Composite Primary Keys
Jun 25, 2002
Newbie question...
I have two tables (categories & listings) which create a many-to-many relationship.
I have created an interim table with the primary keys from each table as a composite primary key...(cat_id & list_id).
How does the interim table get populated with the id's?
When I do an insert statement to insert data into the categories table, the cat_id field is automatically generated...same with the listings table, but when (and how) does the primary key data get into the interim table.
Thanks in advance for the assistance.
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Feb 20, 2007
Hello,
I have a table which has a composite primary key consisting of four columns, one of them being a datetime called Day.
The nice thing afaik with this composite key is that it prevents duplicate entries in the table for any given day. But the problem is probably two-fold
1. multiple columns need to be used for joins and I think this might degrade performance?
2. in client applications such as asp.net these primary keys must be sent in the query string and the query string becomes long and a little bit unmanagable.
A possible solutions I'm thinking of is dropping the existing primary key and creating a new identity column and a composite unique index on the columns from the existing composite key.
I would like to have some tips, recommendations and alternatives for what I should do in this case.
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Feb 27, 2006
Hi,
i want to make a reference from a table on itself.
The table has a composite Primary Key. But I just want to refernce the TEstCaseID.
So whats wrong? Can anyone help me?
CREATE TABLE dbo.TestCase (
Project_projectID VARCHAR(20) NOT NULL references Project,
testCaseID VARCHAR(50) NOT NULL,
PRIMARY KEY(Project_projectID, testCaseID),
FatherID VARCHAR(50) references TestCase(testCaseID)
)
THanx Crean
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Nov 23, 2006
Table 1
Code
Quarter
500002
26
500002
27
500002
28
500002
28.5
500002
29
Table 2
Code
Qtr
500002
26
500002
27
I have these two identical tables with the columns CODE & Qtr being COMPOSITE PRIMARY KEYS
Can anybody help me with how to compare the two tables to find the records not present in Table 2
That is i need this result
Code
Quarter
500002
28
500002
28.5
500002
29
I have come up with this solution
select scrip_cd,Qtr,scrip_cd+Qtr from Table1 where
scrip_cd+Qtr not in (select scrip_cd+qtr as 'con' from Table2)
i need to know if there is some other way of doing the same
Thanks in Advance
Jacx
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Aug 13, 2007
Hi,
I have recently been looking at a database and wondered if anyone can tell me what the advantages are supporting a unique collumn, which can essentially be seen as the primary key, with an identity seed integer primary key.
For example:
id [unique integer auto incremented primary key - not null],
ClientCode [unique index varchar - not null],
name [varchar null],
surname [varchar null]
isn't it just better to use ClientCode as the primary key straight of because when one references the above table, it can be done easier with the ClientCode since you dont have to do a lookup on the ClientCode everytime.
Regards
Mike
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Jan 11, 2007
Uma writes "Hi Dear,
I have A Table , Which Primary key consists of 6 columns.
total Number of Columns in the table are 16. Now i Want to Convert my Composite Primary key into simple primary key.there are already 2200 records in the table and no referential integrity (foriegn key ) exist.
may i convert Composite Primary key into simple primary key in thr table like this.
Thanks,
Uma"
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Nov 20, 2007
Apologies if this is in the wrong place..
I have been reading a bit about db design practices for SQL server and have learned how bad composite keys are!
However, I just wanted to know what the accepted alternatives are (and why they should be used);
Previously I was under the impression that adding autonumber style keys to tables are bad (extra col, doesn€™t allow unique checking of tuples). I want a table which is made up of two (single) primary keys from other tables, but the entries in the new table to be unique (and efficient). (note this is going to be part of a db which is going to grow to become very large).
Thanks,
Kenny
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Jul 30, 2007
Hi.
Could somebody please explain to me how to create a foreign key from a table that
has two composite keys? I have a table, UserPrecedence, with two composite keys -
up_owner, owner_userID. I have a second table, Users, that has the primary key
"emailAddress" and a userID table to which all other tables point their FK columns.
http://i103.photobucket.com/albums/m156/pbd22/Keys.jpg
I want the userID column in Users to be the FK of the owner_userID column in UserPrecedence
but the Modify Table view complains that "both sides of the relationship must have the
same number of columns" when I try to create the relationship.
I am guessing this is because its a composite primary key. Can somebody explain
to me how this is done correctly (and why)?
I appreciate your help.
Thanks.
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Apr 11, 2006
Hello again,
I'm going through my tables and rewriting them so that I can create relationship-based constraints and create foreign keys among my tables. I didn't have a problem with a few of the tables but I seem to have come across a slightly confusing hiccup.
Here's the query for my Classes table:
Code:
CREATE TABLE Classes
(
class_id
INT
IDENTITY
PRIMARY KEY
NOT NULL,
teacher_id
INT
NOT NULL,
class_title
VARCHAR(50)
NOT NULL,
class_grade
SMALLINT
NOT NULL
DEFAULT 6,
class_tardies
SMALLINT
NOT NULL
DEFAULT 0,
class_absences
SMALLINT
NOT NULL
DEFAULT 0,
CONSTRAINT Teacher_instructs_ClassFKIndex1 FOREIGN KEY (teacher_id)
REFERENCES Users (user_id)
)
This statement runs without problems and I Create the relationship with my Users table just fine, having renamed it to teacher_id. I have a 1:n relationship between users and tables AND an n:m relationship because a user can be a student or a teacher, the difference is one field, user_type, which denotes what type of user a person is. In any case, the relationship that's 1:n from users to classes is that of the teacher instructing the class. The problem exists when I run my query for the intermediary table between the class and the gradebook:
Code:
CREATE TABLE Classes_have_Grades
(
class_id
INT
PRIMARY KEY
NOT NULL,
teacher_id
INT
NOT NULL,
grade_id
INT
NOT NULL,
CONSTRAINT Grades_for_ClassesFKIndex1 FOREIGN KEY (grade_id)
REFERENCES Grades (grade_id),
CONSTRAINT Classes_have_gradesFKIndex2 FOREIGN KEY (class_id, teacher_id)
REFERENCES Classes (class_id, teacher_id)
)
Query Analyzer spits out: Quote: Originally Posted by Query Analyzer There are no primary or candidate keys in the referenced table 'Classes' that match the referencing column list in the foreign key 'Classes_have_gradesFKIndex2'. Now, I know in SQL Server 2000 you can only have one primary key. Does that mean I can have a multi-columned Primary key (which is in fact what I would like) or does that mean that just one field can be a primary key and that a table can have only the one primary key?
In addition, what is a "candidate" key? Will making the other fields "Candidate" keys solve my problem?
Thank you for your assistance.
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Jul 16, 2014
what the best practice is for creating indexes on columns that are foreign keys to the primary keys of other tables. For example:
[Schools] [Students]
---------------- -----------------
| SchoolId PK|<-. | StudentId PK|
| SchoolName | '--| SchoolId |
---------------- | StudentName |
-----------------
The foreign key above is as:
ALTER TABLE [Students] WITH CHECK ADD CONSTRAINT [FK_Students_Schools]
FOREIGN KEY([SchoolId]) REFERENCES [Schools] ([SchoolId])
What kind of index would ensure best performance for INSERTs/UPDATEs, so that SQL Server can most efficiently check the FK constraints? Would it be simply:
CREATE INDEX IX_Students_SchlId ON Students (SchoolId)
Or
CREATE INDEX IX_Students_SchlId ON Students (SchoolId, StudentId)
In other words, what's best practice for adding an index which best supports a Foreign Key constraint?
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Aug 31, 2007
I am trying to write triggers on each tables in my database to audit data changes. My AuditLog table consists of the following columns -
LoginName varchar(100) - user name
Action varchar(5) - this will store 'INSERT','UPDATE','DELETE'
TableName varchar(30) - name of the table updated
PrimaryKey int - primary key of the record updated
ColumnName varchar(30) - name of the column updated
OldValue varchar(1000) - old value converted to varchar
NewValue varchar(1000) - new value converted to varchar
RecUpdDate datetime - record update date.
This table design will work for tables with single column primary keys. However, it will not work for tables with composite primary keys. Any suggestions on how to make this work with composite primary keys? I prefer not to change the tables in my database to use single column primary key.
Thanks in advance.
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May 16, 2008
Pls let me know How I generate script for All primary keys and foreign keys in a table. Thereafter that can be used to add primary keys and foreign keys in another databse with same structure.
Also how I script default and other constraints of a table?
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Jul 15, 2002
Can somebody explain to me how to best do inserts where you have primary keys and foreign keys.l'm battling.
Is there an article on primary keys/Pk ?
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Mar 2, 2004
WHile designing a Database should one go for composite Primary Keys.
Or what are the Pros and Corns of Composite Primary Keys
Thanx
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Feb 24, 2014
I've been facing this situation since long but today i am asking here. Suppose i have a following tables;
AdmissionInfo, AdmID, AdmDate, AdmFee etc.
SubjectInfo i.e. SubID, SubName, SubStatus etc.
The Result table is like this:
ResID, AdmID, SubID, TheoryMarks, PracticalMarks, ObtMarks, TotalMarks, ResultTerm, SubPercentage.
ResID is PK, AdmID and SubID are Foreign Keys, right. Now What i want to ask/ learn that Am i suppose to combine ResID, AdmID and SubID as a composite PK or should i simply make the ResID as PK and other 2 be there as FK? When do we really need to use Composite PK and using it a good thing or not?
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Jul 20, 2005
i have a master table with around 15 columns and i am trying to findthe appropriate primary keys and indexes for the table.To make the records unique, i need to include two datetime columns (start and end dates ) and two integer columns ( attributes of therecord ) to make up a composite primary key. Both of these fourcolumns are found in the WHERE clause of my queries.Is it acceptable in the view of performance and how should i createthe indexes?
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Jul 3, 2006
This is really not a T_SQL question but there's no good category for it so I thought I'd just put it here.
I have a table that will contain a large amoutn of data in one field, and every piece of this data is uniquely identitied by six other attributes, that is, six other fields (e.g. user_ID, type_ID, year, country, state, item_ID). I can either make these six fields into a composite primary key, or add an additonal field (say an identity column) as the primary key and add a unique constraint on these six fields. What are the pros and cons of both designs? The one data field is of nvarchar(2000) type and the table is likely to have 50 million+ rows in a couple of years of real use.
This table is not referenced by any other tables so whatever the primary key is, there's no FK reference. However, there could be FK references to this table in the future. Does the FK possibility make a difference in the design considerations?
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Aug 4, 2007
Hello,
Does composite primary key affect performance on the table that contains the composite primary key or tables that references this table?
When composite primary key should be used?
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Feb 2, 2004
Hi
I'm trying to create a composite Primary Key on a table. This is the SQL I've written:
CREATE TABLE BookingItems
(
BookingID INT NOT NULL
REFERENCES Bookings(BookingID),
EquipmentTypeID INT NOT NULL
REFERENCES EquipmentType(EquipmentTypeID),
CONSTRAINT PK_BookingItems_id PRIMARY KEY
(BookingID, EquipmentTypeID)
)
Is this right? I'm trying to define a Primary Key made up of BookingID and EquipmentTypesID, which are both Foreign Keys as defined in the column definition.
Thanks
Jon
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Nov 27, 2007
I'm trying this
Code:
CREATE TABLE Rating
(ContentID int NOT NULL PRIMARY KEY REFERENCES Content_(ContentID),
UserID int NOT NULL PRIMARY KEY REFERENCES Usr(UserID),
rating tinyint DEFAULT 2,
LastRead smalldatetime NOT NULL DEFAULT CURRENT_TIMESTAMP)
And it is telling me this:
Msg 8110, Level 16, State 0, Line 14
Cannot add multiple PRIMARY KEY constraints to table 'Rating'.
So how do I combine two non-unique foreign keys, the combination of which is unique, into one primary key?
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Aug 23, 2004
My previous post was not really clear, so I'll try again with a (hopefully) better (even if longer) example...
Consider the following...
A JOB describes the processment of a document.
Each document can exist in two versions: English and French.
A JOB can have 1 or 2 TASK, each describing the processement of either the English or French version.
So we have the following:
A: JOB (JobNum [PK], DocReference, StartDate, EndDate, ...)
B: TASK (JobNum [PK] [FKa], Version [PK], Priority, ...)
that is there is an identifying 1:M (where maxium allowed for M is 2) relationship between JOB and TASK; TASK being identified by JobNum and Version (where the domain for Version is {E, F}).
Each TASK may require a TRANSLATION sub_task.
Each TASK may require a TYPING sub_task.
Each TASK may require a DISTRIBUTION sub_task.
For example, for a given doc, the English TASK requires TRANSLATION and DISTRIBUTION, while the French only DISTRIBUTION.
That is, there is a 1:1 not-required relationship between TASK and TRANSLATION, TYPING and DISTRIBUTION.
So we have the following:
A: JOB (JobNum [PK], DocReference, StartDate, EndDate, ...)
B: TASK (JobNum [PK] [FKa], Version [PK], Priority, ...)
C: TRANSLATION (JobNum [PK] [FKb], Version [PK] [FKb], DueDate, ...)
D: TYPING (JobNum [PK] [FKb], Version [PK] [FKb], DueDate, ...)
E: DISTRIBUTION (JobNum [PK] [FKb], Version [PK] [FKb], Copies, ...)
As you can see I am using the PK of TASK as FK and PK for each of the three SUB_TASKs.
To complicate things, each SUB_TASK has one or more assignments. The assignments for each SUB_TASK records different information from the others.
So we have...
A: JOB (JobNum [PK], DocReference, StartDate, EndDate, ...)
B: TASK (JobNum [PK] [FKa], Version [PK], Priority, ...)
C: TRANSLATION (JobNum [PK] [FKb], Version [PK] [FKb], DueDate, ...)
D: TYPING (JobNum [PK] [FKb], Version [PK] [FKb], DueDate, ...)
E: DISTRIBUTION (JobNum [PK] [FKb], Version [PK] [FKb], Copies, ...)
F: TRA_ASSIGN (JobNum [PK] [FKc], Version [PK] [FKc], Index [PK], Translator, ...)
G: TYP_ASSIGN (JobNum [PK] [FKd], Version [PK] [FKd], Index [PK], Typyst, ...)
H: REP_ASSIGN (JobNum [PK] [FKe], Version [PK] [FKe], Index [PK], Pages, ...)
that is there is an identifying 1:M relationship between each SUB_TASK and its ASSIGNMENTs, each ASSIGNMENT being identified by the SUB_TASK it belongs to and an Index.
I wish I could send a pic of the ER diagram...
Maybe there is another and better way to model this: if so, any suggestion?
Given this model, should I use for TRANSLATION, TYPING and DISTRIBUTION a surrogate key, instead of using the composite key, like for example:
C: TRANSLATION (TranslationID [PK], JobNum [FKb], Version [FKb], DueDate, ...)
D: TYPING (TypingID [PK], JobNum [FKb], Version [FKb], DueDate, ...)
E: DISTRIBUTION (DistributionID [PK], JobNum [FKb], Version [FKb], Copies, ...)
this will "improve" the ASSIGNMENTs tables:
F: TRA_ASSIGN (TranslationID [PK] [FKc], Index [PK], Translator, ...)
G: TYP_ASSIGN (TypingID [PK] [FKd], Index [PK], Typyst, ...)
H: REP_ASSIGN (DistributionID [PK] [FKe], Index [PK], Pages, ...)
I could even go further using a surrogate key even for TASK, which leads me to the following:
A: JOB (JobNum [PK], DocReference, StartDate, EndDate, ...)
B: TASK (TaskID [PK], JobNum [FKa], Version , Priority, ...)
C: TRANSLATION (TaskID [PK] [FKb], DueDate, ...)
D: TYPING (TaskID [PK] [FKb], DueDate, ...)
E: DISTRIBUTION (TaskID [PK] [FKb], Copies, ...)
F: TRA_ASSIGN (TaskID [PK] [FKc], Index [PK], Translator, ...)
G: TYP_ASSIGN (TaskID [PK] [FKd], Index [PK], Typyst, ...)
H: REP_ASSIGN (TaskID [PK] [FKe], Index [PK], Pages, ...)
I don't really like this second solution, but I'm still not sure about the first solution, the one with the surrogate key only in the SUB_TASks tables.
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Mar 21, 2007
Hi All,
I have a table that has 3 columns, two of them make a composite primary key. The table is populated with data. What I need to do is to add a third column to a composite primary key. I have tried to do that with the following command:
alter table databasesize
add constraint pk_dbsize primary key (dbid)
But I get the error message:
Table 'databasesize' already has a primary key defined on it.
How can I do this?
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Feb 8, 2008
Hi,
In my table1, I have a composite primary key ssn+firstname+lastname.
In table2 I have ssn, firstname, lastname, col1. In table2 I want to create a foreign key which references table1 primary key?
table1 and table2 has the primary, foreign key relationships. Still table2 need primary key. In table2 Can I make the ssn+Firstname+Lastname as primary key? or one column id as auto increment?
Which is best way?
Thanks
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Jul 12, 2006
Hi,
I'm currently writing a small application that is using SQL Server as a back-end database. A part of my database looks something lie the following:
Tables:
Orders(OrderId[int, PK], OrderDescription[varchar] etc...)
OrderLines(OrderId[int, PK, FK], OrderLineId[int, PK], etc...)
What I need to achieve is - everytime that a new line is inserted into an orderlines table part of the primary key will be the OrderId and the OrderLineId should be auto-incremented from 1 for each OrderId in the OrderLines table.
I know i can do this manually in my program, but i'm just wondering if theres a way to achive this in SQL Server?
Thanks,
Nick Goloborodko
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Mar 6, 2008
I have two tables: table 1 and table 2. The primary key of table is composite key of two collumns and table 2 is the child of parent table 1. Is it possible to create / define a foreign key constraint using a composite primary key?
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Jan 2, 2001
hi, can I have a composit primary key which have more than one data type. for instance job_id int,job_type varchar(20)... thanks
Al
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Sep 19, 2000
Hi,
I have a doubt, can anyone please clarify me.
I have created the following table,
create table z
(
eno int,
deptno char(2),
ename varchar(5),
constraint pk_eno_deptno primary Key(eno,deptno)
)
and I tried to establish a foreign key based on the above defined table. It's giving error,
create table z_dup
(
eno int FOREIGN KEY REFERENCES z(eno),
deptno char(2)
)
go
Error:-
*****
There are no primary or candidate keys in the referenced table 'z' that match the referencing column list in the foreign key 'FK__z_dup__eno__18CE1BA6'.Could not create constraint. See previous errors.
Even I tried to create a foreign key like the following,
create table z_dup
(
eno int FOREIGN KEY REFERENCES z(eno,deptno),
deptno char(2)
)
go
Error:-
********
More than one key specified in column level FOREIGN KEY constraint, table 'z_dup'.
Can anyone please help me to create a foreign key relation with the base table.
tks in advance,
Srinivasan
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Jul 24, 2014
I am trying to create a FK using a composite PK and here are the details that I want to achieve.
Table -A
Column A1 not null,
Column A2 not null
Primary key (A1, A2).
Table -B
Column B1 Primary key.
Column B2 not null
FK (B2) References A(A1).
When I try to do this I am getting some errors. Questions: First of all is this possible? if yes, then how I can create it.
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Mar 26, 2008
NOTE:
I am not interested in any responses that want to argue the use of a unique ID field and autonumbering as the PK. It is quite clear from the forums that this subject is a polarizing one. This question is for those who follow text-book design practices and believe that a composite primary key should be used when it is available. I want to be one of them for the time being.
SYNOPSIS:
I have three tables, TestSummary, TestDetails, and Steps.
The TestSummary table looks like this:
Create table TestSummary
(
TestSummaryID int identity primary key,
...
SequenceID int not null
)
It contains the date and time of the test, the serial number, the part number, the test operator's name, and the ID of the sequence of steps used during the test. It uses a unique ID field for the primary key.
The TestDetails table looks like this:
Create table TestDetails
(
TestDetailsID int identity primary key,
TestSummaryID int not null,
StepID int not null,
...
)
It contains the details of the test like voltage readings, current readings, temperature, etc., one record per reading. It also contains the step number of the test sequence specified in the TestSummary table.
The Steps table looks like this:
Create table Steps
(
SequenceID int not null,
StepID int not null,
Function int not null
Primary key (SequenceID, StepID)
)
It contains a list of all of the functions to be performed on the device under test by sequence number and the step number within the sequence.
When I try to establish a relation between TestSummary.SequenceID and Steps.SequenceID, SQL Server flags an error because TestSummary.SequenceID and Steps.SequenceID:Steps.StepID do not match.
What is the problem with this approach?
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Jul 23, 2005
Is that possible on SQL Server 2000 and onwards?
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Jul 20, 2005
Is is possible to create a composite primary key on a table variable?Neither of these two statements are successful:DECLARE @opmcjf TABLE (jobdetailid INT NOT NULL,cjfid INT NOT NULL,cjfvalue VARCHAR(100) NULL)ALTER TABLE @opmcjf ADD CONSTRAINT [PK_opmcjf] PRIMARY KEY CLUSTERED([jobdetailid],[cjfid])andDECLARE @opmcjf TABLE (jobdetailid INT PRIMARY KEY,cjfid INT PRIMARY KEY,cjfvalue VARCHAR(100) NULL)Thanks,Shaun
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Sep 1, 2006
Hi ,
We have scenario like this .the source table have composite primary key columns c1,c2,c3,c4.c5,c6 .when we move the records to destination .we have to check columns (c1+ c2 + c3 + c4 + c5 + c6) combination exist in the destination. if the combination exist then we should do a update else we need to do a Insert . how to achive this .we have tryed useing conditional split which is working only for a single Primary key . can any one help us .
Jegan.T
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Jan 24, 2008
I want to created composite primary key using MS SQL Server Enterprise Manager Interface. I want to use Interface instead of writing it in CREATE Table statement. I was able to create foreign key using this Interface using the "Manage Relationship" option. But cannot find how to add primary key consisting of two fields. Any help regarding this is highly appreciated.
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