Hi this is the table I am trying to create:
CREATE TABLE images
(
id PRIMARY KEY NOT NULL INT,
product_id FOREIGN KEY NOT NULL INT,
src varchar(255) NOT NULL
)
But its not letting me (I am getting a syntax error). Anyone have any ideas?
CREATE TABLE IMAGES(
Id int NOT NULL,
PRODUCT_ID int NOT NULL,
src varchar(255) NOT NULL,
PRIMARY KEY (Id),
FOREIGN KEY (P_Id) REFERENCES PRODUCTS(P_Id)
)
and make sure you build the Products table first , and do the reference foreign key
Check out InnoDB Foreign Key Constraints for the right syntax to use. In particular, you need to declare the column you're referencing when you create a foreign key.
Additionally, since you're using MySQL, make sure your tables use InnoDB, otherwise the foreign keys won't actually get enforced.
Related
I have two table
CREATE TABLE `abc` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`ref_id` varchar(20) NOT NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `ref_id_UNIQUE` (`ref_id`)
)
CREATE TABLE `xyz` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`ref_id` varchar(20) DEFAULT NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `ref_id_UNIQUE` (`ref_id`)
)
I want to make foreign key relation ship between xyz's ref_id and abc's ref_id .But Mysql gives error 1215.
You should make the foreign key relationships to the primary keys. I know that MySQL allows foreign key relationships to anything with an index. But the correct practice is to use primary keys.
So declare the table like this:
CREATE TABLE `xyz` (
`id` int(11) NOT NULL AUTO_INCREMENT,
abc_id int DEFAULT NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `ref_id_UNIQUE` (`abc_id`),
ADD CONSTRAINT fk_xyz_abc FOREIGN KEY (abc_id) REFERENCES abc(id)
);
If you want the ref_id for an xyz row, then use JOIN to get the information.
Take a look at Gordon Linoff's answer, his suggestion makes sense, even though it does not answer the question. So what can cause an error when you intend to create a foreign key relationship? The obvious possibility is syntax error and typo, so you will need to check against those and fix any such problems.
Another possibility is that you have inconsistency, that is, you try to create a foreign key constraint in one of your tables, but not all the values have exact matches. So, assuming that you have Foo and Bar table and you intend Foo.lorem to be a foreign key referencing Bar.ipsum, then you will need to ensure that all the values you have for Foo.lorem has a Bar.ipsum pair with the exact same values (except null). If that's not true, then your foreign key constraint will not be successfully created. Find such inconsistencies:
select distinct Foo.lorem
from Foo
where not (Foo.lorem is null) and
not exists (select 1 from Bar where Foo.lorem = Bar.ipsum);
Read the lines carefully and make sure you fix any such Foo.lorem values.
I have created 2 tables with a parent child relationship in MYSQL. However, the foreign key relationship fails with error code 1215. The MAIN_ROLE can have many SUB_ROLE aliases. The SUB_ROLE has a composite PRIMARY key (ID,MAIN_ID,SEQ_NUM). The MAIN_ROLE table's PRIMARY KEY is part of SUB_ROLES primary key.
Here are the tables and my constraints:
create TABLE MAIN_ROLE(
ID int NOT NULL AUTO_INCREMENT,
MAIN_ID int NOT NULL,
ASSIGNED_DATE datetime NULL,
MAIN_ROLE_NM varchar(50) NOT NULL,
PRIMARY KEY(ID,MAIN_ID)
);
create TABLE SUB_ROLE(
ID int NOT NULL,
MAIN_ID int NOT NULL,
SEQ_NUM decimal(15, 0) NOT NULL,
SUB_ROLE_NM varchar(50) NOT NULL,
PRIMARY KEY(ID,MAIN_ID,SEQ_NUM) ,
CONSTRAINT SUB_ROLE_FK REFERENCES MAIN_ROLE(ID,MAIN_ID,SEQ_NUM)
);
Could someone point out what's wrong with the foreign key in my scripts? Please help!
The main problem is that you are not following mysql's foreign key syntax and that you a referencing a field in the parent table that is not there:
You do not provide a list of fields from the child table
SEQ_NUM field does not exist in the main table, only in the sub table.
Correct foreign key definition would look like as follows:
CONSTRAINT SUB_ROLE_FK FOREIGN KEY (ID,MAIN_ID) REFERENCES MAIN_ROLE(ID,MAIN_ID)
However, I do not really see ehat's the point of having an auto increment id field and a main_id field in the main table. I would take a 2nd look at that.
This worked, CONSTRAINT SUB_ROLE_FK FOREIGN KEY (ID,MAIN_ID) REFERENCES MAIN_ROLE(ID,MAIN_ID)
I am trying to create a reference in mysql using primary and foriegn key reference but it is not showing
db
this is the schema of my database
[CREATE TABLE fname(
id INT PRIMARY KEY AUTO_INCREMENT,
fname VARCHAR(29))
CREATE TABLE parent(
p_id INT PRIMARY KEY AUTO_INCREMENT,
id INT,
FOREIGN KEY(id) REFERENCES fname(id)
)
From what I've read in a comment to a remove answer, you want to insert a value in parent and have it automatically available in fname. This is not the way a foreign key is working. Foreign keys will only allow values in parent which already (meaning before the insert) exist in fname.
If this is not what you want, than please explain your problem in more detail.
CREATE TABLE fname(
id INT PRIMARY KEY AUTO_INCREMENT,
fname VARCHAR(29));
CREATE TABLE parent(
p_id INT PRIMARY KEY AUTO_INCREMENT,
id INT,
CONSTRAINT `fk11`
FOREIGN KEY (`id`)
REFERENCES `fname` (`id`)
);
Ref: https://dev.mysql.com/doc/refman/5.5/en/create-table-foreign-keys.html
PS: Although SO is a community of people ready to help, it is always good to have a look at the docs or do a simple web search before asking a question here.
i got these two succesfull queries:
create table Donors (
donor_id int not null auto_increment primary key,
gender varchar(1) not null,
date_of_birth date not null,
first_name varchar(20) not null,
middle_name varchar(20),
last_name varchar(30) not null,
home_phone tinyint(10),
work_phone tinyint(10),
cell_mobile_phone tinyint(10),
medical_condition text,
other_details text );
and
create table Donors_Medical_Condition (
donor_id int not null,
condition_code int not null,
seriousness text,
primary key(donor_id, condition_code),
foreign key(donor_id) references Donors(donor_id) );
but when i try this one:
create table Medical_Conditions (
condition_code int not null,
condition_name varchar(50) not null,
condition_description text,
other_details text,
primary key(condition_code),
foreign key(condition_code) references Donors_Medical_Condition(condition_code) );
i get "Error Code: 1215, cannot add foreign key constraint"
i dont know what am i doing wrong.
In MySql, a foreign key reference needs to reference to an index (including primary key), where the first part of the index matches the foreign key field. If you create an an index on condition_code or change the primary key st that condition_code is first you should be able to create the index.
To define a foreign key, the referenced parent field must have an index defined on it.
As per documentation on foreign key constraints:
REFERENCES tbl_name (index_col_name,...)
Define an INDEX on condition_code in parent table Donors_Medical_Condition and it should be working.
create table Donors_Medical_Condition (
donor_id int not null,
condition_code int not null,
seriousness text,
KEY ( condition_code ), -- <---- this is newly added index key
primary key(donor_id, condition_code),
foreign key(donor_id) references Donors(donor_id) );
But it seems you defined your tables order and references wrongly.
You should have defined foreign key in Donors_Medical_Condition table but not in Donors_Medical_Conditions table. The latter seems to be a parent.
Modify your script accordingly.
They should be written as:
-- create parent table first ( general practice )
create table Medical_Conditions (
condition_code int not null,
condition_name varchar(50) not null,
condition_description text,
other_details text,
primary key(condition_code)
);
-- child table of Medical_Conditions
create table Donors_Medical_Condition (
donor_id int not null,
condition_code int not null,
seriousness text,
primary key(donor_id, condition_code),
foreign key(donor_id) references Donors(donor_id),
foreign key(condition_code)
references Donors_Medical_Condition(condition_code)
);
Refer to:
MySQL Using FOREIGN KEY Constraints
[CONSTRAINT [symbol]] FOREIGN KEY
[index_name] (index_col_name, ...)
REFERENCES tbl_name (index_col_name,...)
[ON DELETE reference_option]
[ON UPDATE reference_option]
reference_option:
RESTRICT | CASCADE | SET NULL | NO ACTION
A workaround for those who need a quick how-to:
FYI: My issue was NOT caused by the inconsistency of the columns’ data types/sizes, collation or InnoDB storage engine.
How to:
Download a MySQL workbench and use it’s GUI to add foreign key. That’s it!
Why:
The error DOES have something to do with indexes. I learned this from the DML script automatically generated by the MySQL workbench. Which also helped me to rule out all those inconsistency possibilities.It applies to one of the conditions to which the foreign key definition subject. That is: “MySQL requires indexes on foreign keys and referenced keys so that foreign key checks can be fast and not require a table scan.” Here is the official statement: http://dev.mysql.com/doc/refman/5.7/en/create-table-foreign-keys.html
I did not get the idea of adding an index ON the foreign key column(in the child table), only paid attention to the referenced TO column(in the parent table).
Here is the auto-generated script(PHONE.PERSON_ID did not have index originally):
ALTER TABLE `netctoss`.`phone`
ADD INDEX `personfk_idx` (`PERSON_ID` ASC);
ALTER TABLE `netctoss`.`phone`
ADD CONSTRAINT `personfk`
FOREIGN KEY (`PERSON_ID`)
REFERENCES `netctoss`.`person` (`ID`)
ON DELETE NO ACTION
ON UPDATE NO ACTION;
I think you've got your tables a bit backwards. I'm assuming that Donors_Medical_Condtion links donors and medical conditions, so you want a foreign key for donors and conditions on that table.
UPDATED
Ok, you're also creating your tables in the wrong order. Here's the entire script:
create table Donors (
donor_id int not null auto_increment primary key,
gender varchar(1) not null,
date_of_birth date not null,
first_name varchar(20) not null,
middle_name varchar(20),
last_name varchar(30) not null,
home_phone tinyint(10),
work_phone tinyint(10),
cell_mobile_phone tinyint(10),
medical_condition text,
other_details text );
create table Medical_Conditions (
condition_code int not null,
condition_name varchar(50) not null,
condition_description text,
other_details text,
primary key(condition_code) );
create table Donors_Medical_Condition (
donor_id int not null,
condition_code int not null,
seriousness text,
primary key(donor_id, condition_code),
foreign key(donor_id) references Donors(donor_id),
foreign key(condition_code) references Medical_Conditions(condition_code) );
I got the same issue and as per given answers, I verified all datatype and reference but every time I recreate my tables I get this error. After spending couple of hours I came to know below command which gave me inside of error-
SHOW ENGINE INNODB STATUS;
LATEST FOREIGN KEY ERROR
------------------------
2015-05-16 00:55:24 12af3b000 Error in foreign key constraint of table letmecall/lmc_service_result_ext:
there is no index in referenced table which would contain
the columns as the first columns, or the data types in the
referenced table do not match the ones in table. Constraint:
,
CONSTRAINT "fk_SERVICE_RESULT_EXT_LMC_SERVICE_RESULT1" FOREIGN KEY ("FK_SERVICE_RESULT") REFERENCES "LMC_SERVICE_RESULT" ("SERVICE_RESULT") ON DELETE NO ACTION ON UPDATE NO ACTION
I removed all relation using mysql workbench but still I see same error. After spending few more minutes, I execute below statement to see all constraint available in DB-
select * from information_schema.table_constraints where
constraint_schema = 'XXXXX'
I was wondering that I have removed all relationship using mysql workbench but still that constraint was there. And the reason was that because this constraint was already created in db.
Since it was my test DB So I dropped DB and when I recreate all table along with this table then it worked. So solution was that this constraint must be deleted from DB before creating new tables.
Check that both fields are the same size and if the referenced field is unsigned then the referencing field should also be unsigned.
im new on mysql workbench, and i tried so many things to put my script working but i simply cant... Ive got these tables:
CREATE TABLE Utilizador (email varchar(40) not null, nome varchar(50)
not null, dataNascimento date, profissao varchar(50) not null,
reputacao double(3,2) unsigned not null, constraint pk_Utilizador
primary key(email))
This is the first table created!
CREATE TABLE POI (email varchar(40) not null, designacaoPOI
varchar(10) not null, coordenadaX int, coordenadaY int,
descricaoPOI varchar(200), constraint pk_POI primary key(email,
designacaoPOI), constraint fk_POI foreign key(email) references
Utilizador(email) on delete cascade)
This is the second table created!
CREATE TABLE Utilizador_POI (email varchar(40) not null, designacaoPOI
varchar(10) not null, constraint pk_Utilizador_POI primary key(email,
designacaoPOI), constraint fk1_Utilizador_POI foreign key(email)
references Utilizador(email) on delete cascade, constraint
fk2_Utilizador_POI foreign key(designacaoPOI) references
POI(designacaoPOI) on delete cascade)
This table gives me the error: Error Code: 1215. Cannot add foreign key constraint
I did some tests and im almost sure that the problem is in the foreign key "designacaoPOI". The other FK ("email") dont give me any error, so maybe the problem is in the Table POI?
Thanks in advanced!
The problem here is twofold:
1/ Use IDs for PRIMARY KEYs
You should be using IDs for primary keys rather than VARCHARs or anything that has any real-world "business meaning". If you want the email to be unique within the Utilizador table, the combination of email and designacaoPOI to be unique in the POI table, and the same combination (email and designacaoPOI) to be unique in Utilizador_POI, you should be using UNIQUE KEY constraints rather than PRIMARY KEY constraints.
2/ You cannot DELETE CASCADE on a FOREIGN KEY that doesn't reference the PRIMARY KEY
In your third table, Utilizador_POI, you have two FOREIGN KEYs references POI. Unfortunately, the PRIMARY KEY on POI is a composite key, so MySQL has no idea how to handle a DELETE CASCADE, as there is not a one-to-one relationship between the FOREIGN KEY in Utilizador_POI and the PRIMARY KEY of POI.
If you change your tables to all have a PRIMARY KEY of ID, as follows:
CREATE TABLE blah (
id INT(9) AUTO_INCREMENT NOT NULL
....
PRIMARY KEY (id)
);
Then you can reference each table by ID, and both your FOREIGN KEYs and DELETE CASCADEs will work.
I think the problem is that Utilizador_POI.email references POI.email, which itself references Utilizador.email. MySQL is probably upset at the double-linking.
Also, since there seems to be a many-to-many relationship between Utilizador and POI, I think the structure of Utilizador_POI isn't what you really want. Instead, Utilizador_POI should reference a primary key from Utilizador, and a matching primary key from POI.
The problem is in your second table. Your primary key is (email,designacaoPOI), when you try to reference that in your table it gives you error because of this:
InnoDB permits a foreign key to reference any index column or group of
columns. However, in the referenced table, there must be an index
where the referenced columns are listed as the first columns in the
same order.
For it to work, either change the order of your second tale PRIMARY KEY :
CREATE TABLE POI (
email VARCHAR(40) NOT NULL,
designacaoPOI VARCHAR(10) NOT NULL,
coordenadaX INT,
coordenadaY INT,
descricaoPOI VARCHAR(200),
CONSTRAINT pk_POI PRIMARY KEY (designacaoPOI,email), -- changed the order
CONSTRAINT fk_POI FOREIGN KEY (email)
REFERENCES Utilizador(email) ON DELETE CASCADE
);
sqlfiddle demo
or add an index for designacaoPOI:
CREATE TABLE POI (
email VARCHAR(40) NOT NULL,
designacaoPOI VARCHAR(10) NOT NULL,
coordenadaX INT,
coordenadaY INT,
descricaoPOI VARCHAR(200),
CONSTRAINT pk_POI PRIMARY KEY (designacaoPOI,email),
KEY key_designacaoPOI(designacaoPOI), -- added index for that column
CONSTRAINT fk_POI FOREIGN KEY (email)
REFERENCES Utilizador(email) ON DELETE CASCADE
);
sqlfiddle demo
Either of these solutions will let you create your third table without errors.