I'm new to SQL and trying to learn how to reference on table to another. This is what I have:
CREATE TABLE IF NOT EXISTS itemData (
id int(11) AUTO_INCREMENT PRIMARY KEY,
title varchar(64) NOT NULL,
sector_id int(11) DEFAULT NULL,
status_id int(11) DEFAULT NULL,
locations_id int(11) DEFAULT NULL,
payments_id int(11) DEFAULT NULL,
type_id int(11) DEFAULT NULL,
CONSTRAINT `fk_sector_id` FOREIGN KEY (sector_id) REFERENCES `sector` (`sector_id`),
CONSTRAINT `fk_status_id` FOREIGN KEY (`status_id`) REFERENCES `status` (`status_id`),
CONSTRAINT `fk_locations_id` FOREIGN KEY (`locations_id`) REFERENCES `location` (`locations_id`),
CONSTRAINT `fk_payments_id` FOREIGN KEY (`payments_id`) REFERENCES `payments` (`payments_id`),
CONSTRAINT `fk_type_id` FOREIGN KEY (`type_id`) REFERENCES `type` (`type_id`)
);
Then I have my reference table for example:
CREATE TABLE IF NOT EXISTS itemStatus (
id int(11) AUTO_INCREMENT PRIMARY KEY,
name varchar(64) NOT NULL UNIQUE KEY
);
This doesn't seem to validate, can someone tell me where I have gone wrong please?
You probably need to change your table definition like this:
CREATE TABLE IF NOT EXISTS itemStatus (
status_id int(11) AUTO_INCREMENT PRIMARY KEY,
name varchar(64) NOT NULL UNIQUE KEY
);
as the constraint definition in your table is like this:
CONSTRAINT `fk_status_id` FOREIGN KEY (`status_id`) REFERENCES `itemstatus` (`status_id`),
You need to update the correct table in the constraint.
Also if you dont want to change the table definition then change the constraint like this:
CONSTRAINT `fk_id` FOREIGN KEY (`id`) REFERENCES `itemstatus` (`id`)
Here's your constraint:
CONSTRAINT `fk_status_id` FOREIGN KEY (`status_id`) REFERENCES `status` (`status_id`)
Here's the table definition:
CREATE TABLE IF NOT EXISTS itemStatus (
id int(11) AUTO_INCREMENT PRIMARY KEY,
name varchar(64) NOT NULL UNIQUE KEY
);
There's no column named status_id in that table.
Either rename the primary key column to status_id or change the constraint to point to id.
Related
I am trying to create a child table that constraints 3 foreign keys from the parent but I receive an error 1215: cannot add foreign key constraint
parent table:
CREATE TABLE `Availability` (
`time_of_day` varchar(20) NOT NULL,
`day_of_week` varchar(20) NOT NULL,
`email` varchar(60) NOT NULL,
PRIMARY KEY (`time_of_day`,`day_of_week`,`email`),
KEY `email` (`email`),
CONSTRAINT `Availability_ibfk_1` FOREIGN KEY (`email`) REFERENCES `service_provider` (`email_service_provider`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8
child table (which I cant build due to error mentioned above):
CREATE TABLE TEST1
(
num_request INT NOT NULL,
time_of_day VARCHAR(20) NOT NULL,
day_of_week VARCHAR(20) NOT NULL,
email VARCHAR(60) NOT NULL,
PRIMARY KEY (num_request),
Foreign key (time_of_day) references Availability(time_of_day),
Foreign key (day_of_week) references Availability(day_of_week),
Foreign key (email) references Availability(email)
);
Please show me what I'm doing wrong... Thank you all.
When you're making a foreign key to a table with a composite primary key (i.e. a key of multiple columns), you should make the foreign key composite as well.
CREATE TABLE TEST1
(
num_request INT NOT NULL,
time_of_day VARCHAR(20) NOT NULL,
day_of_week VARCHAR(20) NOT NULL,
email VARCHAR(60) NOT NULL,
PRIMARY KEY (num_request),
Foreign key (time_of_day, day_of_week, email) references Availability(time_of_day, day_of_week, email)
)
The columns of the foreign key should match the columns of the primary or unique key they reference. They should have the same number of columns, in the same order.
What you tried to do was create three separate constraints of one column each.
this is the parent table
CREATE TABLE trax_zone(
trax_zone_id INT(11) NOT NULL AUTO_INCREMENT PRIMARY KEY,
trax_zone_name VARCHAR(255) NOT NULL,
)ENGINE=InnoDB;
this is the child table code
CREATE TABLE city(
city_id INT(11) NOT NULL AUTO_INCREMENT PRIMARY KEY,
city_name VARCHAR(255) NOT NULL,
FOREIGN KEY fk_trax(trax_zone_id) REFERENCES trax_zone(trax_zone_id) ON UPDATE CASCADE ON DELETE RESTRICT,
FOREIGN KEY fk_zoop(zoop_zone_id) REFERENCES zoop_zone(zoop_zone_id) ON UPDATE CASCADE ON DELETE RESTRICT
)ENGINE=InnoDB;
i am new to mysql , kindly guide me
I don't understand how to link two tables together. This is an example:
CREATE TABLE IF NOT EXISTS itemStatus (
id int(11) AUTO_INCREMENT PRIMARY KEY,
name varchar(64) NOT NULL UNIQUE KEY
);
CREATE TABLE IF NOT EXISTS itemData (
id int(11) AUTO_INCREMENT PRIMARY KEY,
title varchar(64) NOT NULL,
status_id int(11) DEFAULT NULL,
CONSTRAINT `fk_id` FOREIGN KEY (`id`) REFERENCES `itemStatus` (`id`),
);
I'm calling the row "status_id" but I don't reference this anywhere, so it can't link the two. For this example, should should my "CONSTRAINT" line read in order to be correct?
A FOREIGN KEY in one table points to a PRIMARY KEY in another table.
Take a look at:
http://www.w3schools.com/sql/sql_foreignkey.asp
So it should be:
CREATE TABLE IF NOT EXISTS itemStatus (
id int(11) AUTO_INCREMENT PRIMARY KEY,
name varchar(64) NOT NULL UNIQUE KEY
);
CREATE TABLE IF NOT EXISTS itemData (
id int(11) AUTO_INCREMENT PRIMARY KEY,
title varchar(64) NOT NULL,
status_id int(11) DEFAULT NULL,
CONSTRAINT `fk_id` FOREIGN KEY (`status_id`) REFERENCES `itemStatus` (`id`)
);
FOREIGN KEY (status_id) => Field in the table will REFERENCES itemStatus (id)
Constraint can't have "," when it's the last:
(...) REFERENCES itemStatus (id),
So the structure should be:
CONSTRAINT <<CONSTRAINT_NAME>> FOREIGN KEY (<<COLUMN_IN_THE_TABLE>>) REFERENCES `<<ANOTHER_TABLE>>` (`<<ANOTHER_TABLE_COLUMN_ID>>`)
Looks like you're very close. Try this instead:
CONSTRAINT `fk_id` FOREIGN KEY (`status_id`) REFERENCES `itemStatus` (`id`)
Your constraint is linking two primary keys (id of table 1 with id of table 2).
It should be something like this:
CREATE TABLE IF NOT EXISTS itemData (
id int(11) AUTO_INCREMENT PRIMARY KEY,
title varchar(64) NOT NULL,
status_id int(11) DEFAULT NULL,
CONSTRAINT `fk_id` FOREIGN KEY (`status_id`) REFERENCES `itemStatus` (`id`)
);
How can I make 3 columns have a field reference? The code below is incorrect.
CREATE TABLE `example` (
`id` bigint(20) NOT NULL AUTO_INCREMENT,
`userid_do1` int(11) DEFAULT NULL,
`userid_do2` int(11) DEFAULT NULL,
`userid_do3` int(11) DEFAULT NULL,
PRIMARY KEY (`id`),
CONSTRAINT `example_ibfk_1` FOREIGN KEY (`userid_do1,userid_do2,userid_do3`) REFERENCES `usertable` (`id`),
) ENGINE=InnoDB
you need to create one constraint for each column that references to another table's column.
CONSTRAINT example_ibfk_1 FOREIGN KEY (userid_do1) REFERENCES usertable(id),
CONSTRAINT example_ibfk_2 FOREIGN KEY (userid_do2) REFERENCES usertable(id),
CONSTRAINT example_ibfk_3 FOREIGN KEY (userid_do3) REFERENCES usertable(id)
CREATE TABLE IF NOT EXISTS `questions` (
`question_id` int(11) NOT NULL AUTO_INCREMENT,
`createddate` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
`updateddate` timestamp NULL DEFAULT NULL,
`active_flag` tinyint(4) NOT NULL DEFAULT '0',
PRIMARY KEY (`question_id`),
UNIQUE KEY `id_UNIQUE` (`question_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=1 ;
CREATE TABLE `alarts` (
`alart_id` BIGINT(20) unsigned NOT NULL AUTO_INCREMENT,
`alart_name` varchar(45) NOT NULL,
`interval` int(10) unsigned NOT NULL,
`alart_sent_counter` int(10) unsigned NOT NULL,
`alart_types_id` BIGINT(20) unsigned NOT NULL,
`contact_group_id` int(10) unsigned NOT NULL,
PRIMARY KEY (`alart_id`),
FOREIGN KEY (`alart_types_id`) REFERENCES alart_types(`alart_types_id`)
) ENGINE=InnoDB AUTO_INCREMENT=20 DEFAULT CHARSET=utf8;
I want to create new table with two FOREIGN KEY like this:
CREATE TABLE `alart_question_mapping` (
`alart_question_mapping_id` BIGINT(20) unsigned NOT NULL AUTO_INCREMENT,
`question_id` int(11) NOT NULL,
`alart_id` BIGINT(20) unsigned NOT NULL,
PRIMARY KEY (`alart_question_mapping_id`),
FOREIGN KEY (`question_id`) REFERENCES questions(`question_id`),
FOREIGN KEY (`alart_id`) REFERENCES alart_types(`alart_id`)
) ENGINE=InnoDB AUTO_INCREMENT=20 DEFAULT CHARSET=utf8;
but I am getting error:
Error Code: 1005. Can't create table 'alart_question_mapping' (errno: 150)
How can I create this table ?
Thank's.
Chane the statement:
FOREIGN KEY (`alart_id`) REFERENCES alart_types(`alart_id`)
to
FOREIGN KEY (`alart_id`) REFERENCES alarts(`alart_id`)
The only thing I can see is you are referencing a table in your CREATE TABLE statement that is not present in what you provided:
FOREIGN KEY (`alart_id`) REFERENCES alart_types(`alart_id`)
If you remove this reference the table will create. See SQL Fiddle with Demo
Edit #1, based on your update the problem is you are referencing the wrong field in your last table:
Change this:
CREATE TABLE `alart_question_mapping` (
`alart_question_mapping_id` BIGINT(20) unsigned NOT NULL AUTO_INCREMENT,
`question_id` int(11) NOT NULL,
`alart_id` BIGINT(20) unsigned NOT NULL,
PRIMARY KEY (`alart_question_mapping_id`),
FOREIGN KEY (`question_id`) REFERENCES questions(`question_id`),
FOREIGN KEY (`alart_id`) REFERENCES alart_types(`alart_id`)
)
To this:
CREATE TABLE `alart_question_mapping` (
`alart_question_mapping_id` BIGINT(20) unsigned NOT NULL AUTO_INCREMENT,
`question_id` int(11) NOT NULL,
`alart_id` BIGINT(20) unsigned NOT NULL,
PRIMARY KEY (`alart_question_mapping_id`),
FOREIGN KEY (`question_id`) REFERENCES questions(`question_id`),
FOREIGN KEY (`alart_id`) REFERENCES alart_types(`alart_types_id`)
) ENGINE=InnoDB AUTO_INCREMENT=20 DEFAULT CHARSET=utf8;
So you are changing this line:
FOREIGN KEY (`alart_id`) REFERENCES alart_types(`alart_id`)
to this:
FOREIGN KEY (`alart_id`) REFERENCES alart_types(`alart_types_id`)
If you are referencing the alart_types table then you will want to reference the alart_types_id not the alart_id
see SQL Fiddle with Demo
It can't find table alart_types.
From MySQL Foreign Key Constraints
If you re-create a table that was dropped, it must have a definition
that conforms to the foreign key constraints referencing it. It must
have the right column names and types, and it must have indexes on the
referenced keys, as stated earlier. If these are not satisfied, MySQL
returns error number 1005 and refers to error 150 in the error
message.
I think you mean
FOREIGN KEY (`alart_id`) REFERENCES alart(`alart_id`)
instead of
FOREIGN KEY (`alart_id`) REFERENCES alart_types(`alart_id`)
Hope this makes sense.
In this table
CREATE TABLE alart_types (
alart_types_id BIGINT(20) unsigned NOT NULL AUTO_INCREMENT,
alarts_types_name varchar(45) NOT NULL,
PRIMARY KEY (alart_types_id)
) ENGINE=InnoDB AUTO_INCREMENT=20 DEFAULT CHARSET=utf8;
it doesn't really make sense to have an autoincrement id number without also having a unique constraint on alarts_types_name. Without that unique constraint, you're almost certain to end up with a table whose data looks like this.
1 Warning
2 Critical
3 Warning
4 Warning
This constraint references a column that doesn't exist.
FOREIGN KEY (`alart_id`) REFERENCES alart_types(`alart_id`)
It should be
FOREIGN KEY (`alart_id`) REFERENCES alart_types(`alart_types_id`)