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02.15.2008 at 03:24AM PST, ID: 23165684

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8.6

ensure certain combination of table data

Zones: Oracle Database, Oracle 10.x, PL / SQL

Tags: Oracle, 10 11

I have a table with a simple structure of:
CREATE TABLE test (PK int primary key, LK int not null, histtop char(1) not null)
What I want to ensure is the following:
There should only be one entry for the combination of LK and histtop='Y' (like a unique index), but there might be a lot of LK and histtop<>'Y'
So a unique index of LK and histtop does not work.
How can I ensure that constraint via database.
Valid example:
PK,LK,histtop
1,1,N
2,1,N
3,1,Y
4,2,Y

Invalid database state
1,1,N
2,1,Y
3,1,Y
4,2,Y

Is this possible and which oracle code would be needed for that?

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Question Stats

Zone: Database

Question Asked By: hernst42

Solution Provided By: sujith80

Participating Experts: 3

Solution Grade: A

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02.15.2008 at 03:35AM PST, ID: 20900848

Fekrat:

You can create a trigger everytime a record is inserted to check whether or not there is a record that contains LK and histtop equal to Y.

02.15.2008 at 03:36AM PST, ID: 20900850

Rank: Guru

jinesh_kamdar:

I can't think of a way to achieve this using a CHECK constraint since GROUP functions like COUNT are not allowed while defining constraints. A trigger may work though. Let me know if a trigger is fine with you and I can help you with how to do it.

02.15.2008 at 03:44AM PST, ID: 20900883

hernst42:

I currently use triggers, but they are not 100% valid because a select is run on the same table as the action happens.

INSERT seem to work ok, but update does not work and give an ORA-error (no Application error) as the same table is used.

So if you update a row which has hittop=Y (e.g. update another column) you get that ora-error (can check for that ora-code if needed, just haven't listed that one here.

Should have posted the triggers directly, sorry. Maybe there is another way for using the triggers.

                       
             CREATE OR REPLACE TRIGGER htcu_Testtable BEFORE UPDATE ON Testtable FOR EACH ROW when (new."histtop" = 'Y') DECLARE num int; BEGIN SELECT count(*) INTO num FROM Testtable WHERE Testtable."histtop"='Y' AND Testtable."LK"=:new."LK" AND Testtable."PK"<>:new."PK"; if (num > 0) THEN RAISE_APPLICATION_ERROR (num => -20000, msg => 'duplicate histtop'); END IF; END;
/
CREATE OR REPLACE TRIGGER htci_Testtable BEFORE INSERT ON Testtable FOR EACH ROW when (new."histtop" = 'Y') DECLARE num int; BEGIN SELECT count(*) INTO num FROM Testtable WHERE Testtable."histtop"='Y' AND Testtable."LK"=:new."LK"; if (num > 0) THEN RAISE_APPLICATION_ERROR (num => -20000, msg => 'duplicate histtop'); END IF; END;
/

Open in New Window

02.15.2008 at 03:57AM PST, ID: 20900936

hernst42:

Ok here is the Ora-code: ORA-04091
ORA-04091: Table Testtable mutating, trigger/function may not see it

02.15.2008 at 05:13AM PST, ID: 20901303

Fekrat:

The main reason behind the ORA-04091 is that your trying to use a select statement on a table that is being modified which is not allowed and the only way to resolve this error is through removing the select statement that is being done on the table. Therefore i would i advise that you change the trigger to after update instead of before.

02.15.2008 at 05:20AM PST, ID: 20901358

Fekrat:

In addition to what i said earlier you will have to use the new and old values to be able to undo whatever has been updated in case it was not acceptable

02.15.2008 at 06:43AM PST, ID: 20902084

hernst42:

So using the trigger as:

CREATE OR REPLACE TRIGGER htcu_Testtable AFTER UPDATE ON Testtable FOR EACH ROW when (new."histtop" = 'Y') DECLARE num int; BEGIN SELECT count(*) INTO num FROM Testtable WHERE Testtable."histtop"='Y' AND Testtable."LK"=:new."LK" AND Testtable."PK"<>:new."PK"; if (num > 0) THEN RAISE_APPLICATION_ERROR (num => -20000, msg => 'duplicate histtop'); END IF; END;

will do the trick? I don't really care about restoring the correct value. In this case the UPDATE will fail with an application error and the complete transaction is rolled back. I will try that on Monday and report back.

02.15.2008 at 08:40AM PST, ID: 20903379

Rank: Guru

jinesh_kamdar:

No, that won't work either. You will have to use a statement-level trigger, something like below.

                       
         
           
           
             CREATE OR REPLACE TRIGGER htciu_TestTable
   AFTER INSERT OR UPDATE
   ON TestTable
DECLARE
   cnt   INT;
   dcnt  INT;
BEGIN
   SELECT COUNT(lk), COUNT(DISTINCT lk)
     INTO cnt, dcnt
     FROM TestTable
    WHERE histtop = 'Y';
 
   IF cnt <> dcnt THEN
      RAISE_APPLICATION_ERROR(num => -20000, msg => 'duplicate histtop');
   END IF;
END htciu_TestTable;
/

           
         

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02.15.2008 at 08:50AM PST, ID: 20903484

Rank: Sage

sujith80:

I guess the best is to handle this case programmatically,
See a dirty workaround below.

                       
         
           
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             drop table test
/
drop sequence test_seq
/
CREATE TABLE test (PK int primary key, LK int not null, histtop char(1) not null,dummy_col number)
/
create sequence test_seq start with 1 increment by 1
/
create unique index test_idx on test(LK, dummy_col)
/
create trigger test_trg
before insert on test
for each row
declare
 l_n number;
begin
 if :new.histtop = 'Y' then
  :new.dummy_col := null;
 else
  select test_seq.nextval into :new.dummy_col from dual;
 end if;
end;
/
insert into test(PK, LK, histtop) values( 1,1,'N');
insert into test(PK, LK, histtop) values( 2,1,'Y');
insert into test(PK, LK, histtop) values( 3,1,'Y');
insert into test(PK, LK, histtop) values( 4,2,'Y');

           
         

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02.15.2008 at 09:27AM PST, ID: 20903878

Rank: Sage

sujith80:

Pls ignore the above comment. This is a better workaround to do it.

                       
         
           
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             drop table test
/
CREATE TABLE test (PK int primary key, LK int not null, histtop char(1) not null )
/
create or replace function test_func1(par char)
return char
deterministic
as
begin
 if par = 'Y' then
  return par;
 else 
  return null;
 end if;
end;
/
create or replace function test_func2(par1 int, par2 char)
return int
deterministic
as
begin
 if par2 = 'Y' then 
  return par1;
 else 
  return null;
 end if;
end;
/
create unique index test_idx on test(test_func2(LK, histtop), test_func1(histtop))
/
 
insert into test values( 1,1,'N');
insert into test values( 2,1,'Y');
insert into test values( 3,1,'Y');
insert into test values( 4,2,'Y');

           
         

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02.15.2008 at 09:39AM PST, ID: 20903996

Rank: Sage

sujith80:

Well that further simplifies into this.
A single function based index will do it.

                       
         
           
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             CREATE TABLE test (PK int primary key, LK int not null, histtop char(1) not null )
/
create or replace function test_func2(par1 int, par2 char)
return int
deterministic
as
begin
 if par2 = 'Y' then 
  return par1;
 else 
  return null;
 end if;
end;
/
create unique index test_idx on test(test_func2(LK, histtop))
/
 
insert into test values( 1,1,'N');
insert into test values( 2,1,'Y');
insert into test values( 3,1,'Y');
insert into test values( 4,2,'Y');

           
         

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Accepted Solution

02.16.2008 at 09:53PM PST, ID: 20913131

Rank: Guru

jinesh_kamdar:

@sujith80: When I tried that in my DB, I'm getting insufficient privileges error i.e. whenever I try to create any function-based UNIQUE index. Do i need to get the DBA to provide me any specific grant to achieve this?

02.17.2008 at 03:06AM PST, ID: 20913661

Rank: Sage

sujith80:

Hi jinesh_kamdar: You should have the QUERY REWRITE prvilege to create function based indexes. Hope the function is owned by the same user. Otherwise the user must be granted execute privilege on the function as well.

02.17.2008 at 12:06PM PST, ID: 20915276

Rank: Guru

jinesh_kamdar:

Hi Sujith, I created the table and function under SCOTT, so it would obviously have the EXECUTE privilege on test_func2. However, when I tried to create the function-based index on the table, it didn't work, even without the UNIQUE specifier citing - "insufficient privileges"! Do u think I still need the QUERY REWRITE privilege to be granted to SCOTT? Thx for the response.

                       
         
           
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             Enter user-name: SCOTT
Enter password: *****
 
Connected to:
Oracle9i Enterprise Edition Release 9.0.1.1.1 - Production
With the Partitioning option
JServer Release 9.0.1.1.1 - Production
 
SQL> CREATE TABLE test (PK int primary key, LK int not null, histtop char(1) not null )
/
 
Table created.
 
SQL> create or replace function test_func2(par1 int, par2 char)
return int
deterministic
as
begin
 if par2 = 'Y' then 
  return par1;
 else 
  return null;
 end if;
end;
/
 
Function created.
 
SQL> create unique index test_idx on test(test_func2(LK, histtop))
/
create unique index test_idx on test(test_func2(LK, histtop))
                                                    *
ERROR at line 1:
ORA-01031: insufficient privileges
 
 
SQL> 

           
         

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02.17.2008 at 12:07PM PST, ID: 20915284

Rank: Guru

jinesh_kamdar:

Posting the end part of the output ...

                       
         
           
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             ...
Function created.
 
SQL> create unique index test_idx on test(test_func2(LK, histtop))
  2  /
create unique index test_idx on test(test_func2(LK, histtop))
                                                    *
ERROR at line 1:
ORA-01031: insufficient privileges
 
 
SQL> create index test_idx on test(test_func2(LK, histtop))
  2  /
create index test_idx on test(test_func2(LK, histtop))
                                             *
ERROR at line 1:
ORA-01031: insufficient privileges
 
 
SQL> 

           
         

Open in New Window

02.18.2008 at 01:34AM PST, ID: 20918658

Rank: Sage

sujith80:

Are you able to create a function based index on a standard oracle function, like trim, trunc etc?
What is the value of COMPATIBLE in your database? What is the version of database?

02.18.2008 at 05:30AM PST, ID: 20919662

Rank: Guru

jinesh_kamdar:

Nope, i could not even create an index for the emp table on UPPER(ename). Its a 9i DB on Win XP. How do i check the COMPATIBLE value?

hernst42

02.18.2008 at 07:06AM PST, ID: 20920452

I accepted that solution, as it additional ships me around another problem and I don't need to make any modification to my current Database structure and also don't need to create temp tables.

hernst42

02.18.2008 at 07:08AM PST, ID: 20920457

Additional Info. The user where I tested it was created with the following SQL:
grant create session, create procedure, create sequence, create table, create trigger, alter session to $sqluser

sujith80

02.18.2008 at 06:53PM PST, ID: 20925338

@jinesh_kamdar:
pls grant QUERY REWRITE to the user and try.
you can see the value of COMPATIBLE from v$Parameter.

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