Primary keys and index

Hi,
   I got these question in interview Plz answer them
   1. Maximum number of primary keys u can use for a table?
   2. Maximum number of indexes u can create?
   3. Maximum number of secondary indexes?
   4. Maximum number fields in a table?
   5. Maximum length of primary key field?
Plz answer these questions
regards,
kumar

>>1. Maximum number of primary keys u can use for a table?
16
>>2. Maximum number of indexes u can create?
>>3. Maximum number of secondary indexes?
Only 16 Primary Index and n number of secondary indexes.
>>4. Maximum number fields in a table?
249
>>5. Maximum length of primary key field?
255
Cheers,
Hakim
Mark all useful answers..Close the thread once your question has been answered.

Similar Messages

Assigning primary key and index for a table

I have a database consisting of only one table with 10 million rows which mostly looks like this:
RECORDDATE                     ID     CLASS     VALUE
24-JAN-12 10.52.47.000000 AM     96     3     0
24-JAN-12 10.52.48.000000 AM     96     10     156
24-JAN-12 10.52.48.000000 AM     96     3     0
24-JAN-12 10.52.48.000000 AM     96     3     0
24-JAN-12 10.52.48.000000 AM     96     3     0
24-JAN-12 10.52.48.000000 AM     96     3     0
24-JAN-12 10.52.48.000000 AM     96     10     156
24-JAN-12 10.52.48.000000 AM     96     3     0
24-JAN-12 10.52.48.000000 AM     96     3     0
24-JAN-12 10.52.48.000000 AM     96     6     38
24-JAN-12 10.53.05.000000 AM     253     16     197
24-JAN-12 10.53.06.000000 AM     98     10     150
24-JAN-12 10.53.06.000000 AM     98     0     0
24-JAN-12 10.53.06.000000 AM     98     4     0
24-JAN-12 10.53.06.000000 AM     98     11     33As you can see there are several entries that look exactly the same. Currently, I don't have primary key or index for any column and have a lot of performance issues. For example this query takes more than 10 seconds to run:
select distinct      ID
from      scdatabase4
where ID < 253
order by 1Since database is not my primary job and have no background of it, I'm really confused about what to do to fix my issues. Could someone please help me in assigning primary key and index if you agree that this is the problem?!

Execute the query below to help decide what column to index:
SELECT COLUMN_NAME, NUM_DISTINCT, NUM_NULLS, NUM_BUCKETS, DENSITY
FROM DBA_TAB_COL_STATISTICS
WHERE TABLE_NAME = 'your_table_name'
ORDER BY COLUMN_NAME;
The important columns are:
1) NUM_DISTINCTS: Indicates the number of distinct values. If this number is very low for a column, it indicates that this column is not a very good candidate for a B-Tree index.
2) NUM_NULL: Indicates the number of null values for each column. A column with few null values is a good candidate for a index
But be aware, this is not a rule, it's just a method to help decide which column will have the most benefit of index creation.

Access path difference between Primary Key and Unique Index

Hi All,
Is there any specific way the oracle optimizer treats Primary key and Unique index differently?
Oracle Version
SQL> select * from v$version;
BANNER
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
PL/SQL Release 11.2.0.3.0 - Production
CORE    11.2.0.3.0      Production
TNS for IBM/AIX RISC System/6000: Version 11.2.0.3.0 - Production
NLSRTL Version 11.2.0.3.0 - Production
SQL> Sample test data for Normal Index
SQL> create table t_test_tab(col1 number, col2 number, col3 varchar2(12));
Table created.
SQL> create sequence seq_t_test_tab start with 1 increment by 1 ;
Sequence created.
SQL> insert into t_test_tab select seq_t_test_tab.nextval, round(dbms_random.value(1,999)) , 'B'||round(dbms_random.value(1,50))||'A' from dual connect by level < 100000;
99999 rows created.
SQL> commit;
Commit complete.
SQL> exec dbms_stats.gather_table_stats(USER_OWNER','T_TEST_TAB',cascade => true);
PL/SQL procedure successfully completed.
SQL> select col1 from t_test_tab;
99999 rows selected.
Execution Plan
Plan hash value: 1565504962
| Id | Operation         | Name       | Rows | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT |            | 99999 |   488K|    74   (3)| 00:00:01 |
|   1 | TABLE ACCESS FULL| T_TEST_TAB | 99999 |   488K|    74   (3)| 00:00:01 |
Statistics
          1 recursive calls
          0 db block gets
       6915 consistent gets
        259 physical reads
          0 redo size
    1829388 bytes sent via SQL*Net to client
      73850 bytes received via SQL*Net from client
       6668 SQL*Net roundtrips to/from client
          0 sorts (memory)
          0 sorts (disk)
      99999 rows processed
SQL> create index idx_t_test_tab on t_test_tab(col1);
Index created.
SQL> exec dbms_stats.gather_table_stats('USER_OWNER','T_TEST_TAB',cascade => true);
PL/SQL procedure successfully completed.
SQL> select col1 from t_test_tab;
99999 rows selected.
Execution Plan
Plan hash value: 1565504962
| Id | Operation         | Name       | Rows | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT |            | 99999 |   488K|    74   (3)| 00:00:01 |
|   1 | TABLE ACCESS FULL| T_TEST_TAB | 99999 |   488K|    74   (3)| 00:00:01 |
Statistics
          1 recursive calls
          0 db block gets
       6915 consistent gets
          0 physical reads
          0 redo size
    1829388 bytes sent via SQL*Net to client
      73850 bytes received via SQL*Net from client
       6668 SQL*Net roundtrips to/from client
          0 sorts (memory)
          0 sorts (disk)
      99999 rows processed
SQL> Sample test data when using Primary Key
SQL> create table t_test_tab1(col1 number, col2 number, col3 varchar2(12));
Table created.
SQL> create sequence seq_t_test_tab1 start with 1 increment by 1 ;
Sequence created.
SQL> insert into t_test_tab1 select seq_t_test_tab1.nextval, round(dbms_random.value(1,999)) , 'B'||round(dbms_random.value(1,50))||'A' from dual connect by level < 100000;
99999 rows created.
SQL> commit;
Commit complete.
SQL> exec dbms_stats.gather_table_stats('USER_OWNER','T_TEST_TAB1',cascade => true);
PL/SQL procedure successfully completed.
SQL> select col1 from t_test_tab1;
99999 rows selected.
Execution Plan
Plan hash value: 1727568366
| Id | Operation         | Name        | Rows | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT |             | 99999 |   488K|    74   (3)| 00:00:01 |
|   1 | TABLE ACCESS FULL| T_TEST_TAB1 | 99999 |   488K|    74   (3)| 00:00:01 |
Statistics
          1 recursive calls
          0 db block gets
       6915 consistent gets
          0 physical reads
          0 redo size
    1829388 bytes sent via SQL*Net to client
      73850 bytes received via SQL*Net from client
       6668 SQL*Net roundtrips to/from client
          0 sorts (memory)
          0 sorts (disk)
      99999 rows processed
SQL> alter table t_test_tab1 add constraint pk_t_test_tab1 primary key (col1);
Table altered.
SQL> exec dbms_stats.gather_table_stats('USER_OWNER','T_TEST_TAB1',cascade => true);
PL/SQL procedure successfully completed.
SQL> select col1 from t_test_tab1;
99999 rows selected.
Execution Plan
Plan hash value: 2995826579
| Id | Operation            | Name           | Rows | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT     |                | 99999 |   488K|    59   (2)| 00:00:01 |
|   1 | INDEX FAST FULL SCAN| PK_T_TEST_TAB1 | 99999 |   488K|    59   (2)| 00:00:01 |
Statistics
          1 recursive calls
          0 db block gets
       6867 consistent gets
          0 physical reads
          0 redo size
    1829388 bytes sent via SQL*Net to client
      73850 bytes received via SQL*Net from client
       6668 SQL*Net roundtrips to/from client
          0 sorts (memory)
          0 sorts (disk)
      99999 rows processed
SQL> If you see here the even though statistics were gathered,
     * In the 1st table T_TEST_TAB, the table is still using FULL table access after creation of index.
     * And in the 2nd table T_TEST_TAB1, table is using PRIMARY KEY as expected.
Any comments ??
Regards,
BPat

Thanks.
Yes, ignored the NOT NULL part.Did a test and now it is working as expected
SQL> create table t_test_tab(col1 number not null, col2 number, col3 varchar2(12));
Table created.
SQL>
create sequence seq_t_test_tab start with 1 increment by 1 ;SQL>
Sequence created.
SQL> insert into t_test_tab select seq_t_test_tab.nextval, round(dbms_random.value(1,999)) , 'B'||round(dbms_random.value(1,50))||'A' from dual connect by level < 100000;
99999 rows created.
SQL> commit;
Commit complete.
SQL> exec dbms_stats.gather_table_stats('GREP_OWNER','T_TEST_TAB',cascade => true);
PL/SQL procedure successfully completed.
SQL> set autotrace traceonly
SQL> select col1 from t_test_tab;
99999 rows selected.
Execution Plan
Plan hash value: 1565504962
| Id | Operation         | Name       | Rows | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT |            | 99999 |   488K|    74   (3)| 00:00:01 |
|   1 | TABLE ACCESS FULL| T_TEST_TAB | 99999 |   488K|    74   (3)| 00:00:01 |
Statistics
          1 recursive calls
          0 db block gets
       6912 consistent gets
          0 physical reads
          0 redo size
    1829388 bytes sent via SQL*Net to client
      73850 bytes received via SQL*Net from client
       6668 SQL*Net roundtrips to/from client
          0 sorts (memory)
          0 sorts (disk)
      99999 rows processed
SQL> create index idx_t_test_tab on t_test_tab(col1);
Index created.
SQL> exec dbms_stats.gather_table_stats('GREP_OWNER','T_TEST_TAB',cascade => true);
PL/SQL procedure successfully completed.
SQL> select col1 from t_test_tab;
99999 rows selected.
Execution Plan
Plan hash value: 4115006285
| Id | Operation            | Name           | Rows | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT     |                | 99999 |   488K|    63   (2)| 00:00:01 |
|   1 | INDEX FAST FULL SCAN| IDX_T_TEST_TAB | 99999 |   488K|    63   (2)| 00:00:01 |
Statistics
          1 recursive calls
          0 db block gets
       6881 consistent gets
          0 physical reads
          0 redo size
    1829388 bytes sent via SQL*Net to client
      73850 bytes received via SQL*Net from client
       6668 SQL*Net roundtrips to/from client
          0 sorts (memory)
          0 sorts (disk)
      99999 rows processed
SQL>

Difference between primary key and primary index

Dear All,
Hi... .Could you pls tell me the difference between primary key and primary index.
Thanks...

Hi,
Primary Key : It is one which makes an entry of the field unique.No two distinct rows in a table can have the same value (or combination of values) in those columns.
Eg: first entry is 111, if you again enter value 111 , it doesnot allow 111 again. similarly for the strings or characters or numc etc. Remember that for char or numc or string 'NAME' is not equal to 'name'.
Primary Index: this is related to the performance .A database index is a data structure that improves the speed of operations in a table. Indices can be created using one or more columns, providing the basis for both rapid random lookups and efficient ordering of access to records. The disk space required to store the index is typically less than the storage of the table (since indices usually contain only the key-fields according to which the table is to be arranged, and excludes all the other details in the table), yielding the possibility to store indices into memory from tables that would not fit into it. In a relational database an index is a copy of part of a table. Some databases extend the power of indexing by allowing indices to be created on functions or expressions. For example, an index could be created on upper(last_name), which would only store the uppercase versions of the last_name field in the index.
In a database , we may have a large number of records. At the time of retrieving data from the database based on a condition , it is a burden to the db server. so whenever we create a primary key , a primary index is automatically created by the system.
If you want to maintain indices on other fields which are frequently used in where condition then you can create secondary indices.
Reward points if helpful.
Thanks,
Sirisha..

Is their a difference between primary key and unique key with not null valu

What is the difference in having a column as primary key and having unique key with not null for the column.
vinodh

SBH wrote:
For quick review, below is the link
http://www.dba-oracle.com/data_warehouse/clustered_index.htm
You appear to have stumbled on a site that is a mine of disinformation about Oracle.
>
It would be helpful, if you explain it too..thnx !!
The site is wrong and makes up its own terminology as it goes along.
If the value for clustering factor approaches the number of blocks in the base table, then the index is said to be clustered. http://www.oracle.com/pls/db112/search?remark=quick_search&word=clustered+index
There is no create clustered index in Oracle.
- Clustering factor affects the efficiency of an index.
- There can be clustered tables that you can create indexes on.
- An Index Organized table is a similar concept to the Microsoft SQL Server clustered index, but it isn't the same thing at all.

PRIMARY KEY PARTITIONED INDEXES 생성방법 (ORA-2429, ORA-1408)

제품 : ORACLE SERVER
작성날짜 : 2004-08-13
PRIMARY KEY PARTITIONED INDEXES 생성방법 (ORA-2429, ORA-1408)
============================================================
PURPOSE
primary key partitioned indexes 를 생성하는 방법을 알아 봅니다.
SCOPE
Oracle Partitioning Option은 8~10g Standard Edition에서는 지원하지
않는다.
Example:
SQL> -- 먼저 partitioned table TEST_A 를 생성합니다.
SQL>
SQL> CREATE TABLE test_a (col1 number, col2 number, col3 varchar2(20))
2 PARTITION BY RANGE (col1, col2)
3 (partition part_test_a_1 values less than (10, 100),
4 partition part_test_a_2 values less than (20, 200),
5 partition part_test_a_3 values less than (30, 300),
6 partition part_test_a_4 values less than (40, 400));
Table created.
SQL> -- partitioned table TEST_B 를 생성합니다.
SQL>
SQL> CREATE TABLE test_b (col1 number, col2 number, col3 varchar2(20))
2 PARTITION BY RANGE (col1, col2)
3 (partition part_test_b_1 values less than (10, 100),
4 partition part_test_b_2 values less than (20, 200),
5 partition part_test_b_3 values less than (30, 300),
6 partition part_test_b_4 values less than (40, 400));
Table created.
SQL> -- TEST_A 테이블에
SQL> -- non-unique local partitioned index, IX_TEST_A 를 생성합니다.
SQL>
SQL> CREATE INDEX ix_test_a ON test_a(col1, col2)
2 LOCAL
3 (partition ix_test_a_1,
4 partition ix_test_a_2,
5 partition ix_test_a_3,
6 partition ix_test_a_4);
Index created.
SQL> -- TEST_B 테이블에
SQL> -- unique global partitioned index, IX_TEST_B 를 생성합니다.
SQL>
SQL> CREATE UNIQUE INDEX ix_test_b1 ON test_b(col1, col2)
2 GLOBAL PARTITION BY RANGE (col1, col2)
3 (partition ix_test_b1_1 values less than (20, 200),
4 partition ix_test_b1_2 values less than (maxvalue, maxvalue));
Index created.
SQL> -- TEST_A 테이블에 rimary key constraint (PK_TEST_A) 를 추가 합니다.
SQL>
SQL> ALTER TABLE test_a ADD CONSTRAINT pk_test_a
2 PRIMARY KEY (col2, col1);
Table altered.
SQL> -- index IX_TEST_A 를 drop 하려고 하면 다음 에러가 발생합니다.
SQL>
SQL> DROP INDEX ix_test_a;
drop index ix_test_a
ERROR at line 1:
ORA-02429: cannot drop index used for enforcement of unique/primary key
SQL> -- TEST_B 테이블에 partition IX_TEST_B1 에서 사용된 같은 columns 들을 사용해서
SQL> -- 새로운 두번째 index (IX_TEST_B2) 를 생성하려고 하면
SQL> -- 다음 에러가 발생합니다.
SQL>
SQL> CREATE INDEX ix_test_b2 ON test_b(col1, col2)
2 LOCAL;
create index ix_test_b2 on test_b(col1, col2)
ERROR at line 1:
ORA-01408: such column list already indexed
SQL> -- TEST_B 테이블에 primary key constraint (PK_TEST_B) 를 추가 합니다.
SQL>
SQL> ALTER TABLE test_b ADD CONSTRAINT pk_test_b
2 PRIMARY KEY (col1, col2);
Table altered.
SQL> -- index IX_TEST_B1 를 drop 하려고 하면 다음 에러가 발생합니다.
SQL>
SQL> DROP INDEX ix_test_b1;
drop index ix_test_b1
ERROR at line 1:
ORA-02429: cannot drop index used for enforcement of unique/primary key
SQL> -- indexes 들과 각 indexes 이 걸려있는 tables 의 목록입니다.
SQL>
SQL> SELECT index_name, partition_name, status
2 FROM user_ind_partitions
3 ORDER BY index_name, partition_name;
INDEX_NAME PARTITION_NAME STATUS
IX_TEST_A IX_TEST_A_1 USABLE
IX_TEST_A IX_TEST_A_2 USABLE
IX_TEST_A IX_TEST_A_3 USABLE
IX_TEST_A IX_TEST_A_4 USABLE
IX_TEST_B1 IX_TEST_B1_1 USABLE
IX_TEST_B1 IX_TEST_B1_2 USABLE
6 rows selected.
SQL> -- TEST_A 테이블에서 primary key constraint 를 drop 합니다.
SQL>
SQL> ALTER TABLE test_a DROP CONSTRAINT pk_test_a;
Table altered.
SQL> -- TEST_B 테이블에서 primary key constraint 를 drop 합니다.
SQL>
SQL> ALTER TABLE test_b DROP CONSTRAINT pk_test_b;
Table altered.
SQL> -- indexes 들과 각 indexes 이 걸려있는 tables 의 목록을 다시 봅니다.
SQL> -- 여기서 주의해서 보아야 할 것은 non-unique local partitioned index (IX_TEST_A)
SQL> -- 은 drop 되지 않고 USABLE 상태로 남아 있다는 것입니다.
SQL> -- 이렇게 되는 이유는 index (IX_TEST_A) 가 non-unique 이기 때문입니다.
SQL> -- 반면 unique global partitioned index (IX_TEST_B) 은 drop 되었습니다.
SQL>
SQL> SELECT index_name, partition_name, status
2 FROM user_ind_partitions
3 ORDER BY index_name, partition_name;
INDEX_NAME PARTITION_NAME STATUS
IX_TEST_A IX_TEST_A_1 USABLE
IX_TEST_A IX_TEST_A_2 USABLE
IX_TEST_A IX_TEST_A_3 USABLE
IX_TEST_A IX_TEST_A_4 USABLE
만일 index 가 primary key 에 정의되어 있는 columns 들과 같은 columns
을 사용해서 만들어 졌다면 primary key 는 그 underlying index 를 사용합니다.
이것은 index 가 unique 이건 non-unique 이건 또는 global 이건 local partioned index
이건 관계없이 적용됩니다.
위의 예제에서 primary key 가 non-unique index 위에 생성되었다는 것을
주의해 보시기 바랍니다. 이렇게 되는 이유는 index 안의 값들이 사실
모두 unique 하기 때문입니다. 그렇지 않을 경우 다음 에러가 발생하게 됩니다.
"ORA-02437: cannot enable (STEELY.PK_TEST_B) - primary key violated."
2개의 indexes 가 같은 순서의 같은 columns 을 사용해서 만들어 질 수는 없습니다.
위의 예제에서 TEST_B 테이블에 두번째 index (IX_TEST_B2) 를 만들려고
했을때 다음에러가 발생하는것을 확인할 수 있었습니다.
"ORA-01408: such column list already indexed."
하지만 columns 들의 순서를 바꾼다면 같은 columns 들을 사용하더라도
추가적으로 indexes 를 생성할 수 있습니다.
index (IX_TEST_A) 와 primary key (PK_TEST_A) 에 정의된 column 순서는
반대로 되어 있습니다. 그러나 primary key 는 IX_TEST_A 를 underlying index
로 사용하고 있습니다.
테이블에서 primary key constraint 가 drop 되었을때
만일 index 가 UNIQUE index 로 생성되었다면 대응하는 index 또한 drop 됩니다.
이 현상은 LOCAL 또는 GLOBAL partitioned indexes 모두에 적용됩니다.
partitioning 을 최대한 활용하기 위해서는 partitioned tables/indexes
를 생성할 때에 STORAGE clause 를 반드시 사용해야 합니다.
Reference Documents
<Note:74224.1>

First, thanks for posting the code that lets us reproduce your test. That is essential for issues like this.
Because the primary key is global you will not be able to use
INCLUDING INDEXES
WITH VALIDATION;And you will need to add the primary key to the temp table
ALTER TABLE DEMO_INTERVAL_DATA_LOAD_Y ADD CONSTRAINT IDX_DEMO_ROLL_Y PRIMARY KEY (ROLL_NUM);The the exchange will work. You will need to rebuild the primary key after the exchange.

Diff b/w primary key and unique key?

what is the diff b/w primary key and unique key?

Hi,
With respect to functionality both are same.
But in ABAP we only have Primary key for the Database tables declared in the Data Dictionary.
Unique is generally is the term used with declaring key's for internal tables.
Both primary and Unique keys can identify one record of a table.
Regards,
Sesh

Difference between PRIMARY KEY and UNIQUE KEY with NOT NULL

What is the difference between PRIMARY KEY and UNIQUE KEY with NOT NULL constraint?
Message was edited by:
Nilesh Hole

Answer for the master!!!
http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:8743855576462
Thanks,
Karthick

Primary keys and store generated pattern

Hi,
in my database first application (Firebird), the primary keys are not set to identity by default !
any ideas why this ?

Solved !
put #PK_GEN# as comment for your primary key and now EF import primary keys columns as identity like expeted :)
btw, fb 3.0 and up support identity columns .

Primary keys and constraints are gone....

Hi Experts,
I had a schema SchemaD with all primary keys and referential constraints. And i am a TOAD user. I had one more source schema SchemaS.
In my destination schema all the tables has 2 extra columns for data warehouse purpose.
I disabled all the constraints and i used toad utility "Copy Data to Another Schema" and i selected all the tables from Source SchemaS.
After the completion of data copy i tried to enable all the constraints in SchemaD. But i found that there are no primary keys and referential integrates in that schema.
Please help me in this issue.
Thanks...
Ray

Check in the views "DBA_CONSTRAINTS" or ALL_CONSTRAINTS" with the condition owner='your_schema_name'
If you are using toad to view the constraints, chances are high that there is a filter in the toad view and it is filtering the constraints...
Edited by: Suchit on Feb 25, 2009 5:19 PM
Edited by: Suchit on Feb 25, 2009 5:20 PM

Primary keys and foreign keys

Hi,
is there a script available for changing the value of a primary key which automaticly
detect all foreigs keys refering to this primary key and change them as well?
William Oorschot

I don't have the script now. but you can make a procedure of ur own.
using a join on user_constraints, and user_cons_columns you can find out all the columns in all the tables which are referencing the particular primary key. once you have the table and the referencing columns, you can change the value of those columns with the new value.
you'll have to call this procedure from a before row level trigger.
HTH
Naveen

Primary Key and Foreign Key Constraints

Hi All,
I would like to know PRIMARY KEY and FOREIGN KEY constraints on existing oracle tables. Could any one suggest me how to find out.
Thanks,
RED

You can query DBA_CONSTRAINTS to get a list of all the constraints on table A and/or table B. The documentation I linked to gives a full list of the data you can see in DBA_CONSTRAINTS, but it includes things like the referenced table name and referenced constraint name for a foreign key constraint. If A is a parent of B or B is a parent of A, you could match up the parent's primary key constraint to the child's foreign key constraint.
More generally, though, if you don't know that one of the tables is a parent of the other, figuring out how to join the two tables is probably not something that can be done using just the Oracle data dictionary. You would probably need an understanding of the data model being used to figure out what intermediate table(s) needed to be joined in order to relate rows in A to rows in B.
Justin

Primary key and WHO columns on EO

We are trying to create a EO based on a database view. We do not have primary key and standard OA WHO columns but the OA framework is forcing us the have these columns. How do we go about this issue? Any suggestion will be appreciated.

Oracle Apps mandates that you should have the Audit columns in the Applications tables.
So you must have the 5 columns defined.
I have created new tables for my application and need to populate them whenever user creates or modifies any row
Jdeveloper/BC4J handles direct updates/inserts through default EO implementation, it would insert/update/delete from the base table via the EO, what is your qeustion then ? do you want to know how to perform DMLs in OA or something else ?
Thanks
Tapash

Primary key and Foreign key on same column

Hi, I am able to create below tables , primary and foreign keys as below.
But Is this valid design? Can I define a column (ckey2 in table "child") as
primary key and as well as foreign key?
CREATE TABLE parent (
col1 NUMBER,
col2 NUMBER
CREATE TABLE child (
ckey1 NUMBER,
ckey2 NUMBER,
ckey3 NUMBER
alter table parent add constraint parent_pk primary key( col1 );
alter table child add constraint child_pk primary key( ckey2 );
alter table child add constraint child_fk foreign key( ckey2 ) references parent( col1);
Thanks.

Can I define a column (ckey2 in table "child") as primary key and as well as foreign key?You mean you want to define a one-to-one relationship between parent and child tables.. why would you want to do that ? You might as well merge the 2 tables into one.

Update a primary key and Fk

Hello
I have to update a primary key (PK) which is referenced by many foreign keys (FK).
The primary key columns cannot be updated as this would orphan the dependant tables,
and the dependant tables cannot be updated prior to the parent table as this would also make them orphans.
I think this problem was solved by disabling the foreign key constraints or deleting the original records and recreating them.
Since neither of these solutions is particularly satisfactory for me I read about 'deferred constraints'.
My question is:
Can I use(modify to) 'INITIALLY DEFERRED' keyword on constraints's table already created with The default, INITIALLY IMMEDIATE ,
that is, update my primary key and foreign keys, and then re-set to
'INITIALLY IMMEDIATE'? Or another trick exists ?
Thanks in advance for your attention

It is very popular the idea that the updates on primary key columns are a very bad thing.
Oracle supports this idea and that's why they don't give the "on update cascade" clause on foreign keys.
So in this case I suggest you to define a master table like this.
create table master_table (
     key_id number primary key,
     your_primary_key varchar2 not null unique
/Then you must use that key_id column as foreign key in place of your original primary key. In this way don't even need to update referencing rows when updating the original primary key because the foreign key value doesn't change and everything is always fine as before.
So instead to lose time implementing some strange sort of cascade triggers plain to do something like this on your schema.
insert into master_table (id_key,primary_key) (
     select rownum,primary_key
     from your_main_table
alter table your_main_table add (
     id_key number,
update your_main_table a
set id_key = (
          select b.id_key
          from master_table
          where b.primary_key=a.primary_key
     Drops foreign keys
alter table your_main_table drop primary key cascade
alter table your_main_table add constraint pk
     primary key(id_key)
alter table your_main_table add constraint fk
     foreign key(id_key) references master_table
alter table your_main_table drop (
     your_primary_key
alter table a_referencing_table add (
     id_key number,
update a_referencing_table a
set id_key = (
          select b.id_key
          from master_table
          where b.primary_key=a.primary_key
alter table a_referencing_table add constraint fk_2
     foreign key(id_key) references master_table
alter table a_referencing_table drop (
     your_primary_key
/If you have many objects referencing those tables I suggest you to rename the tables and to create views with the original name of the renamed tables that show data as it was before with a join on master_table. in this way you don't need to change the code of the application referencing them but you just need to recompile invalidated objects.
Bye Alessandro

Primary keys and index

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