I have 2 tables:
create table numbers2
(
id1 int IDENTITY(1,1) not null,
id2 int not null,
primary key(id1, id2)
)
and table 2
create table ttt
(
id int identity(1,1) not null,
first_name varchar(50) null,
last_name varchar(50) null,
sex varchar(1) check (sex in ('m', 'f')) null,
number_id int not null,
id_id1 int not null,
id_id2 int not null,
primary key(id),
constraint fk_numbers_id1 foreign key (id_id1) references numbers2(id1)
on update no action
on delete no action
)
The problem is how to add constraint "fk_numbers_id1" so it will only reference one part of the composite key from table numbers2. Is it possible or there is other solution?
Create a unique constraint on numbers2.id1:
create table numbers2
(
id1 int IDENTITY(1,1) not null,
id2 int not null,
primary key(id1, id2),
unique(id1)
)
I would like to know why you chose to create the primary key over two columns, where the first column is already unique by itself. I'm sure this violates some kind of Normal Form rule but I can't remember which one.
If you did it in order to cover the data in both columns, then it is unnecessary to do that, just do this instead (assuming that the data in id1 is genuinely unique):
create table numbers2
(
id1 int IDENTITY(1,1) not null,
id2 int not null,
primary key(id1),
)
create index cover_id2 on numbers2(id2) -- no need to include clustered index columns in a covering index
Related
CREATE TABLE student
(
student_id INT PRIMARY KEY,
first_name VARCHAR(40) NOT NULL,
last_name VARCHAR(40) NOT NULL,
birth_day DATE NOT NULL,
sex VARCHAR(1) NOT NULL,
student_email_address VARCHAR(40) NOT NULL UNIQUE,
student_password VARCHAR(10) NOT NULL UNIQUE,
student_nick_name VARCHAR(10) NOT NULL,
student_qualification VARCHAR(10) NOT NULL,
student_documents VARCHAR(255) NOT NULL,
student_image VARCHAR(100) NOT NULL
);
CREATE TABLE student_feedback
(
sr_no BIGSERIAL PRIMARY KEY,
student_id INT NOT NULL,
feedback_type VARCHAR(10) NOT NULL,
feedback_text VARCHAR(200) NOT NULL,
FOREIGN KEY (student_id) REFERENCES student(student_id)
);
CREATE TABLE online_exam
(
exam_id INT PRIMARY KEY,
exam_title VARCHAR(20) UNIQUE NOT NULL,
exam_duration_min INT NOT NULL,
total_questions INT NOT NULL,
marks_per_right_answer INT NOT NULL,
marks_per_wrong_answer INT NOT NULL,
passing_marks INT NOT NULL,
exam_status VARCHAR(2)
);
CREATE TABLE exam_subjects
(
sub_id INT,
exam_id INT,
sub_name VARCHAR(20) NOT NULL,
sub_desc VARCHAR(20) NOT NULL,
UNIQUE(sub_id,exam_id),
PRIMARY KEY(sub_id,exam_id),
FOREIGN KEY (exam_id) REFERENCES online_exam(exam_id) ON DELETE CASCADE
);
CREATE TABLE sub_questions
(
sub_id1 INT,
ques_id INT,
ques_text VARCHAR(150) NOT NULL,
ques_attachments VARCHAR(255),
option_1 VARCHAR(20) NOT NULL,
option_2 VARCHAR(20) NOT NULL,
option_3 VARCHAR(20) NOT NULL,
option_4 VARCHAR(20) NOT NULL,
UNIQUE(sub_id1,ques_id),
PRIMARY KEY (sub_id1,ques_id),
FOREIGN KEY (sub_id1) REFERENCES exam_subjects(sub_id) ON DELETE CASCADE
);
CREATE TABLE ques_answers
(
ans_id INT,
ques_id INT,
ans VARCHAR(20) NOT NULL,
PRIMARY KEY (ans_id,ques_id),
FOREIGN KEY (ques_id) REFERENCES sub_questions(ques_id) ON DELETE CASCADE
);
CREATE TABLE exam_registration
(
student_id INT,
exam_id INT,
exam_date_time TIMESTAMP NOT NULL,
PRIMARY KEY (student_id,exam_id),
FOREIGN KEY (student_id) REFERENCES student(student_id) ON DELETE CASCADE,
FOREIGN KEY (exam_id) REFERENCES online_exam(exam_id) ON DELETE CASCADE
);
CREATE TABLE exam_result
(
student_id INT,
exam_id INT,
sub_id INT,
marks_scored INT NOT NULL,
correct_ques INT NOT NULL,
wrong_ques INT NOT NULL,
grade VARCHAR(10) NOT NULL,
PRIMARY KEY(student_id,exam_id,sub_id),
FOREIGN KEY (student_id) REFERENCES student(student_id) ON DELETE CASCADE,
FOREIGN KEY (exam_id) REFERENCES online_exam(exam_id) ON DELETE CASCADE,
FOREIGN KEY (sub_id) REFERENCES exam_subjects(sub_id) ON DELETE CASCADE
);
Output :
CREATE TABLE,
CREATE TABLE,
CREATE TABLE,
CREATE TABLE,
There is no unique constraint matching given keys for referenced table "exam_subjects", relation "sub_questions" do not exist,
CREATE TABLE,
There is no unique constraint matching given keys for referenced table "exam_subjects".
Why am I getting "there is no unique..." error in postgresql? How to solve it? Please help.
In your table exam_subjects the primary key is a compossed key (PRIMARY KEY(sub_id, exam_id))
Therefore, your table sub_questions must have both columns to create the constraint, otherwise you get the error about unique constraints (or you can create a unique field acting as primary key, and create a unique index on both columns sub_id and exam_id)
This is code to create the beginnings of a book library database with Microsoft SQL Server Management Studio.
CREATE DATABASE BOOK_LIBRARY
CREATE TABLE LIBRARY_USER
(
usr_id int not null primary key,
f_name varchar(30) not null,
m_init char(1),
l_name varchar(30) not null,
balance decimal(6,2),
join_date date,
addrss_1 varchar(30) not null,
addrss_2 varchar(30),
city varchar(30) not null,
addrss_state char(2) not null,
zip_code varchar(10) not null,
email varchar(30)
);
CREATE TABLE LIBRARY_TRANSACTIONS
(
transaction_id int not null primary key,
maximum_borrow_duration int not null,
strt_date date not null,
actual_return_date date not null,
borrow_usr_id int not null,
foreign key (borrow_usr_id) references LIBRARY_USER(usr_id)
);
CREATE TABLE BOOKS
(
isbn varchar(17) not null primary key,
title varchar(30) not null,
number_of_copies int not null,
Author varchar(30) not null,
Number_of_pages int not null,
publish_year int not null,
book_type varchar(20)
);
CREATE TABLE DIGITAL_BOOKS
(
digital_id int not null primary key,
format varchar(30) not null,
size_mb int not null,
digital_isbn varchar(17) not null,
foreign key(digital_isbn) references BOOKS(isbn)
);
CREATE TABLE PHYSICAL_BOOKS
(
physical_id int not null primary key,
condition varchar(20) not null,
physical_isbn varchar(17) not null,
foreign key(physical_isbn) references BOOKS(isbn)
);
CREATE TABLE BOOK_COPY
(
digi_id int not null,
phys_id int not null,
primary key(digi_id, phys_id),
foreign key(digi_id) references DIGITAL_BOOKS(digital_id),
foreign key(phys_id) references PHYSICAL_BOOKS(physical_id)
);
CREATE TABLE CONTNS
(
trans_id int not null primary key,
digi_id int not null,
phys_id int not null,
foreign key(digi_id) references BOOK_COPY(digi_id),
foreign key(phys_id) references BOOK_COPY(phys_id)
);
Despite me being able to look and see that digi_id and phys_id are in fact primary keys of the book_copy table, I keep getting this error:
Msg 1776, Level 16, State 0, Line 66
There are no primary or candidate keys in the referenced table 'BOOK_COPY' that match the referencing column list in the foreign key 'FK__CONTNS__digi_id__37A5467C'.
Msg 1750, Level 16, State 1, Line 66
Could not create constraint or index. See previous errors.
Am I missing something obvious? I'm just starting out with using this program, so any help is greatly appreciated.
Here:
CREATE TABLE CONTNS
(
trans_id int not null primary key,
digi_id int not null,
phys_id int not null,
foreign key(digi_id) references BOOK_COPY(digi_id),
foreign key(phys_id) references BOOK_COPY(phys_id)
);
You are creating two foreign keys to parent table BOOK_COPY. But that table has a compound primary key (ie a multi-column primary key)
CREATE TABLE BOOK_COPY
(
digi_id int not null,
phys_id int not null,
primary key(digi_id, phys_id), --> here
...
)
As a consequence, you need a compound foreign key:
CREATE TABLE CONTNS
(
trans_id int not null primary key,
digi_id int not null,
phys_id int not null,
foreign key(digi_id, phys_id) references BOOK_COPY(digi_id, phys_id)
);
create database shop1
use shop1
create table mathang
(
MatHangID INT primary key not null,
TenMatHang varchar(50),
SoLuong int not null,
Price int not null,
)
create table nhacungcap
(
MatHangID INT foreign key references mathang,
TenNhaCungCap varchar(50) ,
DiaChi varchar(100),
SoDienThoai int ,
CONSTRAINT pk_M_CC primary key (MatHangID)
)
create table khachhang
(
KhachHangID int not null primary key,
TenKhachHang varchar(50) not null,
[DiaChi] varchar(100) not null,
[SoDienThoai] varchar(50) not null,
)
create table donhang
(
DonHangID int references to khachhang(KhachHangID),
TenDonHang varchar(50),
SoLuong int,
CONSTRAINT pk_DHID primary key (DonHangID)
)
I can not find errors with this, it shows the foreign key error to add this relation ship. Any one please help.
Remove the to in
...
DonHangID int references to khachhang(KhachHangID)
...
to get
...
DonHangID int references khachhang(KhachHangID)
...
. The to doesn't belong there syntactically.
I'm trying to run this query but SQL -erver stopped me with this error:
Foreign key 'FK__food__groupid__3F115E1A' references invalid column 'groupid' in referenced table 'sub'.
This is my query:
create table menu
(
valedid int primary key not null,
name nvarchar(50) not null,
)
create table sub
(
qroupid int primary key not null,
groupname nvarchar(50) not null,
valedid int not null,
foreign key(valedid) references menu (valedid),
)
create table food
(
foodid int primary key not null,
radif int identity(1,1) not null,
qeymat int not null,
name nvarchar(100) not null,
groupid int not null,
foreign key(groupid) references sub(groupid),
)
You create the column with name qroupid and not groupid in table sub
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.