CREATE TABLE location (
uid int not null auto_increment primary key,
name varchar(255) NOT NULL,
`state_uid` int not null,
FOREIGN KEY location(state_uid)
REFERENCES state(uid)
ON UPDATE CASCADE
ON DELETE RESTRICT,
`city_uid` int not null,
FOREIGN KEY location(city_uid)
REFERENCES city(uid)
ON UPDATE CASCADE
ON DELETE RESTRICT,
`area_uid` int not null,
FOREIGN KEY location(area_uid)
REFERENCES area(uid)
ON UPDATE CASCADE
ON DELETE RESTRICT
);
CREATE TABLE location (
uid int not null auto_increment primary key,
name varchar(255) NOT NULL,
state_uid int not null,
city_uid int not null,
area_uid int not null,
CONSTRAINT fk_state FOREIGN KEY (state_uid) REFERENCES state(uid) ,
CONSTRAINT fk_city FOREIGN KEY (city_uid) REFERENCES city(uid) ,
CONSTRAINT fk_area FOREIGN KEY (area_uid) REFERENCES area(uid)
);
Try this query
make sure parent tables exists
Your version is almost just fine. The problem is the location in the foreign key reference.
You have no issue with the cascading stuff or the ordering of the columns. So, this works:
CREATE TABLE location (
uid int not null auto_increment primary key,
name varchar(255) NOT NULL,
`state_uid` int not null,
FOREIGN KEY (state_uid) REFERENCES state(uid) ON UPDATE CASCADE ON DELETE RESTRICT,
`city_uid` int not null,
FOREIGN KEY (city_uid) REFERENCES city(uid) ON UPDATE CASCADE ON DELETE RESTRICT,
`area_uid` int not null,
FOREIGN KEY (area_uid) REFERENCES area(uid) ON UPDATE CASCADE ON DELETE RESTRICT
);
Here is a SQL Fiddle.
Note that it is often traditional to put explicit foreign key (and other constraints) after the column definitions, there is no rule or standard for this. In fact, most databases support in-line foreign key definitions. MySQL does not, however.
Related
CREATE TABLE Infrastructure.OBSModules(
OBSId int FOREIGN KEY REFERENCES Infrastructure.OBS(Id) NOT NULL,
ModuleId int FOREIGN KEY REFERENCES Infrastructure.Module(Id) NOT NULL,
Constraint PK_Infrastructure_OBS_Module Primary Key(OBSId,ModuleId)
)
Go
The above code is my code by which I created Infrastructure.OBSType table,but I deleted foreign keys manually so I cant Insert any rows in my table.how can I recover those foreign keys?
Here are my tables. I need to check that the 'program' attribute referenced in StudentsBranch with the table Students and the table Branches is the same. How can I do it?
CREATE TABLE Programmes (
name VARCHAR(200) UNIQUE NOT NULL,
CONSTRAINT pk_Programmes PRIMARY KEY (name)
);
CREATE TABLE Students (
id NUMERIC(10,0) UNIQUE NOT NULL,
program VARCHAR(200) NOT NULL,
CONSTRAINT pk_Students PRIMARY KEY (idnr),
FOREIGN KEY (program) REFERENCES Programmes(name)
);
CREATE TABLE Branches (
name VARCHAR(200) UNIQUE NOT NULL,
program VARCHAR(200) NOT NULL,
CONSTRAINT pk_Branches PRIMARY KEY (name, program),
FOREIGN KEY (program) REFERENCES Programmes(name)
);
CREATE TABLE StudentsBranch (
student NUMERIC(10,0) NOT NULL,
program VARCHAR(200) NOT NULL,
branch VARCHAR(200) NOT NULL,
CONSTRAINT pk_StudentsBranch PRIMARY KEY (student),
/* Below how the foreign keys I think should be */
FOREIGN KEY (student, program) REFERENCES Students(idnr, program),
FOREIGN KEY (branch, program) REFERENCES Branches(name, program)
/* I need to add a constraint to verify that the 'program' in Students
* and the 'program' in Branches are equivalent. How?
*/
);
You can't write that constraint with that existing database model you have now.
The only way I see you could do it, is by changing the primary key of Students to (id, program):
CREATE TABLE Students (
id NUMERIC(10,0) UNIQUE NOT NULL,
program VARCHAR(200) NOT NULL,
CONSTRAINT pk_Students PRIMARY KEY (id, program),
FOREIGN KEY (program) REFERENCES Programmes(name)
);
Then the table StudentsBranch could naturally enforce both FKs with using the single column program, as in:
CREATE TABLE StudentsBranch (
student NUMERIC(10,0) NOT NULL,
program VARCHAR(200) NOT NULL,
branch VARCHAR(200) NOT NULL,
CONSTRAINT pk_StudentsBranch PRIMARY KEY (student),
FOREIGN KEY (student, program) REFERENCES Students (id, program),
FOREIGN KEY (branch, program) REFERENCES Branches (name, program)
);
It is always a good idea to have an numeric column of primary key and have primary key for every table.
Once you have primary key for every table you can referece primary key of a specific table and refere it as foerign key.
CREATE TABLE Programmes (
ID INT,
name VARCHAR(200) UNIQUE NOT NULL,
CONSTRAINT pk_Programmes PRIMARY KEY (ID)
);
CREATE TABLE Students(
id INT,
ProgrammID INT NOT NULL,
CONSTRAINT pk_Students PRIMARY KEY (ID),
FOREIGN KEY (ProgrammID) REFERENCES Programmes(ID)
);
CREATE TABLE Branches (
BranchID INT,
ProgrammID INT NOT NULL,
name VARCHAR(200) UNIQUE NOT NULL,
--program VARCHAR(200) NOT NULL,
CONSTRAINT pk_Branches PRIMARY KEY (BranchID, ProgrammID),
FOREIGN KEY (ProgrammID) REFERENCES Programmes(ID)
);
CREATE TABLE StudentsBranch (
StudentsBranchID INT,
studentID INT NOT NULL,
ProgrammID INT NOT NULL,
BranchID INT NOT NULL,
CONSTRAINT pk_StudentsBranch PRIMARY KEY (StudentsBranchID),
FOREIGN KEY (ProgrammID) REFERENCES Programmes(id),
FOREIGN KEY (studentID) REFERENCES Students(id),
FOREIGN KEY (BranchID, ProgrammID) REFERENCES Branches(BranchID, ProgrammID)
);
I have the following queries that I run to create tables in MS SQL Server:
CREATE TABLE menus
(
menu_id int NOT NULL PRIMARY KEY,
menu_name char,
other_details char
)
CREATE TABLE bookings
(
booking_Id int NOT NULL PRIMARY KEY,
date_booked DATE,
date_of_booking DATE,
other_details char,
staff_id int FOREIGN KEY REFERENCES staff(staff_id),
customer_id int FOREIGN KEY REFERENCES customers(customer_id)
)
CREATE TABLE menus_booked
(
menu_id INT NOT NULL,
booking_id INT NOT NULL,
CONSTRAINT PK_menus_booked PRIMARY KEY(menu_id,booking_id),
FOREIGN KEY (menu_id) REFERENCES menus(menu_id),
FOREIGN KEY (booking_id) REFERENCES bookings(booking_id)
)
CREATE TABLE menu_changes
(
change_id int NOT NULL PRIMARY KEY,
menu_id int NOT NULL,
booking_id int NOT NULL,
change_details char,
FOREIGN KEY (menu_id) REFERENCES menus_booked(menu_id),
FOREIGN KEY (booking_id) REFERENCES menus_booked(booking_id)
)
On running the last query I get the error:
There are no primary or candidate keys in the referenced table 'menus_booked' that match the referencing column list in the foreign key 'FK_menu_chan_menu'
I am unsure if my queries are correct and can't resolve this error.
The primary key of menus_booked is a unique combination of menu_id and booking_id. A foreign must point to that combination, not just one of its fields, which is not necessarily unique. Your query currently tries to define two foreign keys, one on each column, instead of one foreign key on the combination of the columns:
CREATE TABLE menu_changes
(
change_id int NOT NULL PRIMARY KEY,
menu_id int NOT NULL,
booking_id int NOT NULL,
change_details char,
FOREIGN KEY (menu_id, booking_id)
REFERENCES menus_booked(menu_id, booking_id) -- Here!
)
A foreign key has to reference a primary key (or unique key but here the PK is the problem), and it has to reference it in it's entirety.
FOREIGN KEY (menu_id) REFERENCES menus_booked(menu_id),
FOREIGN KEY (booking_id) REFERENCES menus_booked(booking_id)
You have two foreign key's referencing part of the primary key of menus_booked. You'll have to alter it to:
FOREIGN KEY (menu_id, booking_id) REFERENCES menus_booked(menu_id, booking_id)
Im very new to SQL and i tried to create a many to many relationship:
CREATE TABLE HOUSE_USER
(
USER_ID NUMBER(10) NOT NULL,
USER_EMAIL VARCHAR(255) NOT NULL,
USER_PASSWORD VARCHAR(255) NOT NULL,
CONSTRAINT USER_PK PRIMARY KEY(USER_ID),
CONSTRAINT PROFILE_FK FOREIGN KEY(PROFILE_ID) REFERENCES HOUSE_PROFILE(PROFILE_ID)
);
CREATE TABLE HOUSE_USER_GROUPE
(
USER_GROUPE_ID NUMBER(10) NOT NULL,
USER_GROUPE_NAME VARCHAR(255) NOT NULL,
CONSTRAINT USER_GROUPE_PK PRIMARY KEY(USER_GROUPE_ID)
);
CREATE TABLE HOUSE_USER_USER_GROUPE
(
USER_ID NUMBER(10) NOT NULL,
USER_GROUPE_ID NUMBER(10) NOT NULL,
CONSTRAINT USER_USER_GROUPE_PK PRIMARY KEY(USER_ID, USER_GROUPE_ID),
CONSTRAINT USER_FK FOREIGN KEY(USER_ID) REFERENCES HOUSE_USER(USER_ID),
CONSTRAINT USER_GROUPE_FK FOREIGN KEY(USER_GROUPE_ID) REFERENCES HOUSE_USER_GROUPE(USER_GROUPE_ID)
);
I need to ask now if these two constraints:
CONSTRAINT USER_FK FOREIGN KEY(USER_ID) REFERENCES HOUSE_USER(USER_ID),
CONSTRAINT USER_GROUPE_FK FOREIGN KEY(USER_GROUPE_ID) REFERENCES
are neccessary or not. I ask because i have another many to many relationship:
CREATE TABLE HOUSE_USER_GROUPE
(
USER_GROUPE_ID NUMBER(10) NOT NULL,
USER_GROUPE_NAME VARCHAR(255) NOT NULL,
CONSTRAINT USER_GROUPE_PK PRIMARY KEY(USER_GROUPE_ID)
);
CREATE TABLE HOUSE_ACCESSR
(
ACCESSR_ID NUMBER(10) NOT NULL,
ACCESSR_NAME VARCHAR(255) NOT NULL,
CONSTRAINT ACCESSR_PK PRIMARY KEY(ACCESSR_ID)
);
CREATE TABLE HOUSE_USER_GROUPE_ACCESR
(
USER_GROUPE_ID NUMBER(10) NOT NULL,
ACCESSR_ID NUMBER(10) NOT NULL,
CONSTRAINT USER_GROUPE_ACCESSR_PK PRIMARY KEY(USER_GROUPE_ID, ACCESSR_ID),
CONSTRAINT USER_GROUPE_FK FOREIGN KEY(USER_GROUPE_ID) REFERENCES HOUSE_USER_GROUPE(USER_GROUPE_ID),
CONSTRAINT ACCESSR_FK FOREIGN KEY(ACCESSR_ID) REFERENCES HOUSE_ACCESSR(ACCESSR_ID)
);
I cant create the second many to many table because i already used the constraint:
CONSTRAINT USER_GROUPE_FK FOREIGN KEY(USER_GROUPE_ID) REFERENCES HOUSE_USER_GROUPE(USER_GROUPE_ID),
I could just rename it but because of that error:
ORA-02264: name already used by an existing constraint
I just was wondering if these constraints are mandatory.
Yes, you should create the foreign key constrain on both tables.
The foreign key constraints are there to maintain referential integrity; ensuring that you can't insert values that don't exist in the parent table.
If you don't add the constraint to HOUSE_USER_GROUPE_ACCESR then you don't get that protection in that table. And you should want that protection everywhere.
Your only apparent mistake is that the constraint names are identical to each other. I traditionally either include No Name (letting Oracle decide on the name, because I never refer to the constraint by name) or use a format something like fk_<table>_<field>.
You need to do the constraints.. create the second constraints with another name.
I'm getting this error when trying to create a table with foreign key:
There are no primary or candidate keys in the referenced table 'TeamToPlayers' that match the referencing column list in the foreign key 'FKey2'.
I don't understand why, there is a primary key in the table TeamToPlayers.
Here are the queries:
create table TeamToPlayers
(TeamName varchar(50) NOT NULL,
PlayerName varchar(50) NOT NULL,
primary key(TeamName,PlayerName),
CONSTRAINT FKey FOREIGN KEY (TeamName) REFERENCES Teams(TeamName)
)
create table Players
(PlayerName varchar(50) NOT NULL,
primary key(PlayerName),
CONSTRAINT FKey2 FOREIGN KEY (PlayerName) REFERENCES TeamToPlayers(PlayerName)
);
Table TeamToPlayers primary key consists of two fields - you must reference both as otherwise it's not a key. I think you may have your key the wrong way round - it should be on TeamToPlayers and referencing Players like so:
create table TeamToPlayers
(
TeamName varchar(50) NOT NULL,
PlayerName varchar(50) NOT NULL,
primary key(TeamName,PlayerName),
CONSTRAINT FKey FOREIGN KEY (TeamName) REFERENCES Teams(TeamName),
CONSTRAINT FKey2 FOREIGN KEY (PlayerName) REFERENCES Players(PlayerName)
)
create table Players
(PlayerName varchar(50) NOT NULL,
primary key(PlayerName),
);