SQL & PL/SQL :: Normalization - Concept Of Primary Key / Composite Key
May 17, 2013
I am following Lynda Tutorial for Normalization. I have understand normalization.The core concept of primary key is that it uniquely identifies each record in the table, but here in the given below image the 'COURSE' field is repeating 'SQL101' value again and again but still the teacher in the video is calling it primary key and combination of date & Course column Composite key.how can a field which vales are repeating can be called as Primary Key?
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Jun 24, 2013
the database normalization concept. I have gone through couple of blogs and the websites but even i am not clear about the 1NF, 2NF, 3NF, Boycee Code etc, may be i am missing the basic points. give me some example notes / more clear precise information to understand the concepts clearly.
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Jun 26, 2012
understanding composite primary key.
I know what is composite key and how it stores the data.. but i am not able to find when i have to choose the columns to be composite keys.
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May 20, 2010
I have the following 3 columns in my VERSIONS table.
MAJOR
MINOR
MICRO
The MAJOR,MINOR and MICRO columns create a unique composite primary key. I need to query out the last version by doing the following 3 queries and combine them.
select max(major) as max_major from versions
select max(minor) as max_minor from versions where major = :max_major
select max(micro) as max_micro from versions where minor = max_minor and major = max_major
Is there any way I can query out max(major),max(minor),max(micro) in a single query.
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Jul 4, 2013
I have to create six tables as part of my assignment. I have created 5 tables. I am having trouble with the 6th. How can I reference a foreign key to a composite primary key? I have colored red the areas that I think are giving me trouble which is in the 6th table, the Registration Table.
Create Table Student
(
StudentID number (6,0) NOT NULL,
Student_Name varchar2 (20) NOT NULL,
Constraint Student_PK Primary Key (StudentID)
);
Create Table Faculty
(
FacultyID number (5,0) NOT NULL,
Faculty_Name varchar2 (20) NOT NULL,
Constraint Faculty_PK Primary Key (FacultyID)
);
Create Table Course
(
CourseID varchar2 (10) NOT NULL,
Course_Name varchar2 (20) NOT NULL,
Constraint Course_PK Primary Key (CourseID)
);
Create Table Qualified
(
FacultyID number (5,0) NOT NULL,
CourseID varchar2 (10) NOT NULL,
Date_Qualified varchar2 (10) NOT NULL,
Constraint Qualified_PK Primary Key (FacultyID, CourseID),
Constraint Qualified_FK1 Foreign Key (FacultyID) references Faculty (FacultyID),
Constraint Qualified_FK2 Foreign Key (CourseID) references Course (CourseID)
);
Create Table Section
(
Section_No number (5,0) NOT NULL,
Semester varchar2 (7) NOT NULL,
CourseID varchar2 (12) NOT NULL,
Constraint Section_PK Primary Key (Section_No, Semester, CourseID),
Constraint Section_FK Foreign Key (CourseID) references Course (CourseID)
);
Create Table Registration
(
StudentID number (6,0) NOT NULL,
Section_No number (5,0) NOT NULL,
Semester varchar2 (7) NOT NULL,
Constraint Registration_PK Primary Key (StudentID, Section_No, Semester),
Constraint Registration_FK1 Foreign Key (StudentID) references Student (StudentID),
Constraint Registration_FK2 Foreign Key (Section_No) references Section (Section_No, Semester, CourseID),
Constraint Registration_FK3 Foreign Key (Semester) references Section (Section_No, Semester, CourseID)
);
This is the error I am receiving:
Error starting at line 1 in command:
Create Table Registration
(
StudentID number (6,0) NOT NULL,
Section_No number (5,0) NOT NULL,
Semester varchar2 (7) NOT NULL,
Constraint Registration_PK Primary Key (StudentID, Section_No, Semester),
Constraint Registration_FK1 Foreign Key (StudentID) references Student (StudentID),
Constraint Registration_FK2 Foreign Key (Section_No) references Section (Section_No, Semester, CourseID),
Constraint Registration_FK3 Foreign Key (Semester) references Section (Section_No, Semester, CourseID)
)
Error at Command Line:8 Column:104
Error report:
SQL Error: ORA-02256: number of referencing columns must match referenced columns
02256. 00000 - "number of referencing columns must match referenced columns"
*Cause: The number of columns in the foreign-key referencing list is not equal to the number of columns in the referenced list.
*Action: Make sure that the referencing columns match the referenced columns.
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Jan 21, 2012
I have an employee table which has a primary key and a self referencing foreign key, as shown here
create table employee (
id not null,
name not null,
department not null,
supervisor_id not null
,constraint constraint_1 primary key (id)
,constraint constraint_2 foreign key (supervisor_id) references employee (id));
Now if i make the primary key composite, as shown below -
create table employee (
id not null,
name not null,
department not null,
supervisor_id not null
,constraint constraint_1 primary key (id, name)
,constraint constraint_2 foreign key (supervisor_id) references employee (id));
Oracle is throwing the following error -
ORA-02270: no matching unique or primary key for this column-list
How can this error be fixed without changing the composite primary key?
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Jun 22, 2009
Provide material for External table concept .which is like exactly as SQL * Loader concept.
What are the basic difference between External table concept and SQL * Loader concept.
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Oct 20, 2010
Any links on hierarchical retrieval concepts?
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Nov 6, 2011
How a DB client session establishes a connection and how it performs any transaction.
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May 29, 2012
what is ISP concept in Oracle10g???
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Dec 8, 2011
Do Oracle SQL support Domain Concept?
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Jul 25, 2013
concept of composite and candidate keys. i have gone through all the definition part but did not understand the concept of creating candidate key for example:-
composite key
create table test(id number,pincode number(4),name varchar2(15),primary key(id,pincode));
table created with composite bcz i took pair of id and pincode.
here base on the same example want to create candidate key with the syntax.
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Dec 10, 2011
what is the process of creating log file in database, Suppose if we have two user ,and both are logon through id & password,at that condition i want all log file from users who done at the database like any events.
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Sep 21, 2012
What is Stripping concept in Automatic Storage Management?
How it spreads the database files across the disk group (Suppose i am having 4 disks in my disk group)?
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Oct 11, 2011
I have the following case:
create table try_o
(pk1 NUMBER, pk2 NUMBER, fld1 VARCHAR2(10), fld2 NUMBER,
PRIMARY KEY (pk1, pk2));
insert ALL
into try_o values (1,1,'f1',5)
into try_o values (1,2,'f1',5)
[Code]....
I need to get the row that contains the least pk2 among the group of records with the same fld1 and fld2. but if I used
select min(pk1), min(pk2), fld1, fld2
from TRY_o
group by fld1, fld2;
I get a record that doesn't exists as the min(pk1) and min(pk2) are from different records. I need to get the min(pk1) and its corresponding pk2.
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Nov 8, 2012
I have a lot of queries on a table with WHERE clause:
WHERE CR_DATE > :y AND CR_VALUE = :x
Actually, there is an index on (CR_DATE) but much more selective index is on (CR_DATE, CR_VALUE). If I do not UPDATE any records on this table, is there any difference in INSERT operation (or another problem) when I replace actual index with multi-column index?
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Jun 17, 2010
what is the configuration dba has do for enabling the "fast-start failover concept" in the event of loss of primary database without requiring any manual steps to invoke the failover.whether the configuration are to be made in parameter file if yes what are those ?
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Sep 24, 2013
problem with populating the collection object.
I am getting an error -
'ORA-06530: Reference to uninitialized composite"
My Code is as below
create type test_t as object (empno number, ename varchar2(20))
/
create type test_tt as table of test_t
/
create or replace procedure test_p
is
[code]....
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Sep 5, 2011
I am replacing a composite PK with a new single PK as business changed. I am creating sequence to fill the new field that should present the PK but I need to fill it according to the values of the old composite PK.
CREATE TABLE ABC
(
COMP_PK1 NUMBER,
COMP_PK2 NUMBER,
COMP_PK3 VARCHAR2(8),
VAL VARCHAR2(50),
PRIMARY KEY (COMP_PK1, COMP_PK2,COMP_PK3)
);
[code].....
I need to update ABC and set ABC_SERIAL = SEQ_ABC.nextval but i need this to be done according to the order of the old composite primary key... i.e. rows with COMP_PK1 = 1 are filled before rows with COMP_PK1 = 2 and so on..
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Nov 17, 2010
understanding a redo/undo concept . Refer following data
create table t(n number);
insert into t values(10);
commit;
now I update as following
update t set n=20;
As per my understanding the before image i.e. n=10 is stored in undo (to be used for rollback, transaction recovery and even in instance recover but not in media recovery) and after image n=20 is stored in redo (to be used for various recovery purposes including media recovery in case of consistent backup).
So it is redo logs for rolling forward and undo for rolling back making transaction, db consistent . If my above understanding is true then what is meant by the term 'redo required for undo'?
Also, if there are 2 database db1 and db2 connected using database link where we are populating t1 table in db1 using t2 table in db2 using db link where redo and undo will be updated db1 or db2?
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Jul 21, 2011
How can i apply composite key on a table?
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Apr 4, 2013
write a shell script to perform impdp using dbms_datapump using SILO concept .
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Jul 3, 2013
I have a table say MY_TAB with columns as below
emp_id number,
name varchar2(30),
from_dt date,
remarks varchar2(60)
insert into MY_TAB values (1,'TOM','01-JAN-13', 'some remark');
insert into MY_TAB values (1,'TOM','02-JAN-13', 'some remark');
insert into MY_TAB values (2,'TOM','01-JAN-13', 'some remark');
insert into MY_TAB values (3,'TOM','01-JAN-13', 'some remark');
insert into MY_TAB values (4,'TOM','01-JAN-13', 'some remark');
insert into MY_TAB values (4,'TOM','02-JAN-13', 'some remark');
How do I ensure that when a user tries to insert record with emp_id as 1, then he should only be allowed to enter another from_dt but the value in the name column have to be the same as in the previous row of emp_id 1.
insert into MY_TAB values (1,'TOOM','03-JAN-13') --shld not be allowed.
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Feb 25, 2012
I need to create a composite unique index on varchar2, number and CLOB column. I haven't used such index before that have the CLOB column indexing. I found the below link related to CLOB indexing...
[URL]......
Links from where I can get related info. Also I would like to know the impact of such index on performance. I have to store and process around 50 million records in such a way, will it be beneficial to use this index?
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Jul 23, 2012
I have external file like (.csv or .txt) which contain million of record...i wnat to upload it in backend by using form 6i/10g.
by using package text_io.fopen i read it and by using for..loop conventional method insert record into table...but it will take time..
Is there any way like we use bulk collect and FORALL in backend for inserting data into table..
Is there any way to read external file at a time and insert it ...so minimize inserting time....process will become fast.
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Feb 14, 2013
I Want to tune the attached query. I have tried by creating the normal indexes and composite indexes on the fields . I feel that , Only normal index is required for this instead of composite index?
11:15:19 SQL> @slot.sql
11:16:03 SQL>
11:16:03 SQL> drop table slot purge;
Table dropped.
Elapsed: 00:00:00.05
11:16:03 SQL>
11:16:03 SQL> create table slot
11:16:03 2 (
11:16:03 3 id varchar2 (40) not null,
[code]....
- dynamic sampling used for this statement
22 rows selected.
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May 12, 2011
I have created an non unique index lk_fein on lookup_fein( code,map_id,trash). When I check the explain plan it does a full table scan on lookup_fein. if I force it to use index by it does and the cost also decreases.
SQL> SELECT WORK_FEIN,
2 NON_FEIN ,
3 FI_FEIN ,
4 MFEIN ,
5 TOTAL_FEIN ,
[code]...
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Apr 4, 2013
I am using RAC to RAC data guard environment. Os hp-unix. during primary(old standby) to standby(old primary) switchover I am ussing:
SQL>ALTER DATABASE COMMIT TO SWITCHOVER TO PHYSICAL STANDBY WITH SESSION SHUTDOWN;
I have 11.2.0.1 environment with standby and when performing switch over - it was hanging for more than 2 hours and i had to cancel it. This is what all i see in the database alert.log:
Errors in file /u02/app/oracle/diag/rdbms/drpdb/drpdb1/trace/drpdb1_m000_15160.trc:
ORA-01155: the database is being opened, closed, mounted or dismounted
Thu Apr 04 17:44:03 2013
Errors in file /u02/app/oracle/diag/rdbms/drpdb/drpdb1/trace/drpdb1_m000_15780.trc:
ORA-01155: the database is being opened, closed, mounted or dismounted
Thu Apr 04 17:59:03 2013
Errors in file /u02/app/oracle/diag/rdbms/drpdb/drpdb1/trace/drpdb1_m001_16373.trc:
[code]....
ORA-01155: the database is being opened, closed, mounted or dismounted.
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Jun 27, 2012
I am on 11.2.0.3 Enterprise Edition. We are using the new feature "Composite Domain Index" for a Domain index on a very large table (>250.000.000 rows). It really works with mixed queries. We added two number columns using FILTER BY.We have lots of DML on this table. Therefore, we are executing synchronize and optimize once the week. The synch behaves pretty normal. But "optimize_index" takes a very very long time to complete. I have switsched on 'logging' for the optimize process. The $I table takes some time but is finished normally. But the optimization of the $S table (that is the table created for the CDI feature) is running over 12 hours now - and far from being finished. From the logfile, I can see that it optimizes 1000 rows every 20 minutes. Here is the output of the logfile:
Oracle Text, 11.2.0.3.0
14:33:05 06/26/12 begin logging
14:33:05 06/26/12 event
14:33:05 06/26/12 process $N for optimize: SEQDEV.GEN_GES_DESCRIPTION_CTX_I
14:33:16 06/26/12
14:33:16 06/26/12
[code]....
I haven't found a recommendation from Oracle not to use "optimize_index" for Domain Indexes with CDI. But in my case, it would be much faster just to drop and recreate the Domain Index in question.
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Dec 20, 2011
While making a view.
1. Is it advisable to have primary key in a view.
2. Why can't we have a primary key in a view, what are its advantages. I mean one cannot search a view by index.
3. Is it because of hibernate, but again i have used distinct keyword in a view declaration which means i cannot insert via view.
Here is my code for view to make a primary key in a view.
CREATE OR REPLACE FORCE VIEW VU_NAME
PRIMARY_KEY, NAME_ID, ADDRESS_ID
)
[Code]....
alter view VU_NAME add constraint vemp_pk primary key (PRIMARY_KEY) disable
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