I am getting the above error when I execute the following query.
CREATE TABLE doctor
(
id varchar(6) NOT NULL,
Specialization varchar(15) NOT NULL,
FOREIGN KEY(id) REFERENCES employee(id)
on delete cascade on update cascade
);
Where is the problem?
You need an index on employee(id) and before you add any FK pointing at it. You also need one on doctor(id). In both cases, a primary key seems like a good option.
Don't forget that in the CREATE TABLE script, the PRIMARY KEY should appear before the FOREIGN KEY instruction.
See this post for a quick how-to: How to add a primary key to a MySQL table?
Related
I cannot seem to be able to delete primary keys in a table.
All references (FKs) have been removed but it still doesn't let me delete it.
What I'm trying to do is: delete old primary keys to add a new one - but keep the old columns and data (just remove the PK attribute).
What is wrong ?
Table:
CREATE TABLE `employee` (
`User` int(10) unsigned NOT NULL,
`Company` int(10) unsigned NOT NULL,
--unrelated boolean fields
PRIMARY KEY (`User`,`Company`),
KEY `FK_Employee_Company_idx` (`Company`),
CONSTRAINT `FK_Employee_Company` FOREIGN KEY (`Company`) REFERENCES `company` (`ID`) ON DELETE NO ACTION ON UPDATE NO ACTION,
CONSTRAINT `FK_Employee_User` FOREIGN KEY (`User`) REFERENCES `user` (`ID`) ON DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
Trying to delete:
alter table Employee
drop primary key;
Issue:
Error 1025: Error on rename of '.\DB_NAME#sql-3640_4' to '.\DB_NAME\employee' (errno: 150 "Foreign key constraint is incorrectly formed") SQL Statement: ALTER TABLE DB_NAME.employee DROP PRIMARY KEY
Nothing references this table anymore. I also checked via statements which select from information_schema.key_column_usage but yields no results.
Wasted the last hours on Google but can't seem to figure it out.
And if that would work, adding a new column:
alter table Employee
add column ID int unsigned not null auto_increment primary key;
The index is still needed for the existing FK constraints.
Adding the following index (first) should satisfy that requirement:
CREATE INDEX xxx ON employee (User, Company);
Test case
I have a database, I used these commands :
CREATE TABLE APPOINTMENT (app_id INT(5) NOT NULL, app_doctor INT(5) NOT NULL, app_date DATE, PRIMARY KEY (app_id));
CREATE TABLE APPPATIENTS (patient_ssn INT(10) NOT NULL, patient_name VARCHAR(20) NOT NULL, sex CHAR(1) NOT NULL, appointment_id INT(5), PRIMARY KEY (patient_ssn), UNIQUE (appointment_id));
ALTER TABLE APPPATIENTS ADD FOREIGN KEY (appointment_id) REFERENCES APPOINTMENT(app_id) ON DELETE CASCADE;
Now, I want to delete foreign key appointment_id in appPatients table :
ALTER TABLE apppatients DROP FOREIGN KEY appointment_id;
But I got an error :
Can't drop 'appointment_id'; check that column/key exists.
It is there! How can it give that error? What am I doing wrong?
I tried to create a database with your code and I notice the foreign key name appears different from appointment_id: reading with more attention the command definition, I notice that when you write
ADD FOREIGN KEY (appointment_id)
you are only saying the column on which the constraint will be created, not its name.
You can read the specifications here:
SQL FOREIGN KEY Constraint on ALTER TABLE
So, if you want to specify the name of the key, you have to write, for example:
alter table APPPATIENTS
ADD CONSTRAINT appointment_key
FOREIGN KEY (appointment_id)
REFERENCES appointment(app_id) ON DELETE CASCADE;
And so you know the name of the foreign key you created (appointment_key in this case).
If you want to know the foreign key name generated by mysql you can use the command
show create table APPPATIENTS;
that shows the complete table definition.
I create a table in mysql using the following script:
CREATE TABLE IF NOT EXISTS users_x_activities(
id int NOT NULL auto_increment,
id_user int unsigned NOT NULL,
id_attivita int unsigned NOT NULL,
PRIMARY KEY (id),
FOREIGN KEY (id_user) REFERENCES utente(id),
FOREIGN KEY (id_attivita) REFERENCES attivita(id)
) ENGINE = INNODB;
When I export the created table from phpMyAdmin, I obtain the following script
CREATE TABLE IF NOT EXISTS `users_x_activities` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`id_user` int(10) unsigned NOT NULL,
`id_attivita` int(10) unsigned NOT NULL,
PRIMARY KEY (`id`),
KEY `id_user` (`id_user`),
KEY `id_attivita` (`id_attivita`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=1 ;
So the question are: where is my foreign key constraints? does KEY refer to FK? Seems that the two tables utente and attivita are no longer referenced in the new generated script. where am I doing wrong?
EDIT
In phpMyAdmin, configuring the export of the table I found the option "Display Foreign Key Relationship"
If I flag this option I otain also this code in the script
--
-- RELATIONS FOR TABLE `users_x_activity`:
-- `id_user`
-- `utente` -> `id`
-- `id_attivita`
-- `attivita` -> `id`
--
--
-- Constraints for dumped tables
--
--
-- Constraints for table `users_x_activity`
--
ALTER TABLE `users_x_activity`
ADD CONSTRAINT `users_x_activities_ibfk_1` FOREIGN KEY (`id_user`) REFERENCES `utente` (`id`),
ADD CONSTRAINT `users_x_activities_ibfk_2` FOREIGN KEY (`id_attivita`) REFERENCES `attivita` (`id`);
This means that if I add the option "Display Foreign Key Relationship" I obtain also the FK constrains? in other case not?
So the question are: where is my foreign key constraints?
They are defined in the database. The output from SHOW CREATE TABLE users_x_activities will include the foreign key constraint definitions.
The definitions of the foreign key constraints likely appear in separate ALTER TABLE statements at the end of the generated script.
does KEY refer to FK?
No. KEY id_user (id_user) here refers to an index.
Seems that the two tables utente and attivita are no longer referenced in the new generated script.
Yes, you are correct. The foreign key constraints are not included in the CREATE TABLE statement.
where am I doing wrong?
A MySQL SHOW CREATE TABLE users_x_activities will include the foreign key constraints.
The foreign key constraints are likely included in the script generated by phpMyAdmin, but at the end of the script, in separate ALTER TABLE statements.
There are two type of constraints when you managing your tables with phpmyadmin:
internal: when you set constraints with phpmyadmin designer for example the constraints stored as internal,that will not be included in export.
innoDB: these constraints included in export check out linked video about it
Setting up a foreign key constraint
Follow the following steps :
phpmyadmin configuration
export time customer configuration
I'm not sure what I'm doing wrong here, but I get an error:
Error Code: 1005. Can't create table 'erm.section' (emo:150)
Here is the code. The 'course' table is created successfully. I tried modifying the name of the course_number attritube in the 'section' table but that didn't work.
USE erm;
CREATE TABLE course
(
course_name VARCHAR(30) NOT NULL,
course_number VARCHAR(20) NOT NULL,
credit_hours INT NOT NULL,
department VARCHAR(10),
CONSTRAINT course_pk PRIMARY KEY (course_name)
);
CREATE TABLE section
(
section_identifier INT NOT NULL,
course_number VARCHAR(20),
semester VARCHAR(10) NOT NULL,
school_year VARCHAR(4) NOT NULL,
instructor VARCHAR(25),
CONSTRAINT section_pk PRIMARY KEY (section_identifier),
CONSTRAINT section_fk FOREIGN KEY (course_number)
REFERENCES course (course_number)
ON DELETE SET NULL
ON UPDATE CASCADE
);
course_number is not a primary key in the table course.
the foreign key in the table section must reference a primary key form another table.
You have to create an index on the column referenced by the foreign key:
alter table course add index (course_number);
(It doesn't have to be a primary key index.) From the MySQL documentation:
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.
A FOREIGN KEY in one table points to a PRIMARY KEY in another table.
AFAIK, dropping the CONSTRAINT, then rename, then add the CONSTRAINT back is the only way. Backup first!
to drop it use this
ALTER TABLE section
DROP FOREIGN KEY course_number
and to add it again use this
ALTER TABLE section
ADD FOREIGN KEY (course_number)
REFERENCES course (course_number)
I want to add a Foreign Key to a table called "katalog".
ALTER TABLE katalog
ADD CONSTRAINT `fk_katalog_sprache`
FOREIGN KEY (`Sprache`)
REFERENCES `Sprache` (`ID`)
ON DELETE SET NULL
ON UPDATE SET NULL;
When I try to do this, I get this error message:
Error Code: 1005. Can't create table 'mytable.#sql-7fb1_7d3a' (errno: 150)
Error in INNODB Status:
120405 14:02:57 Error in foreign key constraint of table
mytable.#sql-7fb1_7d3a:
FOREIGN KEY (`Sprache`)
REFERENCES `Sprache` (`ID`)
ON DELETE SET NULL
ON UPDATE SET NULL:
Cannot resolve table name close to:
(`ID`)
ON DELETE SET NULL
ON UPDATE SET NULL
When i use this query it works, but with wrong "on delete" action:
ALTER TABLE `katalog`
ADD FOREIGN KEY (`Sprache` ) REFERENCES `sprache` (`ID` )
Both tables are InnoDB and both fields are "INT(11) not null". I'm using MySQL 5.1.61. Trying to fire this ALTER Query with MySQL Workbench (newest) on a MacBook Pro.
Table Create Statements:
CREATE TABLE `katalog` (
`ID` int(11) unsigned NOT NULL AUTO_INCREMENT,
`Name` varchar(50) COLLATE utf8_unicode_ci NOT NULL,
`AnzahlSeiten` int(4) unsigned NOT NULL,
`Sprache` int(11) NOT NULL,
PRIMARY KEY (`ID`),
UNIQUE KEY `katalogname_uq` (`Name`)
) ENGINE=InnoDB AUTO_INCREMENT=12 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci ROW_FORMAT=DYNAMIC$$
CREATE TABLE `sprache` (
`ID` int(11) NOT NULL AUTO_INCREMENT,
`Bezeichnung` varchar(45) NOT NULL,
PRIMARY KEY (`ID`),
UNIQUE KEY `Bezeichnung_UNIQUE` (`Bezeichnung`),
KEY `ix_sprache_id` (`ID`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8
To add a foreign key (grade_id) to an existing table (users), follow the following steps:
ALTER TABLE users ADD grade_id SMALLINT UNSIGNED NOT NULL DEFAULT 0;
ALTER TABLE users ADD CONSTRAINT fk_grade_id FOREIGN KEY (grade_id) REFERENCES grades(id);
Simply use this query, I have tried it as per my scenario and it works well
ALTER TABLE katalog ADD FOREIGN KEY (`Sprache`) REFERENCES Sprache(`ID`);
Simple Steps...
ALTER TABLE t_name1 ADD FOREIGN KEY (column_name) REFERENCES t_name2(column_name)
FOREIGN KEY (`Sprache`)
REFERENCES `Sprache` (`ID`)
ON DELETE SET NULL
ON UPDATE SET NULL;
But your table has:
CREATE TABLE `katalog` (
`Sprache` int(11) NOT NULL,
It cant set the column Sprache to NULL because it is defined as NOT NULL.
check this link. It has helped me with errno 150:
http://verysimple.com/2006/10/22/mysql-error-number-1005-cant-create-table-mydbsql-328_45frm-errno-150/
On the top of my head two things come to mind.
Is your foreign key index a unique name in the whole database (#3 in the list)?
Are you trying to set the table PK to NULL on update (#5 in the list)?
I'm guessing the problem is with the set NULL on update (if my brains aren't on backwards today as they so often are...).
Edit: I missed the comments on your original post. Unsigned/not unsigned int columns maybe resolved your case. Hope my link helps someone in the future thought.
How to fix Error Code: 1005. Can't create table 'mytable.#sql-7fb1_7d3a' (errno: 150) in mysql.
alter your table and add an index to it..
ALTER TABLE users ADD INDEX index_name (index_column)
Now add the constraint
ALTER TABLE foreign_key_table
ADD CONSTRAINT foreign_key_name FOREIGN KEY (foreign_key_column)
REFERENCES primary_key_table (primary_key_column) ON DELETE NO ACTION
ON UPDATE CASCADE;
Note if you don't add an index it wont work.
After battling with it for about 6 hours I came up with the solution
I hope this save a soul.
MySQL will execute this query:
ALTER TABLE `db`.`table1`
ADD COLUMN `col_table2_fk` INT UNSIGNED NULL,
ADD INDEX `col_table2_fk_idx` (`col_table2_fk` ASC),
ADD CONSTRAINT `col_table2_fk1`
FOREIGN KEY (`col_table2_fk`)
REFERENCES `db`.`table2` (`table2_id`)
ON DELETE NO ACTION
ON UPDATE NO ACTION;
Cheers!
When you add a foreign key constraint to a table using ALTER TABLE, remember to create the required indexes first.
Create index
Alter table
try all in one query
ALTER TABLE users ADD grade_id SMALLINT UNSIGNED NOT NULL DEFAULT 0,
ADD CONSTRAINT fk_grade_id FOREIGN KEY (grade_id) REFERENCES grades(id);
step 1: run this script
SET FOREIGN_KEY_CHECKS=0;
step 2: add column
ALTER TABLE mileage_unit ADD COLUMN COMPANY_ID BIGINT(20) NOT NULL
step 3: add foreign key to the added column
ALTER TABLE mileage_unit
ADD FOREIGN KEY (COMPANY_ID) REFERENCES company_mst(COMPANY_ID);
step 4: run this script
SET FOREIGN_KEY_CHECKS=1;
ALTER TABLE child_table_name ADD FOREIGN KEY (child_table_column) REFERENCES parent_table_name(parent_table_column);
child_table_name is that table in which we want to add constraint.
child_table_column is that table column in which we want to add foreign key.
parent table is that table from which we want to take reference.
parent_table_column is column name of the parent table from which we take reference
this is basically happens because your tables are in two different charsets. as a example one table created in charset=utf-8 and other tables is created in CHARSET=latin1 so you want be able add foriegn key to these tables. use same charset in both tables then you will be able to add foriegn keys. error 1005 foriegn key constraint incorrectly formed can resolve from this
The foreign key constraint must be the same data type as the primary key in the reference table and column
ALTER TABLE TABLENAME ADD FOREIGN KEY (Column Name) REFERENCES TableName(column name)
Example:-
ALTER TABLE Department ADD FOREIGN KEY (EmployeeId) REFERENCES Employee(EmployeeId)
i geted through the same problem. I my case the table already have data and there were key in this table that was not present in the reference table. So i had to delete this rows that disrespect the constraints and everything worked.
Double check if the engine and charset of the both tables are the same.
If not, it will show this error.