An error message regarding indexes displays when foreign keys are added using the following scripts. I have added primary keys and indexes different ways but not sure if the diagram is providing information about how to setup the indexes/primary keys that I'm not seeing.
CREATE TABLE aocommercial_building(
parcel CHAR(25) NOT NULL,
suffix INT NOT NULL,
owner VARCHAR(255) NULL,
owner2 VARCHAR(255) NULL,
);
CREATE TABLE aocommercial_heatcool(
parcel CHAR(25) NOT NULL,
suffix INT NOT NULL,
section INT NULL,
heat_cool_cd VARCHAR(255) NULL
);
CREATE TABLE aocommercial_unit(
parcel CHAR(25) NOT NULL,
suffix INT NOT NULL,
section INT NOT NULL,
occ_desc VARCHAR(255) NULL
);
CREATE TABLE aocom_misc_bldg(
parcel CHAR(25) NOT NULL,
suffix INT NOT NULL,
section INT NOT NULL,
misc_bldg_type VARCHAR(255) NULL
);
ALTER TABLE aocommercial_unit ADD FOREIGN KEY (parcel) REFERENCES aocommercial_building(parcel);
ALTER TABLE aocommercial_unit ADD FOREIGN KEY (suffix) REFERENCES aocommercial_building(suffix);
ALTER TABLE aocommercial_heatcool ADD FOREIGN KEY (parcel) REFERENCES aocommercial_unit(parcel);
ALTER TABLE aocommercial_heatcool ADD FOREIGN KEY (suffix) REFERENCES aocommercial_unit(suffix);
ALTER TABLE aocommercial_heatcool ADD FOREIGN KEY (section) REFERENCES aocommercial_unit(section);
ALTER TABLE aocom_misc_bldg ADD FOREIGN KEY (parcel) REFERENCES aocommercial_unit(parcel);
ALTER TABLE aocom_misc_bldg ADD FOREIGN KEY (suffix) REFERENCES aocommercial_unit(suffix);
ALTER TABLE aocom_misc_bldg ADD FOREIGN KEY (section) REFERENCES aocommercial_unit(section);
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For each table, what column (or combination of columns) uniquely identifies each row? Then, include in each CREATE TABLE another line with PRIMARY KEY(...).
For each table, if there is no particular set of columns to uniquely define each row, then add
id INT UNSIGNED NOT NULL AUTO_INCREMENT,
PRIMARY KEY(id)
Look around; there are lots and lots of examples.
Related
so I have written this Mariadb code as the solution for an assignment and am running it on HeidiSQL. It should work in theory however I am getting the error message SQL Error (1005): Can't create table bestellung.arbeitetin (errno: 150 "Foreign key constraint is incorrectly formed"). Upon using show warning, the program elaborates that "referenced table bestellung.arbeitetin not found in the data dictionary". I am wondering, is there something wrong with the code?
Datum date not NULL,
Abholtermin DATE,
Kostenstelle int not NULL,
Abteilung char(5) not NULL,
Mitarbeiter int not NULL,
Telefon int not NULL,
primary key (Bestellnummer)
);
create table enthaelt (
FK_Bestellnummer int not NULL,
FK_Artikelnummer char(10) not NULL,
Menge int not NULL,
unique key (FK_Bestellnummer, FK_Artikelnummer)
);
alter table enthaelt ADD
constraint FK_ArtikelNr
foreign key (FK_Artikelnummer)
references Artikel (Artikelnummer);
alter table enthaelt ADD
constraint FK_BestellNr
foreign key (FK_Bestellnummer)
references Bestellung (Bestellnummer);
create table arbeitetin
(
FK_PersNr int not NULL,
FK_ProjektNr int not NULL,
unique key(FK_PersNr, FK_ProjektNr)
);
alter table arbeitetin ADD
constraint FK_ARBEITETIN_MITARBEITER1
FOREIGN KEY (FK_PersNr)
REFERENCES Mitarbeiter (PersNr);
alter table arbeitetin ADD
constraint FK_ARBEITETIN_PROJEKT
foreign key (FK_ProjektNr)
references Projekt (ProjektNr);
alter table Mitarbeiter ADD
constraint FK_MITARBEITER_ABTEILUNG
foreign key (FK_Abkuerzung)
references Abteilung (Abkuerzung); ```
CREATE TABLE public.impiegato(
CF varchar NOT NULL,
codice_reparto int4 NOT NULL,
mansione varchar NULL,
CONSTRAINT impiegato_pkey PRIMARY KEY (CF),
CONSTRAINT impiegato_fkey FOREIGN KEY (codice_reparto) REFERENCES reparto(codice),
);
CREATE TABLE public.reparto(
codice int4 NOT NULL,
nome varchar NULL,
cf_responsabile varchar NULL,
nome_responsabile varchar NULL UNIQUE,
CONSTRAINT reparto_pkey PRIMARY KEY (codice),
CONSTRAINT reparto_cf_responsabile_fkey FOREIGN KEY (cf_responsabile) REFERENCES impiegato(CF)
);
When i run the sql code it tells me that the impiegato table doesn't exist. Can I run a foreign key on a primary key of another table?
The referenced table must exists when a foreign key is declared.
Since in your case the two tables reference each other, it's not possible to solve this by simply creating the right one first.
You have to create the first one (any of them) first without the foreign key constraint, create the second on and then add the foreign key constraint to the first one.
Something along the lines of:
CREATE TABLE public.impiegato
(cf varchar
NOT NULL,
codice_reparto int4
NOT NULL,
mansione varchar
NULL,
CONSTRAINT impiegato_pkey
PRIMARY KEY (cf));
CREATE TABLE public.reparto
(codice int4
NOT NULL,
nome varchar
NULL,
cf_responsabile varchar
NULL,
nome_responsabile varchar
NULL
UNIQUE,
CONSTRAINT reparto_pkey
PRIMARY KEY (codice),
CONSTRAINT reparto_cf_responsabile_fkey
FOREIGN KEY (cf_responsabile)
REFERENCES impiegato
(cf));
ALTER TABLE public.impiegato
ADD CONSTRAINT impiegato_fkey
FOREIGN KEY (codice_reparto)
REFERENCES reparto
(codice);
Unfortunately, you didn't tag your DBMS. From some details I guessed it might be Postgres and the code above hence is Postgres code. If you don't use Postgres, you might need to adapt the ALTER TABLE statement, they can differ between DBMS.
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 am starting to build something like system up to the just cooperate with suggestions coming into the database called ForslagOpslag.
Every time I try to update table with likes, you will see it with this one error:
Update cannot proceed due to validation errors. Please correct the following errors and try again.
SQL71516 :: The referenced table '[dbo].[ForslagOpslag]' contains no
primary or candidate keys that match the referencing column list in
the foreign key. If the referenced column is a computed column, it
should be persisted.
Here is how I built my ForslagOpslagLikes table:
CREATE TABLE [dbo].[ForslagOpslagLikes]
(
[fk_brugerid] INT NOT NULL,
[opretdato] DATETIME NOT NULL,
[getid] INT NOT NULL,
CONSTRAINT [PK_ForslagOpslagLikes]
PRIMARY KEY CLUSTERED ([fk_brugerid], [getid]),
CONSTRAINT [FK_ForslagOpslagLikes_ToGetid]
FOREIGN KEY ([getid])
REFERENCES [dbo].[ForslagOpslag]([Id]),
CONSTRAINT [FK_ForslagOpslagLikes_ToForslagBrugerid]
FOREIGN KEY ([fk_brugerid])
REFERENCES [dbo].[ForslagOpslag]([fk_brugerid])
);
Reason I have both fk_brugerid and getid is for sure me that the user can not vote / like more once!
The way I have built my ForslagOpslag table:
CREATE TABLE [dbo].[ForslagOpslag]
(
[Id] INT IDENTITY (1, 1) NOT NULL,
[text] NVARCHAR (MAX) NOT NULL,
[fk_brugerid] INT NOT NULL,
[opretdato] DATETIME NOT NULL,
PRIMARY KEY CLUSTERED ([Id] ASC)
);
like this to be my like system do:
ForslagOpslagLikes -> fk_brugerid to ForslagOpslag -> fk_brugerid
ForslagOpslagLikes -> getid to ForslagOpslag -> id
Well - the error seems pretty clear: you're trying to estabslish a foreign key relationship to ForslagOpslag.fk_brugerid here:
CONSTRAINT [FK_ForslagOpslagLikes_ToForslagBrugerid]
FOREIGN KEY ([fk_brugerid])
REFERENCES [dbo].[ForslagOpslag]([fk_brugerid])
but that column is NOT the primary key of that other table - and it's not a UNIQUE constraint either - so you cannot reference that column in a foreign key relationship.
But the column(s) that a foreign key references must be the primary key of that other table - or in SQL Server, it's good enough if there's a UNIQUE constraint on that column. You must ensure that the values you reference in FroslagOpslag only match a single column in that table - otherwise, you cannot establish a foreign key relationship
Try to remove the foreing key in your first table like this
CREATE TABLE [dbo].[ForslagOpslagLikes]
(
[fk_brugerid] INT NOT NULL,
[opretdato] DATETIME NOT NULL,
[getid] INT NOT NULL,
CONSTRAINT [PK_ForslagOpslagLikes]
PRIMARY KEY CLUSTERED ([fk_brugerid], [getid]),
CONSTRAINT [FK_ForslagOpslagLikes_ToGetid]
FOREIGN KEY ([getid])
REFERENCES [dbo].[ForslagOpslag]([Id]),
);
Then you need to add the foreign key in the second table with the primary key with the first table
CREATE TABLE [dbo].[ForslagOpslag]
(
[Id] INT IDENTITY (1, 1) NOT NULL,
[text] NVARCHAR (MAX) NOT NULL,
[fk_brugerid] INT NOT NULL,
[opretdato] DATETIME NOT NULL,
PRIMARY KEY CLUSTERED ([Id] ASC),
CONSTRAINT [FK_ForslagOpslagLikes_ToForslagBrugerid]
FOREIGN KEY ([fk_brugerid])
REFERENCES [dbo].[ForslagOpslagLikes]([fk_brugerid])
);
You sound scandinavian, and Bruger means User (for all the non-scandinavians here).
What you appear to want is a Bruger (User) table, where fk_brugerid in ForslagOpslag is the user who created the record with opretdato being the creation date, and ForslagOpslagLikes is an association table of users who likes the ForslagOpslag with opretdato being the date they clicked on "Like".
CREATE TABLE [dbo].[Bruger]
(
[brugerid] INT IDENTITY (1, 1) NOT NULL,
...,
CONSTRAINT [PK_Bruger]
PRIMARY KEY CLUSTERED ([brugerid])
);
CREATE TABLE [dbo].[ForslagOpslag]
(
[Id] INT IDENTITY (1, 1) NOT NULL,
[text] NVARCHAR(MAX) NOT NULL,
[fk_brugerid] INT NOT NULL,
[opretdato] DATETIME NOT NULL,
CONSTRAINT [PK_ForslagOpslag]
PRIMARY KEY CLUSTERED ([Id]),
CONSTRAINT [FK_ForslagOpslag_Bruger]
FOREIGN KEY ([fk_brugerid])
REFERENCES [dbo].[Bruger] ([brugerid])
);
CREATE TABLE [dbo].[ForslagOpslagLikes]
(
[fk_brugerid] INT NOT NULL,
[opretdato] DATETIME NOT NULL,
[getid] INT NOT NULL,
CONSTRAINT [PK_ForslagOpslagLikes]
PRIMARY KEY CLUSTERED ([fk_brugerid], [getid]),
CONSTRAINT [FK_ForslagOpslagLikes_Bruger]
FOREIGN KEY ([fk_brugerid])
REFERENCES [dbo].[Bruger] ([brugerid]),
CONSTRAINT [FK_ForslagOpslagLikes_ForslagOpslag]
FOREIGN KEY ([getid])
REFERENCES [dbo].[ForslagOpslag]([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.