I need to change order of rows in database table.
My table has 4 columns and 7 rows. I need to reorder these rows
pk_i_id int(10) unsigned Auto Increment
s_name varchar(255) NULL
s_heading varchar(255) NULL
s_order_type varchar(10) NULL
In Adminer, when I've changed pk_i_id value(number) something else, I'm getting this error...
Cannot delete or update a parent row: a foreign key constraint fails (`database_name`.`oc_t_item_custom_attr_categories`, CONSTRAINT `oc_t_item_custom_attr_categories_ibfk_1` FOREIGN KEY (`fk_i_group_id`) REFERENCES `oc_t_item_custom_attr_groups` (`pk_i_id`))
Do you know how to change it ? Thank you
Edit
oc_t_item_custom_attr_categories
fk_i_group_id int(10) unsigned
fk_i_category_id int(10) unsigned
indexes
PRIMARY fk_i_group_id, fk_i_category_id
INDEX fk_i_category_id
foregin keys
fk_i_group_id oc_t_item_custom_attr_groups_2(pk_i_id) RESTRICT RESTRICT
fk_i_category_id oc_t_category(pk_i_id) RESTRICT RESTRICT
You need to change your foreign key on table database_name.oc_t_item_custom_attr_categories so that it updates along with column it references.
ALTER TABLE database_name.oc_t_item_custom_attr_categories DROP CONSTRAINT oc_t_item_custom_attr_categories_ibfk_1;
ALTER TABLE database_name.oc_t_item_custom_attr_categories
ADD CONSTRAINT oc_t_item_custom_attr_categories_ibfk_1 FOREIGN KEY (fk_i_group_id)
REFERENCES oc_t_item_custom_attr_groups (pk_i_id)
ON UPDATE CASCADE;
Since MariaDB seem to not support ADDING foreign keys after table creation, this is how it should work for you, assuming description of tables is correct:
RENAME TABLE oc_t_item_custom_attr_categories TO oc_t_item_custom_attr_categories_2;
CREATE TABLE oc_t_item_custom_attr_categories (
fk_i_group_id int(10) unsigned,
fk_i_category_id int(10) unsigned,
PRIMARY KEY(fk_i_group_id, fk_i_category_id),
INDEX (fk_i_category_id),
CONSTRAINT `oc_t_item_custom_attr_categories_ibfk_1` FOREIGN KEY (fk_i_group_id)
REFERENCES oc_t_item_custom_attr_groups (pk_i_id)
ON UPDATE CASCADE,
CONSTRAINT `oc_t_item_custom_attr_categories_ibfk_2` FOREIGN KEY (fk_i_category_id)
REFERENCES oc_t_category (pk_i_id)
) ENGINE = XtraDB; --change engine to what you are using
INSERT INTO oc_t_item_custom_attr_categories SELECT * FROM oc_t_item_custom_attr_categories_2;
How it works on example data in MySQL database: http://rextester.com/ZAKR50399
Related
I have a child table. and foreign key there with ON DELETE CASCADE while creating the table.
There are no records either in child or parent table.
I want the primary key, foreign key to be as they are but want to remove only the CASCADING option from the child table .
is there anyway that i can Alter that child table.
Thank you.
The table:
SHOW CREATE TABLE table;
CREATE TABLE `table` (
`id` int(11) unsigned NOT NULL AUTO_INCREMENT,
`id_departamento` int(11) unsigned DEFAULT NULL,
`name` varchar(30) COLLATE utf8mb4_unicode_ci NOT NULL,
PRIMARY KEY (`id`),
KEY `id_departamento` (`id_departamento`),
CONSTRAINT `departamentos_direcciones_pedidos_ibfk_1` FOREIGN KEY (`id_departamento`) REFERENCES `departamentos` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci
First drop foreign key.
ALTER TABLE departamentos_direcciones_pedidos DROP CONSTRAINT departamentos_direcciones_pedidos_ibfk_1;
Second, create the correct foreign key
ALTER TABLE departamentos_direcciones_pedidos ADD FOREIGN KEY (id_departamento) REFERENCES departamentos(id);
ON DELETE { NO ACTION | CASCADE | SET NULL | SET DEFAULT }
The default is NO ACTION.
So try altering your child table back to default.
(Oracle) You can only alter the state of a constraint. ON DELETE is not a state. So you need to drop constraint and recreate it.
drop table t1 cascade constraints;
create table t1 (id number unique, rid number constraint t1_fk references t1(id) on delete cascade);
alter table t1 drop constraint t1_fk;
alter table t1 add constraint t1_fk foreign key(rid) references t1(id);
if you're using Oracle there are different dictionary views which might help you to recreate the constraint correctly
Export the database as a .sql file
Then press ctrl + H to replace all ON DELETE CASCADE with ""
Then drop the tables from the DB and use the new file to instantiate a new one without ON DELETE CASCADE
I have the following T-SQL to create 3 SQL tables:
create table dbo.Posts
(
Id int identity not null
constraint PK_Posts_Id primary key clustered (Id),
Active bit not null
constraint DF_Posts_Active default (0)
);
create table dbo.PostsLocalized
(
Id int not null,
Culture int not null
constraint CK_PostsLocalized_Culture check ([Culture] in ('1', '2', '3')),
[Text] nvarchar (200) not null,
constraint PK_PostsLocalized_Id_Culture primary key clustered (Id, Culture)
);
create table dbo.Tags
(
Id int identity not null
constraint PK_Tags_Id primary key clustered (Id),
Name nvarchar not null
);
create table dbo.PostsLocalized_Tags
(
PostLocalizedId int not null,
TagId int not null,
constraint PK_PostsLocalized_Tags_Post_PostLocalizedId_TagId primary key clustered (PostLocalizedId, TagId)
);
Then I have added the following constraints:
alter table dbo.PostsLocalized
add constraint FK_PostsLocalized_Id foreign key (Id) references dbo.Posts(Id) on delete cascade on update cascade;
alter table dbo.PostsLocalized_Tags
add constraint FK_PostsLocalized_Tags_PostLocalizedId foreign key (PostLocalizedId) references PostsLocalized(Id) on delete cascade on update cascade,
constraint FK_PostsLocalized_Tags_TagId foreign key (TagId) references Tags(Id) on delete cascade on update cascade;
But I get the following error:
There are no primary or candidate keys in the referenced table 'PostsLocalized' that match the referencing column list in the foreign key 'FK_PostsLocalized_Tags_PostLocalizedId'.
How can I solve this?
Thank You,
Miguel
SQL Server mandates that foreign key references be to a primary key or unique key. The foreign key reference has to be to all the columns that constitute the primary/unique key. The documentation says:
In a foreign key reference, a link is created between two tables when
the column or columns that hold the primary key value for one table
are referenced by the column or columns in another table. This column
becomes a foreign key in the second table.
A FOREIGN KEY constraint does not have to be linked only to a PRIMARY
KEY constraint in another table; it can also be defined to reference
the columns of a UNIQUE constraint in another table. A FOREIGN KEY
constraint can contain null values; however, if any column of a
composite FOREIGN KEY constraint contains null values, verification of
all values that make up the FOREIGN KEY constraint is skipped. To make
sure that all values of a composite FOREIGN KEY constraint are
verified, specify NOT NULL on all the participating columns.
The primary key in PostsLocalized contains the culture column, so you need to add it into the foreign key reference.
Your PK on PostsLocalized table is complex consisting of two columns - id and culture and you are trying to create FK on only one of those columns which is not possible.
You'll have to either add Culture column on PostsLocalized_Tags and use them both in foreign key or remove Culture from your PK on PostLocalized
Is it possible to have a table's foreign key be part of another table's composite primary key?
For example, if I have two tables, one contains information on all active projects of different users and another containing information on what equipment is being used by the projects:
Project Table:
Composite Primary Keys: UserId, ProjectId (neither are unique by themselves)
Equipment Table:
Composite Primary Keys: UserId, ProjectId, EquipmentId (neither are unique by themselves)
Now is it possible to set the ProjectId in the equipment table to be a foreign key from the project table? When I try, I get an error saying that the column in Project Table do not match an existing primary key or unique constraint?
No.
When you create a foreign key, the key that you "point to" in the other table must be a UNIQUE or PRIMARY KEY constraint. You cannot establish a foreign key that points to a column that allow duplicate values. It would be very hard to imagine how the data should "act" if you update one of the duplicate values in the other table (for instance).
To do what you want you must establish a Projects table in which ProjectID is UNIQUE or a PRIMARY KEY and then point foreign keys in both the other tables to that table.
Parenthetically, you use the term "Primary Keys" to describe the columns in each table that make up the primary key. In fact, each table can have one and only one primary key. That key can be composed of one or more columns, but the key itself is still referred to in the singular. This is an important difference when using the primary key to optimize searches.
It do not know if that's a good design practice but for sure it is possible to have a composite foreign key of one table that is the part of the composite primary key of other table.
Say we have a table test1 having a composite primary key (A, B)
Now we can have a table say test2 having primary key (P, Q, R) where in (P,Q) of test2 referencing (A,B) of test2.
I ran the following script in the MySql database and it works just fine.
CREATE TABLE `test1` (
`A` INT NOT NULL,
`B` VARCHAR(2) NOT NULL,
`C` DATETIME NULL,
`D` VARCHAR(45) NULL,
PRIMARY KEY (`A`, `B`));
CREATE TABLE `test2` (
`P` INT NOT NULL,
`Q` VARCHAR(2) NOT NULL,
`R` INT NOT NULL,
`S` DATETIME NULL,
`T` VARCHAR(8) NULL,
PRIMARY KEY (`P`, `Q`, `R`),
INDEX `PQ_idx` (`P`,`Q` ASC),
CONSTRAINT `PQ`
FOREIGN KEY (`P`, `Q`)
REFERENCES `test1` (`A`,`B`)
ON DELETE CASCADE
ON UPDATE CASCADE);
In the above mentioned case, the database is expecting the combination of (A,B) to be unique and it is, being a primary key in test1 table.
But if you try to do something like following, the script would fail. The database would not let you create the test2 table.
CREATE TABLE `test2` (
`P` INT NOT NULL,
`Q` VARCHAR(2) NULL,
`R` DATETIME NULL,
`S` VARCHAR(8) NULL,
`T` VARCHAR(45) NULL,
INDEX `P_idx` (`P` ASC),
INDEX `Q_idx` (`Q` ASC),
CONSTRAINT `P`
FOREIGN KEY (`P`)
REFERENCES `test1` (`A`)
ON DELETE CASCADE
ON UPDATE CASCADE,
CONSTRAINT `Q`
FOREIGN KEY (`Q`)
REFERENCES `test1` (`B`)
ON DELETE CASCADE
ON UPDATE CASCADE);
In the above mentioned case database would expect the column A to be unique individually and the same follows for column B. It does not matter if combination of (A,B) is unique.
#Larry Lustig
The foreign key can be part of primary key in the other table.
source: Dependent relationship
Check relationship between tables: Zdarzenie(Event) and TypZdarzenia (type of event)
I created a foreign key in my sql by the following statemnt..
ALTER TABLE `users` ADD FOREIGN KEY ( `id`)
REFERENCES `user_login` (`user_id`)
ON DELETE CASCADE ;
The creation appears to succeed then after that I execute a delete statement
DELETE From user_login WHERE user_id = 1576;
yet in users the row still exists that is referencing that. I open up the mysql workbench and it doesn't show any signs that the foreign key was created. Does anyone know why this would be? Or what I am doing wrong? It is a one-to-one relationship in the two tables.
The table may be in MyISAM format, which does not support foreign keys.
Try converting it to InnoDB first:
alter table users engine=InnoDB;
You have to also make sure that both users.id and user_login.user_id have an index each.
Copy and paste this code in your Mysql script editor and run. You will have two tables categories and products these tables having cat_id as foreign key.
CREATE DATABASE IF NOT EXISTS dbdemo;
USE dbdemo;
CREATE TABLE categories(
cat_id int not null auto_increment primary key,
cat_name varchar(255) not null,
cat_description text
) ENGINE=InnoDB;
CREATE TABLE products(
prd_id int not null auto_increment primary key,
prd_name varchar(355) not null,
prd_price decimal,
cat_id int not null,
FOREIGN KEY fk_cat(cat_id)
REFERENCES categories(cat_id)
ON UPDATE CASCADE
ON DELETE RESTRICT
)ENGINE=InnoDB;
I'm not sure why these have to be unique, but from reading the MySQL forums it appears that they do. However, I think it has something more to do with the INDEX name. I have two tables that have foreign key constraints referencing the same primary key on a third table. If it helps, I'm using MySQL workbench to design the schema.
I usually name my foreign key on each table the same name as the primary key it references. I guess this isn't possible. It will create the first table with the foreign key constraint, but when it tries to create the second table it throws an error. Here is the second table it throws the error on:
CREATE TABLE IF NOT EXISTS `joe`.`products_to_categories` (
`product_to_category_id` INT NOT NULL AUTO_INCREMENT ,
`category_id` INT NOT NULL ,
`product_id` INT NOT NULL ,
PRIMARY KEY (`product_to_category_id`) ,
INDEX `category_id` (`category_id` ASC) ,
INDEX `product_id` (`product_id` ASC) ,
CONSTRAINT `category_id`
FOREIGN KEY (`category_id` )
REFERENCES `joe`.`categories` (`category_id` )
ON DELETE CASCADE
ON UPDATE NO ACTION,
CONSTRAINT `product_id`
FOREIGN KEY (`product_id` )
REFERENCES `joe`.`products` (`product_id` )
ON DELETE CASCADE
ON UPDATE NO ACTION)
ENGINE = InnoDB;
I want the foreign key names to be the same as the primary key in both of the other tables. What should I remove here so that I can use these names. What is the best practice here.
It is not possible because you would have a conflict in the filename for the file that is used for the index IIRC. I probably would name the key < tablename >_< column_name > or something like that.
You are creating an index (constraint) by the name of product_id via:
INDEX product_id
Then you are going and creating another constraint (for the foreign key) with the same name:
CONSTRAINT product_id
What you need to do is allow the server to provide a default, unique constraint name by removing the
CONSTRAINT product_id
See this URL: http://dev.mysql.com/doc/refman/5.1/en/innodb-foreign-key-constraints.html
"If the CONSTRAINT symbol clause is given, the symbol value must be unique in the database. If the clause is not given, InnoDB creates the name automatically."
In PostgreSQL, the default for naming indexes is to append "_pkey" and "_fkey" to the name of the primary and foreign key, respectively. So your case would look like:
INDEX `product_id_fkey` (`product_id` ASC) ,
UPDATE: I just tried this and it worked. See if that's what you had in mind.
use test;
create table if not exists test.product
(
product_id int not null auto_increment,
name varchar(80) not null,
primary key(product_id)
);
create table if not exists test.category
(
category_id int not null auto_increment,
name varchar(80) not null,
primary key(category_id)
);
create table if not exists test.product_category
(
product_id int,
category_id int,
primary key(product_id, category_id),
constraint product_id_fkey
foreign key(product_id) references product(product_id)
on delete cascade
on update no action,
constraint category_id_fkey
foreign key(category_id) references category(category_id)
on delete cascade
on update no action
);
insert into test.product(name) values('teddy bear');
insert into test.category(name) values('toy');
insert into test.product_category
select p.product_id, c.category_id from product as p, category as c
where p.name = 'teddy bear' and c.name = 'toy';