语句,但是使用MERGE也是有要注意的地方的,看下面的例子:

CREATE TABLE tdest(destkey KEYTYE,destdata DATATYPE);

CREATE TABLE tsrc(srckey KEYTYE,srcdata DATATYPE);

--insert some rows into tsrc here.

MERGE INTO tdest d

USING tsrc s ON (d.destkey = s.srckey)

WHEN MATCHED THEN

UPDATE SET d.destkey = s.srckey

WHEN NOT MATCHED THEN

INSERT (d.destkey,d.destdata) VALUES (s.srckey,s.srcdata);

在Oracle 10g中MERGE有如下一些改进:

1、UPDATE或INSERT子句是可选的

2、UPDATE和INSERT子句可以加WHERE子句

3、在ON条件中使用常量过滤谓词来insert所有的行到目标表中,不需要连接源表和目标表

4、UPDATE子句后面可以跟DELETE子句来去除一些不需要的行

首先创建示例表:

create table PRODUCTS

(

PRODUCT_ID INTEGER,

PRODUCT_NAME VARCHAR2(60),

CATEGORY VARCHAR2(60)

);

insert into PRODUCTS values (1501, 'VIVITAR 35MM', 'ELECTRNCS');

insert into PRODUCTS values (1502, 'OLYMPUS IS50', 'ELECTRNCS');

insert into PRODUCTS values (1600, 'PLAY GYM', 'TOYS');

insert into PRODUCTS values (1601, 'LAMAZE', 'TOYS');

insert into PRODUCTS values (1666, 'HARRY POTTER', 'DVD');

commit;

create table NEWPRODUCTS

(

PRODUCT_ID INTEGER,

PRODUCT_NAME VARCHAR2(60),

CATEGORY VARCHAR2(60)

);

insert into NEWPRODUCTS values (1502, 'OLYMPUS CAMERA', 'ELECTRNCS');

insert into NEWPRODUCTS values (1601, 'LAMAZE', 'TOYS');

insert into NEWPRODUCTS values (1666, 'HARRY POTTER', 'TOYS');

insert into NEWPRODUCTS values (1700, 'WAIT INTERFACE', 'BOOKS');

commit;

1、可省略的UPDATE或INSERT子句

在Oracle 9i, MERGE语句要求你必须同时指定INSERT和UPDATE子句.而在Oracle 10g, 你可以省略UPDATE或INSERT子句中的一个. 下面的例子根据表NEWPRODUCTS的PRODUCT_ID字段是否匹配来updates表PRODUCTS的信息:

SQL> MERGE INTO products p

2 USING newproducts np

3 ON (p.product_id = np.product_id)

4 WHEN MATCHED THEN

5 UPDATE

6 SET p.product_name = np.product_name,

7 p.category = np.category;

3 rows merged.

SQL> SELECT * FROM products;

PRODUCT_ID PRODUCT_NAME CATEGORY

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

1501 VIVITAR 35MM ELECTRNCS

1502 OLYMPUS CAMERA ELECTRNCS

1600 PLAY GYM TOYS

1601 LAMAZE TOYS

1666 HARRY POTTER TOYS

SQL>

SQL> ROLLBACK;

Rollback complete.

SQL>

在上面例子中, MERGE语句影响到是产品id为1502, 1601和1666的行. 它们的产品名字和种 类被更新为表newproducts中的值. 下面例子省略UPDATE子句, 把表NEWPRODUCTS中新的PRODUCT_ID插入到表PRODUCTS中, 对于在两个表中能够匹配上PRODUCT_ID的数据不作任何处理. 从这个例子你能看到PRODUCT_ID=1700的行被插入到表PRODUCTS中.

SQL> MERGE INTO products p

2 USING newproducts np

3 ON (p.product_id = np.product_id)

4 WHEN NOT MATCHED THEN

5 INSERT

6 VALUES (np.product_id, np.product_name,

7 np.category);

1 row merged.

SQL> SELECT * FROM products;

PRODUCT_ID PRODUCT_NAME CATEGORY

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

1501 VIVITAR 35MM ELECTRNCS

1502 OLYMPUS IS50 ELECTRNCS

1600 PLAY GYM TOYS

1601 LAMAZE TOYS

1666 HARRY POTTER DVD

1700 WAIT INTERFACE BOOKS

2、带条件的Updates和Inserts子句

你能够添加WHERE子句到UPDATE或INSERT子句中去, 来跳过update或insert操作对某些行的处理. 下面例子根据表NEWPRODUCTS来更新表PRODUCTS数据, 但必须字段CATEGORY也得同时匹配上:

SQL> MERGE INTO products p

2 USING newproducts np

3 ON (p.product_id = np.product_id)

4 WHEN MATCHED THEN

5 UPDATE

6 SET p.product_name = np.product_name

7 WHERE p.category = np.category;

2 rows merged.

SQL> SELECT * FROM products;

PRODUCT_ID PRODUCT_NAME CATEGORY

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

1501 VIVITAR 35MM ELECTRNCS

1502 OLYMPUS CAMERA ELECTRNCS

1600 PLAY GYM TOYS

1601 LAMAZE TOYS

1666 HARRY POTTER DVD

SQL>

SQL> rollback;

在这个例子中, 产品ID为1502,1601和1666匹配ON条件但是1666的category不匹配. 因此MERGE命令只更新两行数据. 下面例子展示了在Updates和Inserts子句都使用WHERE子句:

SQL> MERGE INTO products p

2 USING newproducts np

3 ON (p.product_id = np.product_id)

4 WHEN MATCHED THEN

5 UPDATE

6 SET p.product_name = np.product_name,

7 p.category = np.category

8 WHERE p.category = 'DVD'

9 WHEN NOT MATCHED THEN

10 INSERT

11 VALUES (np.product_id, np.product_name, np.category)

12 WHERE np.category != 'BOOKS'

SQL> /

1 row merged.

SQL> SELECT * FROM products;

PRODUCT_ID PRODUCT_NAME CATEGORY

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

1501 VIVITAR 35MM ELECTRNCS

1502 OLYMPUS IS50 ELECTRNCS

1600 PLAY GYM TOYS

1601 LAMAZE TOYS

1666 HARRY POTTER TOYS

SQL>

注意由于有WHERE子句INSERT没有插入所有不匹配ON条件的行到表PRODUCTS.

3、无条件的Inserts

你能够不用连接源表和目标表就把源表的数据插入到目标表中. 这对于你想插入所有行到目标表时是非常有用的. Oracle 10g现在支持在ON条件中使用常量过滤谓词. 举个常量过滤谓词例子ON (1=0). 下面例子从源表插入行到表PRODUCTS, 不检查这些行是否在表PRODUCTS中存在:

SQL> MERGE INTO products p

2 USING newproducts np

3 ON (1=0)

4 WHEN NOT MATCHED THEN

5 INSERT

6 VALUES (np.product_id, np.product_name, np.category)

7 WHERE np.category = 'BOOKS'

SQL> /

1 row merged.

SQL> SELECT * FROM products;

PRODUCT_ID PRODUCT_NAME CATEGORY

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

1501 VIVITAR 35MM ELECTRNCS

1502 OLYMPUS IS50 ELECTRNCS

1600 PLAY GYM TOYS

1601 LAMAZE TOYS

1666 HARRY POTTER DVD

1700 WAIT INTERFACE BOOKS

6 rows selected.

SQL>

4、新增加的DELETE子句

Oracle 10g中的MERGE提供了在执行数据操作时清除行的选项. 你能够在WHEN MATCHED THEN UPDATE子句中包含DELETE子句. DELETE子句必须有一个WHERE条件来删除匹配某些条件的行.匹配DELETE WHERE条件但不匹配ON条件的行不会被从表中删除.

下面例子验证DELETE子句. 我们从表NEWPRODUCTS中合并行到表PRODUCTS中, 但删除category为ELECTRNCS的行.

SQL> MERGE INTO products p

2 USING newproducts np

3 ON (p.product_id = np.product_id)

4 WHEN MATCHED THEN

5 UPDATE

6 SET p.product_name = np.product_name,

7 p.category = np.category

8 DELETE WHERE (p.category = 'ELECTRNCS')

9 WHEN NOT MATCHED THEN

10 INSERT

11 VALUES (np.product_id, np.product_name, np.category)

SQL> /

4 rows merged.

SQL> SELECT * FROM products;

PRODUCT_ID PRODUCT_NAME CATEGORY

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

1501 VIVITAR 35MM ELECTRNCS

1600 PLAY GYM TOYS

1601 LAMAZE TOYS

1666 HARRY POTTER TOYS

1700 WAIT INTERFACE BOOKS

SQL>

产品ID为1502的行从表PRODUCTS中被删除, 因为它同时匹配ON条件和DELETE WHERE条件. 产品ID为1501的行匹配DELETE WHERE条件但不匹配ON条件, 所以它没有被删除. 产品ID为1700 的行不匹配ON条件, 所以被插入表PRODUCTS. 产品ID为1601和1666的行匹配ON条件但不匹配DELETE WHERE条件, 所以被更新为表NEWPRODUCTS中的值.
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