I have created a movie database that contain following tables :
1.Film
2.People
3.Genres
4.Role
5.Users
Here is my sql
create table Film ( id INT(30),title varchar(30),images varchar(30)
primary key (id));
create table people(id INT(30),Fname varchar(30),Lname varchar(30),
primary key (id));
create table Role(id INT(30), name varchar(30),
primary key(id));
i want create relation between Film,People and Role table.SO my Question is do i need to create a table to make relation between those table and is it necessary to use auto_increment for id column?
You'd want to create some tables like:
FilmRole( FilmId INT, RoleId INT) these 2 columns would make your PK and they are also FK's to their
FilmPeople (FilmId INT, PeopleId INT) respective source tables.
FilmUsers( FilmId INT, UserId INT)
You could add a single IDENTITY (for SQL Server for example) column to each table if you wanted but in this particular case a 2 column PK is adequate as these tables simply point to other records.
You need to alter your table and add in a foreign key (Primary key in one table and attribute in another). Examples how to do it here! http://www.w3schools.com/sql/sql_foreignkey.asp
do i need to create a table to make relation between those table ?
YES ! to enforce Referential integrity read this
is it necessary to use auto_increment for id column?
Depends but it is most prefered way of creating a PK on a table
Related
I need to create a table explaining how one representative reports to another but dont know quite how?
Create table Representative (RID int , TOID int, Rname varchar(10), Rphone varchar(15), PRIMARY KEY (RID), FOREIGN KEY (TOID) REFERENCES TourOperator);
The code above is my attempt but dont know how to introduce the reports to
do I create another variable called super_ID? and add it to table or how can i relate one representative to another in the table
Yes, you'd add another column (SUPER_ID) into the table which will be a foreign key, pointing to RID.
I am piggy backing off this question regarding creating a junction/linking table. It is clear how to create a junction table, but I am concerned about how to fill the junction table with data. What is the simplest and/or best method for filling out the junction table (movie_writer_junction) with data between two other tables (movie, writer)
CREATE TABLE movie
(
movie_id INT NOT NULL IDENTITY(1, 1) PRIMARY KEY,
movie_name NVARCHAR(100),
title_date DATE
);
CREATE TABLE writer
(
writer_id INT NOT NULL IDENTITY(1, 1) PRIMARY KEY,
writer_name NVARCHAR(100),
birth_date DATE
);
INSERT INTO movie
VALUES ('Batman', '2015-12-12'), ('Robin', '2016-12-12'),
('Charzard, the movie', '2018-12-12')
INSERT INTO writer
VALUES ('Christopher', '1978-12-12'), ('Craig', '1989-12-12'),
('Ash', '1934-12-12')
CREATE TABLE movie_writer_junction
(
movie_id INT,
writer_id INT,
CONSTRAINT movie_writer_pk
PRIMARY KEY(movie_id, writer_id),
CONSTRAINT movie_id_fk
FOREIGN KEY(movie_id) REFERENCES movie(movie_id),
CONSTRAINT writer_fk
FOREIGN KEY(writer_id) REFERENCES writer(writer_id)
);
The final junction table is currently empty. This is a simple example, and you can manually fill the data into the junction table, but if I have two tables with millions of rows, how is something like this completed?
Hi I'm guessing this relates to the fact that you can't rely on the Identity Columns being the same in different regions.
You can write your inserts as a cross join from the 2 src tables
Insert junc_table (writer_id, movie_id)
Select writer_id , movie_id
from writer
CROSS Join
movie
where writer_name = 'Tolkien' and movie_name = 'Lord of the Ring'
This way you always get the correct Surrogate Key (the identity) from both tables.
Its pretty easy to generate a SQL statement for all your existing junction combinations using a bit of Dynamic SQL
Another Approach is to Use SET IDENTITY_INSERT ON - but this needs to be done when loading the 2 other tables and that ship may already have sailed!
I'm creating er-diagram for "Airport" database. And I got stick with tables "Flight" and "Airport" .
In table "Flight" I have 2 columns: "Departure_place" and "Arrival_ place". Both of it should be connected to values in table "Airport".
So, How can I make that in the proper way on er-diagram and on sql?
I think you are looking for foreign keys. Here is a tutorial for that:
https://www.w3schools.com/sql/sql_foreignkey.asp
In your case first create the tables:
create table flight(
idFlight int primary key,
idDeparturePlace int,
idArrivalPlace int);
create table airport(
idAirport int primary key);
Now you have to add tow foreign keys. One for idDepaturePlace and one for idArrivalPlace.
Follow this syntax:
ALTER TABLE <child table> ADD FOREIGN KEY (<col in child table>) REFERENCES <master table>(<col in master table>);
In your case you have to add this both keys to your flight table:
ALTER TABLE flight ADD FOREIGN KEY (idDepaturePlace) REFERENCES airport(idAirport);
ALTER TABLE flight ADD FOREIGN KEY (idArrivalPlace) REFERENCES airport(idAirport);
Is there a way to store multiple values in a column that has a foreign key constraint?
Let's say I have a states table and a project table. Project table has a foreign key constraint with states table. Now we are implementing the same project in three different states. How can I select multiple states?
Sample
Create table states (
Stateid int identity primary key,
State varchar(100)
);
Projects Table
Create table projects (
ProjId int primary key identity,
ProjTitle varchar (100),
Budget decimal,
);
How can I insert multiple values in projects states table?
Based on TPHE answer lets me create another table called projectstates
Create table projectstates(
projStatid int identity primary key,
stateid int,
ProjId int
constraint fk_ProjId foreign key (ProjId) references Projects(ProjId),
constraint fk_stateid foreign key (stateid) references states(StateId)
);
Now how can i insert data in ProjectStates while adding project to the project table?
The best way I've found to do this is to create the second table with no foreign key constraint at first. Then you can populate both tables with the data, then introduce the constraint afterwards - assuming the data in the tables complies with the constraint.
Also, if a many to many relationship exists, add in a mapping table to allow this.
It would break some basic rules of database design to add multiple values. You should create a new table that has a one to many relationship with the states table (each state can have multiple values in the new table) and contains a column for the associated project IDs (also with a one-to-many relationship). Then you would join from the states table to the new table and then to the projects table or vice versa. More info on how and why to design databases in this way.
I would like to apologize first about my title, because I understand it may be technically incorrect
I currently have a database with multiple tables, 4 of them are relevant in this example.
FORMS
FIELDS
ENTRIES
VALUES
Below is a shortened version of the tables
Create table Form_Master
(
form_id int identity primary key ,
form_name varchar(255) ,
form_description varchar(255),
form_create_date date ,
)
Create table Field_Master
(field_id int identity primary key,
form_ID int foreign key references Form_Master(form_id),
field_name varchar(255),
type_ID int
)
Create table Entry_Master
(
entry_id int identity primary key,
entry_date date,
form_id int foreign key references Form_Master(form_id),
)
Create table Value_Master
(
value_id int identity primary key,
value varchar(255),
field_id int foreign key references Field_Master(field_id),
entry_id int foreign key references Entry_Master(entry_id),
)
The purpose of these tables is to create a dynamic method of capturing and retrieving information - a form is a table, a field is a column, and entry is a row and a value is a cell
Currently when I am retrieving information from a form, I create a temporary table, with columns as such in the field_master, then select all entries linked to the form, and the values linked to those entries, and insert them into the temporary table I have just created.
The reason for the temporary table is to restructure the data into an organised format and display it in a DataGridView.
My problem is one of performance, creating the table as mentioned above is becoming slower as forms exceed fields > 20 or entries linked to a form exceeds > 100
My questions are:
Is there a way to select the data directly from field_master in the format of the temporary table mentioned above?
Do you think I should re-think my database design?
Is there an easier method to do what I am trying to do?
Any input will be appreciated, I do know how to use Google, however in this instance I am not sure what exactly to look for, so even a keyword would be nice.