Are Foreign Keys in SQL Server 2008 are automatically indexed with a value? For Example. if I add a value in my Primary key (or auto incremetend) in may parent table will the table that has a foreign key referenced to that key will automatically have the same value? or I Have to do it explicitly?
No, if you create a foreign key in a child table, it will not automatically get populated when a parent row gets inserted. If you think about this it makes sense. Let's say you have a table like:
CREATE TABLE dbo.Students
(
StudentID INT IDENTITY(1,1) PRIMARY KEY,
Name SYSNAME
);
CREATE TABLE dbo.StudentLoans
(
LoanID INT IDENTITY(1,1) PRIMARY KEY,
StudentID INT FOREIGN KEY REFERENCES dbo.Students(StudentID),
Amount BIGINT -- just being funny
);
What you are suggesting is that when you add a row to Students, the system should automatically add a row to StudentLoans - but what if that student doesn't have a loan? If the student does have a loan, what should the amount be? Should the system pick a random number?
Typically what will happen in this scenario is that you'll be adding a student and their loan at the same time. So if you know the loan amount and the student's name, you can say:
DECLARE
#Name SYSNAME = N'user962206',
#LoanAmount BIGINT = 50000,
#StudentID INT;
INSERT dbo.Students(Name)
SELECT #Name;
SELECT #StudentID = SCOPE_IDENTITY();
INSERT dbo.StudentLoans(StudentID, Amount)
SELECT #StudentID, #LoanAmount;
Related
I'm doing a school project about a school theme where I need to create some tables for Students, Classes, Programmes...
I want to add a Group to determined classes with an auto increment in group_id however I wanted the group_id variable to reset if I change any of those attributes(Classes_id,courses_acronym,year_Semesters) how can I reset it every time any of those change??
Here is my table:
CREATE TABLE Classes_Groups(
Classes_id varchar(2),
Group_id INT IDENTITY(1,1),
courses_acronym varchar(4),
year_Semesters varchar(5),
FOREIGN KEY (Classes_id, year_Semesters,courses_acronym) REFERENCES Classes(id,year_Semesters, courses_acronym),
PRIMARY KEY(Classes_id,courses_acronym,year_Semesters,Group_id)
);
Normally, you do not (need to) reset the identity column of a table. An identity column is used to create unique values for every single record in a table.
So you want to generate entries in your groups table based on new entries in your classes table. You might create a trigger on your classes table for that purpose.
Since Group_id is already unique by itself (because of its IDENTITY), you do not need other fields in the primary key at all. Instead, you may create a separate UNIQUE constraint for the combination (Classes_id, courses_acronym, year_Semesters) if you need it.
And if the id field of your classes table is an IDENTITY column too, you could define a primary key in your classes table solely on that id field. And then your foreign key constraint in your new groups table can only include that Classes_id field.)
So much for now. I guess that your database design needs some more additional tuning and tweaking. ;)
where are you setting the values from?, you can have a stored proc and in your query have the columns have an initial value set when stored proc is hit assuming there are values at the beginning
.Then use an IF statement.
declare #initial_Classes_id varchar(2) = --initial value inserted
declare #initial_courses_acronym varchar(4) = --initial value inserted
declare #initial_year_Semesters varchar(5) = --initial value inserted
declare #compare_Classes_id varchar(2) = (select top 1 Classes_id from Classes_Groups order by --PK column desc for last insert); l would add Dateadded and then order with last insert date
declare #compare_courses_acronym varchar(2) = (select top 1 Classes_id from Classes_Groups where Classes_id = #compare_Classes_id);
declare #compare_year_Semesters varchar(2) = (select top 1 Classes_id from Classes_Groups where Classes_id = #compare_Classes_id);
IF (#initial_Classes_id != #compare_Classes_id OR #initial_courses_acronym != #compare_courses_acronym OR #initial_year_Semesters != #compare_year_Semesters)
BEGIN
DBCC CHECKIDENT ('Group_id', RESEED, 1)
Insert into Classes_Groups (courses_acronym,year_Semesters)
values (
courses_acronym,
year_Semesters
)
END
ELSE
BEGIN
Insert into Classes_Groups (courses_acronym,year_Semesters)
values (
courses_acronym,
year_Semesters
)
END
NB: would advice to use int on the primary key. Unless you have a specific purpose of doing so.
I am working on an event management project. In that project, I have a form in admin panel as add event which contains events name, category, sub-category, event admin etc and more. And in the database, I have different tables like event category, event sub-category.
And also I have a table that is cultural event which includes form fields and foreign key. I pass event catid, event sub-cat id.
On button click that cultural event is added.
I want to insert data in their tables and I want id that I gave in cultural event table.
On single click I want to insert this
How can I achieve this? Using a stored procedure?
CREATE TABLE EVENT_SCAT (ESUBCAT_ID INT NOT NULL PRIMARY KEY, ECAT_ID INT NOT NULL FOREIGN KEY REFERENCES EVENT_CAT(ECAT_ID), ESUBCAT_NAME VARCHAR(255) NOT NULL, )
create table EVENT_CAT (ECAT_ID INT NOT NULL IDENTITY PRIMARY KEY, ECAT_NAME VARCHAR(255)NOT NULL, EID INT NOT NULL FOREIGN KEY REFERENCES EVENTDETAILS(EID)
CREATE TABLE Cultural_E (c_ID INT NOT NULL IDENTITY PRIMARY KEY, cEVENT_NAME VARCHAR(255) NOT NULL, cE_SDATE DATE NOT NULL, cE_EDATE DATE NOT NULL, SE_RULES1 VARCHAR(MAX), SE_RULES2 VARCHAR(MAX), SE_RULES3 VARCHAR(MAX), cE_RULES4 VARCHAR(MAX), cE_EFEES INT, EID INT NOT NULL FOREIGN KEY REFERENCES EVENTDETAILS(EID), ECAT_ID INT NOT NULL FOREIGN KEY REFERENCES EVENT_CAT(ECAT_ID) )
and i have form in asp.net which includes all fields in single form but there are different tables with foreign keys. and i want id of ecat id and subcatid in last table i.e Cultural_e.
for ex:THESE ARE TABLE
eVENT_T
ID ENAME EADMIN
1 CULTURAL NIKHIL
E_CAT
ID ECAT_NAME E_iD
1 SINGING 1
event_scat
ID eCAT_iD ESUBCAT_NAME
1 1 SOLO
NOW I HAVE TABLE THAT IS CULTURAL_T
THESE TABLE HAVE ITS OWN FILEDS AS WELL AS FOREIGN KEY LIKE EID ,ECAT_ID AS YOU CAN SEE ABOVE
AND I HAVE FORM IN ASP.NET AND FORM CONTAINS TEXTBOX TO ENTER DATA OF ALL THESE TABLE.
SO PLZ TELL ME HOW TO ACHIEVE THIS
THANK YOU
As per my understanding of your question,try to use triggers rather than stored procedures if possible.
CREATE TRIGGER InsertEvents
AFTER INSERT ON EVENT_CAT
BEGIN
/* Insert Query to EVENT_SCAT */
/* Insert Query to cultural */
END
I've created a insert stored procedure with two tables like in the exapmle:
Table NameAge
CREATE TABLE [dbo].[Assignment3_NameAge]
(
userID int PRIMARY KEY IDENTITY(1,1),
Name varchar(255) NOT NULL,
Age int NOT NULL
)
Table Hobbies
CREATE TABLE [dbo].[Assignment3_Hobbies]
(
hobbiesID int Identity(1,1) Primary Key,
userID int Foreign Key references Assignment3_NameAge(userID),
hobbies varchar(255) NOT NULL,
)
Insert Stored Procedure
CREATE PROCEDURE [dbo].p_Assignment3Join_ins
#Name nvarchar(100),
#Age int,
#Hobbies nvarchar(100)
AS
INSERT INTO [TABLE].[dbo].[Assignment3_NameAge]
([Name]
,[Age])
VALUES (#Name,#Age)
INSERT INTO [TABLE].[dbo].[Assignment3_Hobbies]
([Hobbies])
VALUES (#Hobbies)
The problem is that when i run the stored procedure the table Hobbies has a null value for userid(the foreign key)
What am i doing wrong?
You should provide the key of the Assignment3_NameAge value you want to insert into Assignment3_Hobbies.
If you want the last inserted you can use SCOPE_IDENTITY() from SQL Server(if you're using SQL Server) or equivalent. It will give you the last inserted value from Assignment3_NameAge
I am guessing this is SQL Server based on the IDENTITY column. Correct?
The first insert creates a user, but there is no user ID being set on the insert of the hobby. You need to capture the identity value from the first insert to be used in the second insert. Have you gon over the system functions available?
You're not supplying a value for it, SQL won't automagically fill the value in for you even though you've created a Foreign Key relationship. It's your job to populate the tables.
I'm using SQL Server 2005 and wish to create a number address records, updating the contact records with the new Id's:
Take the following tables
create table contact(id int primary key identity, home_address_id int, work_address_id int)
create table address(id int primary key identity, street varchar(25), number int)
And foreign keys:
ALTER TABLE dbo.contact ADD CONSTRAINT FK_contact_address1 FOREIGN KEY (home_address_id) REFERENCES dbo.address(id)
ALTER TABLE dbo.contact ADD CONSTRAINT FK_contact_address2 FOREIGN KEY (work_address_id) REFERENCES dbo.address(id)
some dummy data
insert into contact default values
insert into contact default values
insert into contact default values
How can I insert a default empty address record for all contacts who have no home address, and update the home_address_id in one go?
The first part is simple:
insert into address(street) select null from contact where home_address_id is null
I can even get the newly create address id's:
declare #addressTable table(id int)
insert into address(street)
OUTPUT INSERTED.Id INTO #addressTable
select null from contact where home_address_id is null
Here's the new id's
select * from #addressTable
But how to update the contact table with these new Id's?
If possible, I would suggest normalizing your database by adding a Contact_Addresses table:
CREATE TABLE Contact_Addresses
(
contact_id INT NOT NULL,
address_id INT NOT NULL,
address_type VARCHAR(10) NOT NULL,
CONSTRAINT PK_Contact_Addresses PRIMARY KEY CLUSTERED (contact_id, address_id, address_type),
CONSTRAINT FK_ContactAddresses_Contacts (contact_id) REFERENCES Contacts (id),
CONSTRAINT FK_ContactAddresses_Addresses (address_id) REFERENCES Addresses (id),
CONSTRAINT CK_ContactAddresses_address_type CHECK address_type IN ('HOME', 'WORK')
)
Next, I would suggest not putting "dummy" records in your database. It's going to end up causing headaches down the road. The database should contain an accurate record of the data in your system. If you want to display some value by default when no address exists in the system for a contact then handle that in your UI.
If you really must though, then the following code should do the trick:
;WITH C_CTE AS
(
SELECT
id,
home_address_id,
ROW_NUMBER() OVER(ORDER BY id) AS seq
FROM
Contacts
),
(
SELECT
id,
ROW_NUMBER() OVER(ORDER BY id) AS seq
FROM
Addresses
)
UPDATE
C_CTE
SET
home_address_id = A.id
FROM
C_CTE C
INNER JOIN A_CTE A ON A.seq = C.seq
I would do it from the moment you get a new contact, thusly:
[receive contact information]
//prior to inserting contact
declare #homeAddress int, #workAddress int
[insert home address here (real or default based on input)]
set #homeAddress = ##Identity
[insert work address here (real or default)]
set #workAddress = ##Identity
[insert contact here referencing #homeAddress & #workAddress]
For the stuff already in your table, you're going to have to associate all of your null value ids to a contact id. Or, you could clear out your null value addresses, and modify the above statement to an update somehow (brain's not working at the moment, so all I'm coming up with is a cursor, and cursors are evil).
I need help in auto populating the primary key values in foreign key table while inserting data in foreign key table. For Example: I have created table:
create table Patient
(
PatientId int IDENTITY(1,1) primary key,
FirstName varchar(50),
SurName varchar(50),
Gender char(20),
)
Say 5 rows are there in this Patient Table:
Say First Row value is: 1, Priya, Kumari, Female
I have created the Guardians Table:
create table Guardians
(
GuardiansId int identity(1,1) primary key,
PatientId int foreign key references Patient(PatientId),
FirstName varchar(50),
SurName varchar(50),
Gender char(20),
RelationToPatient varchar(50),
)
In this table Insert operations are like this:
insert into Guardians(FirstName, SurName, Gender,RelationToPatient)values('Sumit','Kumar','Male','Wife')
While selecting the Guardians Table PatientId showing NULL values: My query is while inserting the values in Guardians Table PatientId should be auto Populated which will come from Patient Table...
My second problem is: How to create the Identity column as varchar. For example: suppose I want to increment my Guardians Table with 'GRD0001', 'GRD0002', 'GRD0003' like this...
Thanks,
S.D
Your question is not very clear - what exactly do you want to do??
When you insert something into the Guardians table, you want to automatically also insert it into the Patients table? I don't quite follow. Can you make a complete example, maybe??
If you need to capture the insert IDENTITY value from the Patient table, do this:
DECLARE #NewPatientID INT
INSERT INTO dbo.Patient(fields) VALUES(.......)
SET #NewPatientID = SCOPE_IDENTITY()
INSERT INTO dbo.Guardians(PatientId, ......) VALUES(#NewPatientID, ......)
As for your second question: leave you GuardiansId IDENTITY as it is (only an INT column can be an IDENTITY and you want to keep that - trust me!) and add a computed column to your table:
ALTER TABLE dbo.Guardians
ADD GuardianIDWithPrefix AS
'GDR' + RIGHT('0000' + CAST(GuardiansId AS VARCHAR(4)), 4) PERSISTED
Since it's a PERSISTED field, you can even index on it and use it like a normal field in every respect.
That should do the trick!