Alternative To Composite Keys..
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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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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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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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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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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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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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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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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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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Nov 22, 2007
Hello!I have a table A with fields id,startdate and other fields. id and startdateare in the primary key.In the table B I want to introduce a Foreign key to field id of table A.Is this possible? If yes, which kind of key I have to build in table A?Thx in advance,Fritz
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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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Sep 23, 2006
I'm just now learning both SQL and ASP.NET, and I cannot seem to figure out how to build my data structure. I believe the answer to my problem is a composite key, but I cannot seem to get it to work. Here is an example. My database is of recorded dances, with exact locations within a ballroom. I believe I need 2 tablesTable #1 - DanceTableColumns: DanceID, Name, Description, TagsTable #2 - StepsTableColumns DanceID, StepID, longLocation, latLocation, Action, DescriptionWithin my ASP.NET application I want to be able to enter data about a dance, including metadata and a series of steps. The Dance and metadata content to be stored in DanceTable, and the series of moves stored in the StepsTable. I want the steps to be IDed as 1, 2, 3, 4...x with the first step being labled 1. and I want each dance to have it's own unique ID (DanceID). Right now I'm using "ExecuteNonQuery()" to add my data to my SQL database, and when I add new steps to the StepsTable SQL just finds the largest ID within StepID and increments it by one. So my steps are labeled as:Dance1:Step1, Step2, Step3, Step4Dance2:Step5, Step 6, Step7What I really want is (or I think what I want is) is a composite primary key.Dance1:Step1, Step2, Step3, Step4Dance2:Step1, Step2, Step3That way the StepID is used as both a primary key and it indicates the position within the dance. I guess I could just use a standard SQL table, let SQL auto generate StepID's and then add a new column called something like "StepNumber", but it just seems goofy to be generating a stepID and never using it. With composite keys (If I understand them) each step would have a unique key as a combination of the DanceID+StepID (AKA Dance 345, steps 1-10). I pull up data by searching for dances, and then sort by StepNumber, and those should all be unique...if I can figure out how to build them.
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Nov 9, 2006
I have a table with a composite key formed by the unique combination of columns w, x, y, z
I'm trying to write an INSERT statement along the following lines
INSERT INTO myTable
(SELECT w, x, y, z FROM someTable) t1
WHERE (this is the part I'm stumped on - where the unique combination of w, x, y, z is NOT in myTable already)
Help would be appreciated. Can you use the NOT IN keyword on composite values?
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May 29, 2008
How can I create a composite key (two primary keys for one table) using SQL Server 2005 Management Studio? Can I do it using the GUI, or do I have to write SQL code to do this? Thanks
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Apr 19, 2004
Made an interesting discovery today - a column of data type Bit is not allowed to participate in composite key. Rather surprised.
I have a certain unique code that exhibits 2 unique states, which rendered the use of the boolean column, so the uniqueness goes <code>-1 and <code>-0. Is there any 'hack' so to speak to avoid using a Tinyint for the boolean column instead?
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Jun 10, 2005
Hi,
Suppose there is a composite index on a table, and in includes, for example 3 columns.
If I do a select using one of those three columns, will the select use the composite index? Will it aid in retrevial or should I create an index on the
individual column.
any thoughts on this would be appreciated.
thanks
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Sep 24, 2004
Can someone help me create a composite key on ms sql server through the enterprise manager?
Thanks,
Laura
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Aug 21, 2004
The orininal design of my db (part of it...) is the following
A JOB has a Number and a Description.
Each JOB can have one or two TASKS (min one, max two). Each TASK is identified by the JOB it belongs to and an Index (unique only for the same JOB).
Each TASK has one an only one set of INFO1, one and only one set of INFO2, one and only one set of INFO3 etc.
A: JOB (JobNum [PK], JobDescription, ...)
B: TASK (JobNum [PK] [FKa], Index [PK], TaskDescription, ...)
C: INFO1 (JobNum [PK] [FKb], Index [PK] [FKb], ...)
D: INFO2 (JobNum [PK] [FKb], Index [PK] [FKb], ...)
(There is a reason to keep INFO1, 2 and 3 separate, because eachof them will be linked to different table. This might influence the answer to my real question.)
First of all, I wouldn't add any surrogate key for TASK, not to loose the logic behind; plus I'd put an ined on JonMum only, being Index equal to 1 or 2 only, so not selective.
The real question is about INFO1 (and 2, 3 etc.) table: should I leave JobNum and Index as PK (consider that the PK of INFo1 will be used as FK for another table), or should I use a surrogate key, like for eaxmple
C: INFO1 (Info1ID [PK], JobNum [FKb], Index [FKb], ...)
I don't really like this solution. Actually I'd prefer the following
C: INFO1 (Info1ID [PK], ...)
where Info1ID = JobNum + Index (+ = string concatenation).
Any suggestion?
Thanks
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Feb 11, 2005
Hi folks, i need an advise.
I've a gerand table customers_orders table with customer_id and order_id.
Whenever we have to find orders, for customer, this table is involved. Hey; i know u'll be angry y the heck this gerand exist but i've to blame the older dudes then.
Now this table has composite clustered index; CUSTOMER_ID+ORDER_ID.
The tables have grown over GB size; i see HASH INNER JOIN rather than MERGE for the GEREND and CUSTOMER table join.
Is it good to use composite clustered index; or should i clustered one the columns in the GEREND and other to normal index. What performance impact it could be.
Howdy!
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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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May 11, 2004
Hello, everyone:
I need to define composite PK and FK for a ERD. Could someone offer the methods that work with,
1. T-SQL
2. ERD
Thanks a lot.
ZYT
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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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Jul 30, 2007
Hi,
i am using the DTC in my code to connect to two different servers on the network through a SQL query which is unfortunately very slow; can u please guide me with an alternative for the same
Thanks
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Jul 20, 2005
SELECT *FROM organizationWHERE (departmentID = divisionID) AND (divisionID = branchID) AND(branchID = sectionID) AND (sectionID = unitID)Is there anyway I can make this query more simlified w/o repeating thesame column in the where clause?thankss/RC
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Nov 24, 2006
The table above is my users table. It allows for a user to be at multiple sites or multiple locations within a single site or multiple sites. Would it be wise to use a auto incrementing primary key instead of the 3 column composite key? The reason I ask is because if I am referencing this SU table (which I will be a lot), a lot more data would be replicated to the tables which have the foreign key to this table, right? But if I used a single incrementing column as the primary key, only a small integer would be used as the foreign key, saving space?Does this make sense?
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Oct 29, 2007
Hi All, Can anyone tell me how to create a reference for composite key. For ex, I have created tblEmp table successfully. create tblEmp( empId varchar(100), RegId varchar(100), empname varchar(100),constraint pk_addprimary key(empId, RegId) ) And now, I am going to create another table which references the composite key.create table tblAccount( acctId varchar(100) primary key, empId varchar(100) references tblEmp(empId), RegId varchar(100) references tblEmp(RegId) ) But it gives error like Server: Msg 1776, Level 16, State 1, Line 1There are no primary or candidate keys in the referenced table 'tblEmp' that match the referencing column list in the foreign key 'FK__tbl'.Server: Msg 1750, Level 16, State 1, Line 1Could not create constraint. See previous errors. Could anyone please let me know how to create reference for composite key. Thanks in advance,Arun.
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Jun 6, 2008
Hi What is the difference between Candidate key , composite key and alternate key. I went through many websites but I didn't get examples. There were only definitions. Can anyone please tell me the site or blogs that elaborate this concept RegardsKaran
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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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