在两个数据库之间进行数据同步

OLAP的第一步就是从业务系统中抽取数据到数据仓库系统。
除了ETL工具Kettle，也可以使用PL/SQL

创建Source表，模拟业务系统的数据表。
create table source as select sys_guid() id ,o.* from dba_objects o where rownum<1000;
alter table source add constraint PK_source primary key (id);

创建Target表，模拟数据仓库中的表。
create table target as select * from source where 1=0;
alter table target add constraint PK_target primary key (id);

创建DB LINK，remote模拟业务系统的数据库
create database link remote connect to username identified by xxxxxx using 'remote';

因为业务系统的数据是变化的，相较于数据仓库的表，他可能更新了一些数据，也可能修改了一些数据。
比对业务表和数据仓库表的数据，
如果ID相同，并且数据有变化
则根据ID更新数据仓库的表(target)
如果业务系统的数据ID(source)，还没有出现在数据仓库的表中(target)
则在数据仓库的表中新增这个记录。

本质都是Oracle Merge的功能，只不过尝试另外几种方法。

1.merge

mergeintotarget tusing(select*fromsource@remote)s
on(t.id=s.id)
when matched
then
updateset t.owner=s.owner,
t.object_name=s.object_name,
t.subobject_name=s.subobject_name,
t.object_id=s.object_id,
t.data_object_id=s.data_object_id,
t.object_type=s.object_type,
t.created=s.created,
t.last_ddl_time=s.last_ddl_time,
t.timestamp=s.timestamp,
t.status=s.status,
t.temporary=s.temporary,
t.generated=s.generated,
t.secondary=s.secondary,
t.namespace=s.namespace,
t.edition_name=s.edition_name
whennotmatched
then
insertvalues
(
s.id,
s.owner,
s.object_name,
s.subobject_name,
s.object_id,
s.data_object_id,
s.object_type,
s.created,
s.last_ddl_time,
s.timestamp,
s.status,
s.temporary,
s.generated,
s.secondary,
s.namespace,
s.edition_name
);

2.全局临时表。
首先将远程业务系统的数据放入临时表，
然后根据ID更新数据，如果数据的内容没有变化，则不更新。
最后插入业务系统中新建的数据。

createglobal temporarytabletmp
oncommit preserverows
as
select*fromtargetwhere1=0;

insertintotmpselect*fromsource@remote;

updatetarget tset
(
t.owner,
t.object_name,
t.subobject_name,
t.object_id,
t.data_object_id,
t.object_type,
t.created,
t.last_ddl_time,
t.timestamp,
t.status,
t.temporary,
t.generated,
t.secondary,
t.namespace,
t.edition_name
)
=
(select
tmp.owner,
tmp.object_name,
tmp.subobject_name,
tmp.object_id,
tmp.data_object_id,
tmp.object_type,
tmp.created,
tmp.last_ddl_time,
tmp.timestamp,
tmp.status,
tmp.temporary,
tmp.generated,
tmp.secondary,
tmp.namespace,
tmp.edition_name
fromtmpwheret.id=tmp.id)
whereexists(
select*fromtmpwheretmp.id=t.idandnot(
tmp.owner=t.ownerand
tmp.object_name=t.object_nameand
tmp.subobject_name=t.subobject_nameand
tmp.object_id=t.object_idand
tmp.data_object_id=t.data_object_idand
tmp.object_type=t.object_typeand
tmp.created=t.createdand
tmp.last_ddl_time=t.last_ddl_timeand
tmp.timestamp=t.timestampand
tmp.status=t.statusand
tmp.temporary=t.temporaryand
tmp.generated=t.generatedand
tmp.secondary=t.secondaryand
tmp.namespace=t.namespaceand
tmp.edition_name=t.edition_name
)
);

insertintotarget
select*fromtmpwherenotexists(
select*fromtarget twheret.id=tmp.id);

3.集合处理
为了简单，没有进行内容变化的判断

declare
typetabistableoftarget%rowtype;
l_rowtab;
cursor curisselect*fromsource@remote;
begin
open cur;
fetch cur bulk collectintol_row;
close cur;
forall iin1..l_row.count
updatetargetsetrow=l_row(i)whereid=l_row(i).id;
insertintotargetselect*fromsource@remote
 s
wherenotexists(select*fromtarget
 twheret.id=s.id);
commit;
end;
/

4.内联视图更新
没有写更新后插入的步骤，插入的实现是相同的。

update(
select
s.id s1,
s.owner s2,
s.object_name s3,
s.subobject_name s4,
s.object_id s5,
s.data_object_id s6,
s.object_type s7,
s.created s8,
s.last_ddl_time s9,
s.timestamp s10,
s.status s11,
s.temporary s12,
s.generated s13,
s.secondary s14,
s.namespace s15,
s.edition_name s16,
t.id t1,
t.owner t2,
t.object_name t3,
t.subobject_name t4,
t.object_id t5,
t.data_object_id t6,
t.object_type t7,
t.created t8,
t.last_ddl_time t9,
t.timestamp t10,
t.status t11,
t.temporary t12,
t.generated t13,
t.secondary t14,
t.namespace t15,
t.edition_name t16
fromtarget t inner join source@remote son(s.id=t.id)
where
not
(
s.owner=t.ownerand
s.object_name=t.object_nameand
s.subobject_name=t.subobject_nameand
s.object_id=t.object_idand
s.data_object_id=t.data_object_idand
s.object_type=t.object_typeand
s.created=t.createdand
s.last_ddl_time=t.last_ddl_timeand
s.timestamp=t.timestampand
s.status=t.statusand
s.temporary=t.temporaryand
s.generated=t.generatedand
s.secondary=t.secondaryand
s.namespace=t.namespaceand
s.edition_name=t.edition_name
)
)
set
t1=s1,
t2=s2,
t3=s3,
t4=s4,
t5=s5,
t6=s6,
t7=s7,
t8=s8,
t9=s9,
t10=s10,
t11=s11,
t12=s12,
t13=s13,
t14=s14,
t15=s15,
t16=s16
;

5.Minus
先插入业务表中新增的记录，然后对比修改。

declare
typetabistableoftarget%rowtype;
l_rowtab;
cursor curisselect*fromsource@remoteminusselect*fromtarget;
begin
insertintotargetselect*fromsource@remote
 s
wherenotexists(select*fromtarget
 twheret.id=s.id);
open cur;
fetch cur bulk cllectintol_row;
close cur;
forall iin1..l_row.count
updatetargetsetrow=low(i)whereid=l_row(i).id;
commit;
end;
/