Transact SQL :: Size Of Foreign Keys In Server 2012?
Jun 30, 2015I have question about the size of foreign key’s in sql-server 2012. If I in one table had a foreign key of the “INT” type. Do it still cost 4 bytes of storage?
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Transact SQL :: What Is Advantage Of Foreign Keys In Database
Apr 22, 2015suppose if we do not have FK then what kind of advantage we could not avail. we can fetch data from two table by creating a relation in sql.....then why FK is required.
View 10 Replies View RelatedTransact SQL :: Identify Primary And Foreign Keys In Two Table
Apr 23, 2015I've attempted to identify a primary and foreign key in these two tables, but I am getting a bunch of errors re duplicate keys and column names needing to be unique.Perhaps the primary and foreign key I have identified don't meet the criteria?
CREATE TABLE StockNames
(
-- Added Primary key to [stock_symbol]
[stock_symbol] VARCHAR(5) NOT NULL CONSTRAINT PK_stock_symbol PRIMARY KEY,
[stock_name] VARCHAR(150) NOT NULL,
[stock_exchange] VARCHAR(50) NOT NULL,
[code].....
Transact SQL :: Left Join To Get Info From A Table With Foreign Keys
Sep 13, 2015I am still new to SQL and I am having trouble obtaining the results I need from a query. I have worked on this command for some time and searched the internet but cannot seem to still get it correct.
I have a table called Patient. It's primary key is pat_id.
I have a second table called Coverage. It has no primary key. The foreign keys are pat_id, coverage_plan_id, and hosp_status.
I have a third table called Coverage_History. It has a primary key consisting of pat_id, hosp_status, copay_priority, and effective_from.
I want to get the pat_id and all the coverage information that is current. The coverage table contains specific insurance policy information. The coverage_history table will indicate the effective dates for the coverage. So the tables could contain something like this:
Patient (pat_id and lname)
P123 Monto
P124 Minto
P125 Dento
P126 Donto
Coverage (pat_id, coverage_plan_id, hosp_status, policy_num)
P123 MED1 OP A1499
P123 ACT4 OP H39B
P124 MED1 OP C90009
P124 RAC OP 99KKKK
P124 RAC OP 99KKKK
P124 MED1 OP C90009
P125 ARP OP G190
P126 BCB OP H88
Coverage_History (pat_id, hosp_status, copay_priority, effective_from, coverage_plan_id, effective_to)
P123 OP 1 20150102 MED1 NULL
P123 OP 2 20150102 ACT4 NULL
P124 OP 1 20150203 RAC 20150430
P124 OP 2 20150203 MED1 20150430
P124 OP 1 20150501 MED1 NULL
P124 OP 2 20150501 RAC NULL
P125 OP 1 20150801 ARP NULL
P126 OP 1 20150801 BCB 20160101
select p.pat_id, p.lname, ch.coverage_plan_id, ch.hosp_status, ch.effective_from, ch.effective_to, ch.copay_priority,
from patient p
left join
( coverage_history ch left join coverage c on ch.coverage_plan_id = c.coverage_plan_id and ch.patient_id = c.patient_id and
(ch.effective_to is NULL or ch.effective_to >= getdate()
)
) on ch.patient_id = p.patient_id
where ( ch.effective_to is NULL or ch.effective_to >= getdate() )
So I want to see:
P123 Monto MED1 OP 20150102 NULL 1
P123 Monto ACT4 OP 20150102 NULL 2
P124 Minto MED1 OP 20150501 NULL 1
P124 Minto RAC OP 20150501 NULL 2
P125 Dento ARP OP 20150801 NULL 1
P126 Donto BCB OP 20150801 20160101 1
Transact SQL :: How To Apply Foreign Keys On Top Of A Common Lookup Table
Apr 29, 2015I have an issue where i am mandated to enforce RI on an applications database (a good thing). but I have several common lookup tables where many of the "codes" reside for many different code types. I also have the mandate that i cannot change the underlying DDL to make composite keys to match the codes table PK. I am currently looking at creating indexed views on top of the Codes table to seperate the logical tables it contains. This is several hundred views.
I do know that I do not want to write several hundred triggers to enforce RI. Table schema below, the CdValue column is the column that is used throughout the hundreds of tables that use this codes table, and their corresponding column is not named the same.
CREATE TABLE dbo.CodesTable (
PartyGrpId INT NOT NULL
, CdTyp VARCHAR ( 8 ) NOT NULL
, CompId INT NOT NULL
, CdValue VARCHAR ( 8 ) NOT NULL
, CdValueDesc VARCHAR ( 255 ) NULL
, AltValueDesc VARCHAR ( 100 ) NULL
[Code] ....
I did though run into one forum where a person brought up a great idea. Filtered Foreign Keys, what a novel concept, if it could work it would make so much less code to fix an issue like this.
ALTER TABLE dbo.BusinessStatus WITH NOCHECK
ADD CONSTRAINT FK_dbo_BusinessStatus_CodesTable FOREIGN KEY (LoanStsDtCd) REFERENCES dbo.CodesTable (CdValue) WHERE CdTyp = 'Status'
SQL 2012 :: Get Order In Which Foreign Keys Are Applied
Sep 10, 2015Probably not the best "Subject Title", but no the less what I am looking for is a way to get the order in which I should insert data into a table that has 10 FK's to it. I have queries that list them out for me, but they do that in what seems to be alphabetical order. You can also right click the table in question and select view dependencies, but that as well appears to be in alphabetical order.
Is there any query or any way to see what order I should be inserting and/or deleting data into FK tables?
SQL 2012 :: Explicit Columns Or NULL Foreign Keys?
Mar 19, 2014I have a table called Appointment, for storing (you guessed it) appointments at a medical practice. If an appointment is cancelled, I want to collect a cancellation reason, so let's say that I create a second table called Cancellation which has a foreign key relating to the Appointment table's primary key, AppointmentID, and another column, Reason. Now, in order to indicate that an appointment was cancelled, I could include a Cancelled column in the Appointment table with a bit datatype, or instead I could infer that an appointment must be cancelled if it has a corresponding record in the Cancellation table.
It may be that it'd be better to store the cancellation reason in the Appointment table - But regardless, let's say I stick with the two-table solution described above, and I subsequently want to write a query to list all appointments which have been cancelled. If I had the Cancelled column in the Appointment table, I could simply query for all records in that table where that column's value was FALSE. If I went the other way and DIDN'T have a Cancelled column, I could instead write a query joining the Appointment and Cancellation tables to return all records in Appointment with a corresponding record in Cancellation.
That latter method, whilst slightly more complicated because it involves joining two tables, seems to me to be the most normalised. Instead of storing the fact that an appointment is cancelled in two different tables, that fact is only stored in the Cancellation table. Would there be a performance hit in using the two-table, 'inferred cancellation' method rather than just having a bit column in the Appointment table? Would that performance hit be enough to persuade you to use a Cancellation column in the Appointment table instead? And what about if I were to apply that method to other things associated with each appointment, e.g. Is it completed? Is it chargeable to the client or an insurance company? Is the client and in-patient or out-patient?
SQL 2012 :: Create Table With Both Keys As Foreign (error)
Dec 15, 2014I'm trying to create a table in Microsoft Server Management Studio 2012. The table has two fields which are both foreign keys.
I created the following:
create table tblRoomEquipment(
RoomID nvarchar(8),
EquipmentType nvarchar(1),
foreign key (RoomID) references tblRoom(ID),
foreign key (EquipmentType) references tblEquipment(Type)
)
Both tblRoom and tblEquipment have the red line error which when I highlight say the they both reference an invalid table!
Both tables are there and have primary keys defined as ID & Type. I have searched around and all I could find was that there maybe a permission problem.
Creating Inter-table Relationships Using Primary Keys/Foreign Keys Problem
Apr 11, 2006Hello 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.
Creating Indexes On Columns That Are Foreign Keys To Primary Keys Of Other Tables
Jul 16, 2014what 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?
Foreign Keys - On Which Kind Of Keys Do The Base On?
Nov 22, 2007Hello!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
View 6 Replies View RelatedTransact SQL :: 2012 / Insert Foreign Key Value Into Primary Table?
Oct 2, 2015In a special request run, I need to update locker and lock tables in a sql server 2012 database, I have the following 2 table definitions:
CREATE TABLE [dbo].[Locker](
[lockerID] [int] IDENTITY(1,1) NOT NULL,
[schoolID] [int] NOT NULL,
[number] [varchar](10) NOT NULL,
[lockID] [int] NULL
CONSTRAINT [PK_Locker] PRIMARY KEY NONCLUSTERED
[Code] ....
The locker table is the main table and the lock table is the secondary table. I need to add 500 new locker numbers that the user has given to me to place in the locker table and is uniquely defined by LockerID. I also need to add 500 new rows to the corresponding lock table that is uniquely defined in the lock table and identified by the lockid.
Since lockid is a key value in the lock table and is uniquely defined in the locker table, I would like to know how to update the lock table with the 500 new rows. I would then like to take value of lockid (from lock table for the 500 new rows that were created) and uniquely place those 500 lockids uniquely into the 500 rows that were created for the lock table.
I have sql that looks like the following so far:
declare @SchoolID int = 999
insert into test.dbo.Locker ( [schoolID], [number])
select distinct LKR.schoolID, A.lockerNumber
FROM [InputTable] A
JOIN test.dbo.School SCH ON A.schoolnumber = SCH.type and A.schoolnumber = @SchoolNumber
JOIN test.dbo.Locker LKR ON SCH.schoolID = LKR.schoolID
AND A.lockerNumber not in (select number from test.dbo.Locker where schoolID = @SchoolID)
order by LKR.schoolID, A.lockerNumber
I am not certain how to complete the rest of the task of placing lockerid uniquely into lock and locker tables? Thus can you either modify the sql that I just listed above and/or come up with some new sql that will show me how to accomplish my goal?
SQL Server, Master Detail Without Foreign Keys
Mar 27, 2007As part of a project, I'm not allowed to use foreign keys, well can't. But I have a problem with this master detail relationship (and a very simple one too).
Tables to begin with:
Invoice:
invoiceid : bigint indentity autoincrement primarykey
Detail:
invoiceid: bigint - detailnumber:bigint - desc : char20
Okay - I want to set these two tables up such than when I create a new invoice, and subsequently get the new invoiceid, and I start to add detail records to the detail table, I want the detailnumber to autoincrement when I do an SQL Insert. Right now I have detailnumber as the primary key, so when you view the detail records, it looks like:
(invoiceid, detailnumber, desc) 1,1,text - 1,2,text - 1,3,text - 2,4, text on another invoice - 3,5, text
I want it to work like:
(invoiceid, detailnumber, desc) 1,1,text - 1,2,text - 1,3,text - 2,1, text on another invoice - 3,1, text
where the invoiceid and the detail number make up the primary key.
I seem to recall you could do this is PHP before it had foreign keys & such, and I'm completely drawing a blank on this. BTW - I'm using enterprise manager to set this up, but I can use QA with a sample script to acheive the same.
I realize this may be (and probably is) off-topic here, but I can't figure out where to ask.
Thanks in advance.
Foreign Keys In Server Management Studio
Jan 25, 2008I think I did this before but how do you designate foreign keys in SQL Server Management Studio?
View 2 Replies View RelatedDB Design :: Extracting Relationships From FoxPro Code And Generate Foreign Keys In Server
Aug 4, 2015I have taken on a contract to improve reporting for an old HR database that was developed using FoxPro (Visual FoxPro, I think) with the data stored in SQL Server 2000. There are no foreign keys in SQL Server 2000 so the relationships are maintained inside FoxPro.Is there a way of extracting the relationships from the FoxPro code and generate foreign keys in SQL Server, so that I can do proper design?
View 7 Replies View RelatedForeign Keys
Apr 17, 2007Can any body tell me how to know to what columns of other table it refers to.
shiva kumar
Foreign Keys
Aug 24, 1999Could someone enlighten me as to the advantage of using the foreign key tab when in table design mode in the Enterprise Manager. Does it have any advantages ?? Is it necessary ??
thanks in advance
Paul
Foreign Keys
Mar 29, 2001I haven't tried, but does anyone know if its possible to a have a foreign key for two tables when the tables reside in different databases (on the same server)?
Thanks,
Doug Smith
Foreign Keys
Oct 25, 2001l'm trying to do inserts on tables with foreign keys and they keep crashing. Can somebody please help.Whats the best way of populating data that has foreign keys?
View 1 Replies View RelatedForeign Keys
Oct 4, 2004How would I drop a foreign Key?
Thanks
Lystra
Keys, Foreign Key?
Mar 10, 2004I need to know if this is required? I have products, with the help of their business account numbers, are naturally categorized numerically. I want to create a product category table and a product account table.
Example :
tbProductCategories
TypeCode | Description
1000 | Cups
2000 | Plates
tbProductAccounts
Account | Description
1001 | Mug
1002 | Glass
2001 | Plate
2002 | Saucer
With the above tables (which are made up :) ), would you include
a foreign key in tbProductAccounts indicating the type code?
What would the stored proc look like without it?
Create Procedure usp_GetProductAccounts
@iTypeCode int
AS
SELECT tbProductAccounts.Account,
tbProductAccounts.Description
FROM tbProductAccounts
WHERE tbProductAccounts.Account - iTypeCode > 0 AND < 999
Would this work? Or should the foriegn key always be included?
Mike B
Foreign Keys - Allow Zero?
Jun 8, 2008I am creating a series of foreign keys in my new database, and so far everything is going fine. The company I work for never uses them, and I am working on my own stuff on my own time now.
I come across one table that I do want one field to allow zeroes, but when its set to a value, to exist in the other table.
To be more specific. I have a PO type table, which has an EmployeeID of the person who made the PO, and another field to store who received the PO when the order arrives. I want that 2nd Employee field to be zero until it's received.
I created an employee of zero, to allow the foreign key to be created. But all the other tables that have foreign keys to my Employee table I would prefer to not allow zeroes. So I changed them to use a check of (employeeid > 0).
Is it possible to have a foreign key say that I want the value from the Field in Table A to exist in table B, or to be zero? Or would it just be easier to leave off the foreign key in this one case?
Tks
Foreign Keys
Dec 15, 2006Shiry writes "Hi, I'm a beginner and I'm a bit stuck here..
I'm creating this database for my homework, I'm using Marks & Spencer as an
example. It has a table, products, for the clothes
id
name
cat_id ....... connected to typ_cat
colour_id ...... connected to typ_colour
size_id ....... connected to typ_size
price
sup_id ....... connected to typ_sup ...... but here i'm stuck a bit, are you
allowed to connect a typ_table to another typ_table?
this is the typ_sup:
id
name
address
city_id ......... connected to typ_city
or rather have a separate sup table with the same id, name, address, city_id
id will be connected to typ_sup
and the products table.. sup_id will then be connected to typ_sup..?
What way is better? and is it allowed to connect a typ_table to another
typ_table?
Thanks in advance!!!!
Shiry"
Foreign Keys
Oct 11, 2006I have created two tables:
UserInfo:
UserID (PK)
Hairid
eyeColorid
faceShapeid
and
HairInfo:
HairInfoID (PK)
Hairid
HairDesc
Now I want to have a one to many relationship between UserInfo and HairInfo. I want to specify Hairid as the foreign key in the HairInfo table. Here UserInfo is the parent and HairInfo is the child. I am using SQL server 2000. Is there a way to do it using the Enterprise manager interface. Can someone run me through the steps to do it.
Thanks...
Set-Off Foreign Keys
Feb 28, 2008Is there a way to temporaly set off foreign keys dependencies (like a sql command or something...) and then set them on again? I've to migrate 90 tables on my app, but i get the "dependencies error", any ideas?
View 4 Replies View RelatedUse Of Foreign Keys
Mar 24, 2008having been used to creating databases for the past nine years in MS Access, i have been recently getting used to the basics of SQL Server 2005 express edition. i know pretty much all of the simple basics, but i have hit some trouble.
in MS Access, when i have used the "Design View" to develop all of my tables, fields and validation rules, i have used their "Lookup Wizard" to develop ways of assigning a record to a certain value - example;
CLUB:
Club_Id (Primary Key)
Club
PLAYER:
Player_Id
Player_Name
Club (Foreign Key)
the flaw, i suppose, is the ease with which i can create a relationship between TWO tables without the child tables foreign key having to be an ID (integer) and users can select a "Club" of their choice to assign a "Player" to in the PLAYER table. i.e.
CLUB:
Club_Id: 1
Club: Man Utd
PLAYER:
Player_Id: 1
Player_Name: Ryan Giggs
Club: Man Utd (FKEY)
instead of;
PLAYER:
Player_Id: 1
Player_Name: Ryan Giggs
Club: 1 (FKEY)
i hope i am making sense. now the awkward bit as far as i'm concerned:
in SQL Server 2005 Management Studio Express, i cannot do this once i do the necessary tables, content and relational diagrams.
so i have this;
PLAYER:
Player_Id: 1
Player_Name: Ryan Giggs
Club: 1 (FKEY)
instead of what i want, which is this;
PLAYER:
Player_Id: 1
Player_Name: Ryan Giggs
Club: Man Utd (FKEY)
how can this be achievable using Studio Management Express 2005 for someone like myself who is still something of an SQL novice (of a sort)
help would be much appreciated
Remote Foreign Keys
Jun 21, 2007Right now i'm building a language centre DB. Is going to hold translations for data in tables in another DB (english DB). The idea is going to be that there is going to be a table in the Language DB for every language and table it is going to translate in the english DB.
So lets consider the following in the English DB:
PROJ_TBL_HELPTOPICS -> PK_HELP_ID -> TITLE -> DESCR
PROJ_TBL_CATEGORIES -> PK_CAT_ID -> TITLE -> DESCR
In the Language DB I want to hold translations for HELPPTOPICS and CATEGORIES, and I want translations for Spanish and Japanese.
PROJ_TBL_HELPTOPICS_ES -> PK_TRANS_ID -> FK_HELP_ID -> TRANS_TITLE -> TRANS_DESCR
The rest is going to be the layout as abovePROJ_TBL_HELPTOPICS_JA PROJ_TBL_CATEGORIES_ESPROJ_TBL_CATEGORIES_JA
The reasons I separated up the language DB from the english DB are:
1. English DB has, and is going to have a lot more tables, and is going to be heavily queried (plus I think dont think the translations are going to be used anywhere near as often and the english). I figured the less tables, where possible, the better.
2. Putting translations in different a different DB, I could take better advantage of colliations specific to a language for example when using Full-Text searching on Japanese text
Anyways, here's my question!?!
I want to link the foreign key column to the table it is translating primary key column (in the English DB). I want to be able to take advantage of Cascade on Delete. So when an item is deleted from EnglishDB.PROJ_HELP_TOPICS it is going to be deleted from LanguageDB.PROJ_HELP_TOPICS_[LANG ISO]. Is this done through Mirroring?
Help On Foreign Keys And Tables
Jan 7, 2008hi.
How to update FormA table from customer table. Let say i wish to keep small number of fields from each table so i use foreign keys as reference.
However i had a problem when i tried to save the relationships of both tables, i receive the error that FormA_id is not able to insert null into value.
Cust_id(PK) is identify column, as well FormA_id(FK) and FormA_id(PK) too. For example, when i insert a record from customer table, it will automatically create id for FormA.
Table structure. Customer
cust_id(PK),name,age,formA_id(FK)
Table structure, FormA
formA_id(PK), info, date,
How to solve ?
Help With Deleting And Foreign Keys.
Feb 3, 2008I'm working with a SQL 2000 DB, which has a table structure as follows, implemented with foreign key constraints: ________________________________| ||--> TABLE1 --> TABLE2 --> TABLE3 --|
(ie, it forms a 'loop' so to speak)
I am trying to create a clean copy of this database, basically by deleting all the data in most of the tables, and these 3 tables are included. Of course, when I run a DELETE on any of these tables, it complains because of the FK. How can I script a delete on the 3 tables without manually deleting row after row, until there aren't anymore relations?
Cheers for any help :)
Removing Foreign Keys
Feb 1, 2004Hi everyone,
I've been using VS.NET to design and implement my SQL databases. This has been simple and effective.
I've deployed the database onto the production database server and it's been performing without a hitch for some time now.
My problem is that I now need to remove a foreign key relationship on the production database as I have had a relationship between two tables but now not wanting the relationship since the data that had the relationship is now not wanting to be compulsory. I've had a look in the system.foreignkey (I think) table but I can't make head or tail of it.
Long story short, how can I find and remove the relationship from Query Analyser / Enterprise Manager ? I know how to do this in VS.NET diagram (just delete the relationship) but when you open the production database in VS.NET the diagram is no longer there.
Any help will be appreciated!!
Thanks!
Andrew
Novice Needs Some Help With Foreign Keys
Sep 4, 2005Hey all - been knocking my head on this on for awhile - perhaps someone could shed a little light.
I have 2 tables that I want to link:
Table 1:
UserID - Primary key
First Name
Last name
AuditionID - FK
Table 2:
AuditionID - PK
Description
Sing
instrument
So - I have a web form that collects the information for both tables and then insets the collected data. But, the AuditionID value in Table1 does not update. Now, I assume I am incorrect in thinking the AuditionID in Table1 will be automagically updated when Table2 creates it's key...?
If that is indeed the case, how do you update 2 tables and maintain a foreign key relationship?
I hope I am being clear enough - any help would be greatly appreciated.
Thanks all
Triggers And Foreign Keys
Aug 25, 1998Hi!
Does anybody know why after applying both triggers and foreign keys to a table (standard relational database procedure!!!), when I try to perform, say a simple delete, I am not allowed to do so and get this error message:
Msg 547, Level 16, State 2
DELETE statement conflicted with COLUMN REFERENCE constraint `FK_contract_1__14`. The conflict occurred in database `tmp`, table `contract`, column `employee_id`
Command has been aborted.
HELP!!!!
Cheers, Marc
Foreign Keys For Some Rows, Not Others
Jan 14, 2005I have a database with a set of items that have different ways of describing their locations. One type of item uses states, the other uses some arbitrary region that could cross state boundries. Every item in each state/region is numbered starting at 1, so that each item within a state/region has a unique area number.
So I have a table of states (that doesn't need maintaining) and a table of regions (that does. New regions could be added, existing regions could be modified.)
CREATE TABLE states (
stateId int primary key,
stateCode char(2),
stateName varchar(16),
UNIQUE(stateCode)
)
CREATE TABLE regions (
regionId int primary key,
regionCode char(6),
regionName varchar(32),
UNIQUE(regionCode)
)
My table of items points to these other tables. I want to use foreign keys for referential integrity. So my table looks something like this:
CREATE TABLE items (
itemId int primary key,
itemName varchar(32),
itemType ENUM('state', 'region'),
areaNum int,
stateId int NULL,
regionId int NULL,
UNIQUE(itemName),
UNIQUE(areaNum, stateId, regionId),
FOREIGN KEY stateId REFERENCES states (stateId),
FOREIGN KEY regionId REFERENCE regions (regionId)
)
My problem seems to be that when I insert records into the items table, MS SQL doesn't like a foreign key entry to be null (even though I say it can be null.) I think the problem is that there is no value in the states or regions table with the stateId/regionId = 0. I don't want to entry a dummy entry for a non-state or non-region, but I can't figure out how to do this otherwise.
Is there a way to have MS SQL permit a foreign key value to be NULL? Or is there a better way to organize this data? I would appreciate any guidance. Thanks.