I have two tables:
Table 1 - projects and the structure is
create table Projects
(
ProjectID int identity(1,1) primary key ,
ProjectName varchar(900) not null,
ProjectCity varchar(500) not null,
ProjectAddress varchar(900) not null,
ProjectStatus bit not null,
projectCategories int not null ,
constraint fk2
foreign key(projectCategories)
references Categories(CategoriesID )
)
Table 2 is
create table imgProject
(
ProjectID int identity(1,1) primary key ,
Imagecontent image not null,
FkProject int not null ,
constraint fk1
foreign key(FkProject)
references Projects(ProjectID)
on delete cascade
)
How can I return project with only one row from table img project
I mean I want return all the project with only one column from table imgProject.
and example
After execute the query
id project [1] , NameProject [test] , Imagecontent [data]
not return all the row match with id foreign key on table imgproject
Related
How primary key in one table connect to another table with the same primary key?
I am trying to make it like this, which those two primary key in the table of CustomerCreditCard is connect to the table of Customer and table of Credit card]
https://i.stack.imgur.com/lIBUE.png
--3
CREATE TABLE Customer
(
CustomerID INT IDENTITY PRIMARY KEY,
FirstName VARCHAR(50) NOT NULL,
LastName VARCHAR(50) NOT NULL,
);
--5
CREATE TABLE CreditCard
(
CreditCardNumber VARCHAR(16) PRIMARY KEY,
CreditCardOwnerName VARCHAR(50) NOT NULL,
);
--6
CREATE TABLE CustomerCreditCard
(
CreditCardNumber VARCHAR(16) NOT NULL,
CustomerID INT IDENTITY NOT NULL,
PRIMARY KEY(CreditCardNumber, CustomerID)
);
--6
CREATE TABLE CustomerCreditCard
(
CreditCardNumber VARCHAR(16) NOT NULL,
CustomerID INT NOT NULL,
CONSTRAINT pk_CustomerCreditCard
PRIMARY KEY(CreditCardNumber,CustomerID ),
CONSTRAINT fk_CustomerCreditCard_CreditCardNumber
FOREIGN KEY(CreditCardNumber)
REFERENCES CreditCard(CreditCardNumber)
ON DELETE CASCADE ON UPDATE CASCADE,
CONSTRAINT fk_CustomerCreditCard_CustomerID
FOREIGN KEY(CustomerID)
REFERENCES Customer(CustomerID)
ON DELETE CASCADE ON UPDATE CASCADE
);
To solve the problem of this question, add the foreign key to the table that has two primary keys, then reference to other tables that you want to connect with the same primary key.
When creating the foreign key I came across this error. Below is my code.
create table tblPerson(
ID int not null primary key,
Fullname varchar(50) not null,
Email varchar(50) not null,
GenderId int
)
create table tblGender (
ID int not null primary key,
Gender varchar(50) not null
)
alter table tblPerson add constraint tblPerson_GenderId_FK
foreign key (GenderId) references tblGender(ID)
You want to identify any "do not align" rows....
I have made the below.
You won't be able to add the FK constraint, if any rows come back from the SELECT query.
I have also removed the hungarian notation for "tbl". I would advise against it.
create table dbo.Person(
ID int not null primary key,
Fullname varchar(50) not null,
Email varchar(50) not null,
GenderId int )
create table dbo.Gender (
ID int not null primary key,
Gender varchar(50) not null
)
/* any rows below? your FK creation will fail */
Select *, p.GenderId as 'HoustonWeHaveAProblemValue' from dbo.Person p Where Not Exists (Select 1 from dbo.Gender g where g.ID = p.GenderId)
alter table dbo.Person add constraint Person_GenderId_FK
foreign key (GenderId) references dbo.Gender(ID)
Hi please use the following code to achieve your goal :
1-First create tblGender:
create table tblGender (
ID int not null primary key,
Gender varchar(50) not null
)
2-Then create table tblPerson with the relationship between 2 tables since the beginning:
create table tblPerson(
ID int not null primary key,
Fullname varchar(50) not null,
Email varchar(50) not null,
GenderId int references tblGender(ID)
)
works fine.
Here is my code it generates Foreign key conflict error
CREATE TABLE tblProducts
(
ProductID int NOT NULL IDENTITY PRIMARY KEY,
ProductName nvarchar(30) NOT NULL,
BatchID int NOT NULL FOREIGN KEY REFERENCES tblBatches (BatchID)
)
CREATE TABLE tblBatches
(
BatchID INT NOT NULL IDENTITY PRIMARY KEY,
BatchCode nvarchar(20) NOT NULL,
Quantity int NOT NULL,
BatchMnf Date NOT NULL,
BatchExp Date NOT NULL,
PurchaseRate int NOT NULL,
SalesRate int NOT NULL,
ProductID int NOT NULL FOREIGN KEY REFERENCES tblProducts (ProductID)
)
You cannot do that. This is a circular reference.
This is a bad design but if you want to do that, you need to make foreign key columns Nullable.
CREATE TABLE tblProducts
(
ProductID int NOT NULL IDENTITY PRIMARY KEY,
ProductName nvarchar(30) NOT NULL,
BatchID int NULL FOREIGN KEY REFERENCES tblBatches (BatchID)
)
CREATE TABLE tblBatches
(
BatchID INT NOT NULL IDENTITY PRIMARY KEY,
BatchCode nvarchar(20) NOT NULL,
Quantity int NOT NULL,
BatchMnf Date NOT NULL,
BatchExp Date NOT NULL,
PurchaseRate int NOT NULL,
SalesRate int NOT NULL,
ProductID int NULL FOREIGN KEY REFERENCES tblProducts (ProductID)
)
Then you need to update reference fields after inserting records in tblBatches and tblProducts.
The good design says you need to create a bridge table like this:
CREATE TABLE tblProductsBatch
(
ID int NOT NULL IDENTITY PRIMARY KEY,
ProductID int NOT NULL,
BatchID int NOT NULL
)
And after inserting product and batch, you need to insert a record in this table to link rows to each other.
CREATE TABLE Schedule
(
Section DATETIME NOT NULL PRIMARY KEY(CourseID, Section, EmployeeID),
CourseID VARCHAR(10) REFERENCES Course(CourseID) NOT NULL,
EmployeeID VARCHAR(20) NOT NULL REFERENCES Employee(EmployeeID),
StartTime TIME NULL,
Days DATE NULL,
Length TIME NULL
)
CREATE TABLE Enrollment
(
StudentID INT Primary key (StudentID, CourseID, Section) NOT NULL,
CourseID VARCHAR(10) REFERENCES Course(CourseID) NOT NULL,
Section DATETIME NOT NULL REFERENCES Schedule(Section)
)
2nd table did not get created, where did I go wrong?
Its because you made the primary key in the Schedule table a natural/combined key.
Try creating a stand alone column for this purpose instead. I've included an example below that shows the differences.
CREATE TABLE DBO.PK_TEST (
Col_A INT NOT NULL
,Col_B INT NOT NULL
,Primary Key(Col_A,Col_B)
)
Create table DBO.PK_TEST_2 (
Col_A int NOT NULL
,Col_B int NOT NULL
,Col_C as (cast(Col_A as nvarchar)
+ cast(Col_B as nvarchar)) PERSISTED NOT NULL
,primary key(Col_C)
)
I have the following T-SQL schema. The problem I am having is that the check constraint on the Download table is not working. I am still able to insert records into that table that contain NULL values for both ProductId and CategoryId. Why is this so?
I want both the ProductId and CategoryId columns to allow NULL values, but for any given record only one of these are allowed to be set to NULL, the other needs to be a corresponding Id of the Category or Product table.
CREATE TABLE Category (
Id int IDENTITY(1,1) NOT NULL PRIMARY KEY,
Description nvarchar(100) NULL,
ParentCategoryId int NULL
CONSTRAINT fk_CategoryId_CategoryId FOREIGN KEY (Id) REFERENCES Category(Id)
)
GO
CREATE TABLE Product (
Id int IDENTITY(1,1) NOT NULL PRIMARY KEY,
Title nvarchar(100) NOT NULL,
TagLine nvarchar(MAX) NOT NULL,
Description nvarchar(MAX)NULL,
CategoryId int NOT NULL,
ImageUrl nvarchar(255) NULL,
Keywords nvarchar(200) NOT NULL
CONSTRAINT fk_ProductCategoryId_CategoryId FOREIGN KEY (CategoryId) REFERENCES Category(Id)
)
GO
CREATE TABLE Download (
Id int IDENTITY(1,1) NOT NULL PRIMARY KEY,
Title nvarchar(100) NOT NULL,
Description nvarchar(MAX) NULL,
CategoryId int NULL,
ProductId int NULL,
DownloadUrl nvarchar(255) NOT NULL,
CONSTRAINT fk_DownloadCategoryId FOREIGN KEY (CategoryId) REFERENCES Category(Id),
CONSTRAINT fk_DownloadProductId FOREIGN KEY (ProductId) REFERENCES Product(Id),
CONSTRAINT chk_ReferencesCategoryOrProduct CHECK (ProductID != NULL AND CategoryId != NULL)
)
GO
Use:
CONSTRAINT chk_ReferencesCategoryOrProduct CHECK (ProductID IS NOT NULL
OR CategoryId IS NOT NULL)
NULL isn't a value -- it's a placeholder for the lack of a value. Which is why you need to use specific syntax to check for it.