UNION on two views in Different databases

Hi All,
Could you please help me in sorting out this requirement.
We have two views in one database and two more views in another database. Now I want to create one view which should give the union of all these four views. We have DB links. Is it possible? If yes please send me the script.
Thanks in advance to all.
Thanks & Regards
Rajesh Amathi

Hi and welcome to OTN.
please refer to Oracle books, your question is simple and also a few hard explained.
You can use union, union all, intersec and of course many join methods. Which one is for you, you should decide it, or let us know what exactly do you need.
If objects separated different databases, of course db link is necessary.
example of creation view:
CREATE VIEW sample_view AS
SELECT e1.Ename, e2.Empno, e1.Deptno
FROM table1 t1, table2 t2, table3@remotedb t3, table4@remotedb t4
WHERE t1.id = t2.id and t3.id=t4.id; --you can join all tables as you want
to overview of view please refer to : http://www.dba-oracle.com/concepts/views.htm
Edited by: Ulfet Tanriverdiyev on Aug 3, 2010 2:56 AM

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Using Oracle 10.2g
I have 2 databases Gus and haggis on Comqdhb schema.
glink indicates a databse link between Haggis and Gus
In Gus there are tables student,subject,grade,school containing columns like upn...
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upn
academicYear
SUBJECT
subject
GRADE
examlevel
grade
SCHOOL
sn
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upn
GRADE
grade
upn
academicyear
level
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create view as examGrade(upn, subject, examlevel, sn, grade,academicYear) as select s.upn
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I mean if i said
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ERROR at line 1:
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help me out,Thank you.

Thank you for the reply will follow up the code format
Create views in your HAGGIS schema database which will join all of the exam grades together. You should have one view which will produce the following relation :
examGrade(upn, subject, examlevel, sn, grade,academicYear)
I understand that there wont be duplication when we use conditions
If i query
select count(upn)
from   comqdhb.student@glink I get 9000
but after the union
create view examGrade(upn, subject, examlevel, sn, grade,academicYear)
as
select distinct s.upn as upn
,                  g.subject as subject
,                  g."LEVEL" as examlevel
,                  g.grade as grades
,                  '9364097'
,                  to_number(g.academicyear) as academicyear
from             comqdhb.student s
,                   comqdhb.grade g
where           s.upn=g.upn
union
select            s.upn
,                   sb.subject
,                   g.elevel
,                   g.grade
,                   s.acyr
,                   sc.sn
from              comqdhb.subject@glink sb
,                   comqdhb.student@glink s
,                    comqdhb.gradevalues@glink g
,                    comqdhb.school@glink sc,
,                    comqdhb.studentingroup@glink sg
,                    comqdhb.teachinggroup@glink tg
where            sb.sid=tg.sid
and                tg.gid=sg.gid
and                sg.upn=s.upn
and                g."LEVEL"=tg.elevel
and                s.school=sc.id
and                sc.id=tg.id; returns
count(upn) from exam gradeIt gets stuck actually sometimes it returns
932002 some results.
2:
Another problem i am having which i am trying to solve and written up my ideas but haven't been getting the expected results.Hope you can help.Thank you.
Information:
=======
All children take exams at the age of 16 called a General Certificate of SecondaryEducation (GCSE).
They have to study and take exams in Mathematics, English and Science, and can take other subjects such as History, French, Art etc. Most students will study between 5 and 10 different subjects before taking their GCSEs.
For each exam, a student is awarded a grade from A*, A, B,C,D,E,F,G,U,X An A* grade is the best grade achievable and an X is the worst grade.
In order to analyze how students have performed, each grade is mapped to a numeric value as follows:
Grade Numerical score
A* 8
A 7
B 6
C 5
D 4
E 3
F 2
G 1
U 0
X 0
Now why i need this avgGCSE is because i have to create a view containing avgGCSE of the students it is used in the next question where a condition is avgGCSE is between 6.5 and 7
In order to calculate the avgGCSE the idea is to calculate the grades of the students and map the grades to their corresponding scores/values
add them all up and div by the total no of grades to get the avg.
desc comqdhb.STUDENT@glink;
STUDENT
=======
UPN
FNAME
CNAME
DOB
GENDER
PREVIOUSSCHOOL
XGCSE
SCHOOL
ACYR
STUDENTINGROUP
=============
UPN
GID
STARTDATE
ENDDATE
GRADE
GRADEVALUES
===========
GRADE
LEVEL
VALUE
I have a opinion that xgcse in STUDENT table refers to the avgGCSE which i want to calculate as when i asked my professor as to what xgcse he said that he forgot to take it out of the table and it is not necessary while creating avggcse.
select *
from comqdhb.student@glink
where xgcse<6.5; Displaying a result
returns:
UPN FAMILYNAME COMMONNAME DATEOFBIR GENDER PREVIOUSSCHOOL XGCSE SCHOOL ACYR
===========================================================================
1011 KIMBERLY ABBOT 07-JUL-79 f none 3.93500948 2 2
select *
from comqdhb.student@glink
where xgcse between 6.5 and 7 and upn = 1386; Displaying a result
returns:
UPN FAMILYNAME COMMONNAME DATEOFBIR GENDER PREVIOUSSCHOOL XGCSE SCHOOL ACYR
===========================================================================
1386 STEPHANIE AANNESSON 15-JAN-79 f none 6.88873 2 2 so if xgcse is the avgGCSE then upn 1011 has avggcse<6.5 and 1386 has avggcse >6.5
my idea was backward strategy like so now if we find out upn 1368 has suppose xgcse(avggcse)>6.5 how to extract the avggcse for the particular upn We need to map grades from GRADEVALUES to grade in STUDENTINGROUP and map upn from studentingroup to upn in student to output the values for the corresponding grades from GRADEVALUES
select grade
from comqdhb.studentingroup@glink
where upn = 1011;
Result:
GRADE
=====
D
F
B
E
C
E
E
B
8 rows selected. Mapping each grade to the corresponding value and calculating we get
32/8=4 total(values to corresponding grades)/no of grades.
But the xgcse for upn 1011 is 3.935 and i am getting 4!! maybe xgcse isn't avggrade but ? is the procedure by me correct for calculating avggcse
select grade
from comqdhb.studentingroup@glink
where upn = 1386;
Result:
GRADE
======
A*
A*
A*
A*
B
A*
A*
A
B
B
B
11 rows selected. grade to the corresponding value and calculating we get
79/11=7.12 total(values to corresponding grades)/no of grades.
But the xgcse for upn 1011 is 6.88... and i am getting 7.12!!
But another problem
when i say
select   g.value,g.grade
from     comqdhb.gradevalues@glink g
,        comqdhb.studentingroup@glink sg
where    g.grade=sg.grade
and      sg.upn=1011;
result:
======
VALUE GRADE
===========
100 B
100 B
   80 C
   60 D
   40 E
   40 E
   40 E
   20 F
    6 B
    6 B
    5 C
VALUE GRADE
=============
    4 D
    3 E
    3 E
    3 E
    2 F
16 rows selected.
select   distinct g.value,g.grade
from     comqdhb.gradevalues@glink g
,        comqdhb.studentingroup@glink sg
where    g.grade=sg.grade
and      sg.upn=1011;
result:
======
VALUE GRADE
============
     2 F
   100 B
     6 B
     3 E
    60 D
     5 C
     4 D
    80 C
    40 E
    20 F
10 rows selected. I am getting only 8 for the query
select grade
from comqdhb.studentingroup@glink
where upn = 1386; here its becomming 10 and also its displaying values as 100 and ...
select distinct *
from   comqdhb.gradevalues@glink;
GRADEVALUES
===========
LEVEL      GRADE           VALUE
================================
a          A                 120
a          B                 100
a          C                  80
a          D                  60
a          E                  40
a          F                  20
a          U                   0
a          X                   0
g          A                   7
g          A*                  8
g          B                   6
LEVEL      GRADE           VALUE
================================
g          C                   5
g          D                   4
g          E                   3
g          F                   2
g          G                   1
g          U                   0
g          X                   0
18 rows selected. I was hoping if i could map the grades and get the values and calculate avggrade by total(values)/count(values)that would be it but here there are values like 100...
select sum(g.value)/count(g.grade) as avggrade
from    comqdhb.gradevalues@glink g
,         comqdhb.studentingroup@glink sg
where g.grade=sg.grade
and     sg.upn=1386;
avggrade
========
37.4375 the avggrade cant be this big and when i map each grade i obtained for 1368 like a to 7+b to 6 so on i get avggrade 7.12
kindly help.
Edited by: Trooper on Dec 15, 2008 4:49 AM

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<read-access>
<namespace-resource root="">
<security-role-mapping name="<jndi-user-role>">
<group name="administrators" />
</security-role-mapping>
</namespace-resource>
</read-access>
<write-access>
<namespace-resource root="">
<security-role-mapping name="<jndi-user-role>">
<group name="administrators" />
</security-role-mapping>
</namespace-resource>
</write-access>
</namespace-access>
</orion-application>

How to handle transactions when two different databases are involved.

consider two tables namely Table-A and Table-B part of two different databases namely ORACLE and MYSQL.
Now the project requirement is updating the Table-A(ORACLE) and Table-B (MYSQL) as one transaction. i.e. either update both the tables or rollback both the tables.
Now my question is how could i handle this situation using JDBC(Type-4) driver.Because i think at a time only one JDBC driver can be loaded into the JVM.

NareshAnkuskani wrote:
Now my question is how could i handle this situation using JDBC(Type-4) driver.Because i think at a time only one JDBC driver can be loaded into the JVM.No, that is not true.
But anyway, you need to use distributed (XA) transactions. i believe that the latest version (5.0) of mysql actually has support for XA transactions. you need to use a to setup a distributed transaction and attach the connections for the two databases to that transaction. then it should function as you desire.

Synch Between Tables in Two different Databases

Synch between Two Tables in two different Databases.
I have two identical tables, table T1 in Database D1 and table T1 in Database D2. User can insert/update/delete/select from both of these tables in respective databases. Being said that how can keep them in Synch? Any thing added/modified/deleted should reflect in other. We like this to be Real-Time.
We are thinking of creating a cross (two way) DB link between them and then update/insert/delete both the tables when changing one. Any suggestions?
Thanks

One of my colleagues used snapshot in their previous projects, but he told me that the performance of it wind down while the records in tables increase. I have no idea about the exact situation, but I'm believing we'd think twice about it.
eilison
[email protected]

Foreign Keys involving two different databases/schemas

Hi -- I'm wondering if it's possible to set a foreign key that involves tables that live in different databases/schemas. And, if it is possible, is it a horrible design idea?
Thanks,
~Christine

cav0227, you have asked two different two part questions.
1 - Is it possible to set up FK that span owners and is this good design?
Yes, it is possilbe and there if the data is related then yes it is good design. We like to minimize the number of object owners in our system and use a table naming standard where the first two or three letters of the table name represent a system code: ap, ar, gl for accounts receivable, accounts payable, and general ledger. Other may prefer to have an AP owner, AR owner, and a GL owner.
Ownership has no direct bearing on quality of design. If the tables are related then you should define the FK no matter who the owner is.
2 - Is it possible to define FK to remote (distributed) tables and is the good design? The answer is no. FK cannot reference remote objects. To enforce referencial integrity accross databases via the database, rather than in the application, requires the use of table triggers.
As far as good design that depends on why the data is remote and why the tables need to be linked. There are issues related to availability, recovery, and performance when data is distributed. Having such a relationship could be good design or bad design depending on if all the inter-related factors have been considered.
IMHO -- Mark D Powell --

UNION on two views in Different databases

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