Creating Table Constraints

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Sometimes you want to add constraints on a table level, rather than a column level. The following methods will let you accomplish that.

foreignKey

Create a foreign key constraint from one or more columns. Follow up this call with calls to the TableIndex's references and onTable methods.

Argument

Type

Required

Default

Description

columns

string or array

true

The column or array of columns that references a key or keys on another table.

name

string

false

A generated name consisting of the table name and column name(s).

The name of the foreign key constraint.

Example:

SchemaBuilder

schema.create( "users", function( table ) {
table.unsignedInteger( "country_id" );
table.foreignKey( "country_id" ).references( "id" ).onTable( "countries" );
} );

SQL (MySQL)

CREATE TABLE `users` (
`country_id` INTEGER UNSIGNED NOT NULL,
CONSTRAINT `fk_users_country_id` FOREIGN KEY (`country_id`) REFERENCES `countries` (`id`) ON UPDATE NO ACTION ON DELETE NO ACTION
)

index

Create a generic index from one or more columns.

Argument

Type

Required

Default

Description

columns

string or array

true

The column or array of columns that make up the index.

name

string

false

A generated name consisting of the table name and column name(s).

The name of the index constraint.

Example:

SchemaBuilder

schema.create( "users", function( table ) {
table.string( "first_name" );
table.string( "last_name" );
table.index( [ "first_name", "last_name" ], "idx_users_full_name" );
} );

SQL (MySQL)

CREATE TABLE `users` (
`first_name` VARCHAR(255) NOT NULL,
`last_name` VARCHAR(255) NOT NULL,
INDEX `idx_users_full_name` (`first_name`, `last_name`)
)

primaryKey

Create a primary key constraint from one or more columns.

Argument

Type

Required

Default

Description

columns

string or array

true

The column or array of columns that make up the primary key.

name

string

false

A generated name consisting of the table name and column name(s).

The name of the primary key constraint.

Example:

SchemaBuilder

schema.create( "posts_users", function( table ) {
table.unsignedInteger( "post_id" ).references( "id" ).onTable( "posts" );
table.unsignedInteger( "user_id" ).references( "id" ).onTable( "users" );
table.primaryKey( [ "post_id", "user_id" ], "pk_posts_users" );
} );

SQL (MySQL)

CREATE TABLE `posts_users` (
`post_id` VARCHAR(255) NOT NULL,
`user_id` VARCHAR(255) NOT NULL,
INDEX `idx_users_full_name` (`first_name`, `last_name`),
CONSTRAINT `fk_posts_users_post_id` FOREIGN KEY (`post_id`) REFERENCES `posts` (`id`) ON UPDATE NO ACTION ON DELETE NO ACTION,
CONSTRAINT `fk_posts_users_user_id` FOREIGN KEY (`user_id`) REFERENCES `users` (`id`) ON UPDATE NO ACTION ON DELETE NO ACTION,
CONSTRAINT ""pk_users_first_name_last_name"" PRIMARY KEY (""first_name"", ""last_name"")
)

unique

Create a unique constraint from one or more columns.

Argument

Type

Required

Default

Description

columns

string or array

true

The column or array of columns that make up the unique constraint.

name

string

false

A generated name consisting of the table name and column name(s).

The name of the unique constraint.

Example:

SchemaBuilder

schema.create( "users", function( table ) {
table.increments( "id" );
table.string( "username ");
table.unique( "username" );
} );

SQL (MySQL)

CREATE TABLE `users` (
`id` INTEGER UNSIGNED NOT NULL AUTO_INCREMENT,
UNIQUE (`username`)
)