Alter

Last updated 8 months ago

The alter method loads up an existing table in order to make modifications. These modifications may include adding, renaming, or dropping columns and constraints.

To begin altering an existing table, call the alter method off of the SchemaBuilder. This method takes a callback as the second parameter that is passed a Blueprint object, much like the create method.

Argument

Type

Required

Default

Description

table

string

true

The name of the table to alter.

callback

function

true

A callback function used to define the alterations to the table. It is passed a Blueprint as the only argument.

options

struct

false

{}

Options to pass to queryExecute.

execute

boolean

false

true

Run the query immediately after building it.

Calling multiple methods inside a single alter callback creates multiple SQL statements to be executed. qb takes care of this execution for you by default.

The following methods off of Blueprint let you modify the table inside the callback:

addColumn

Add a new column to an existing table. Takes a Column instance as the only argument.

Any instance of Column is valid like those returned by the column methods (integer, string, etc.) as well as the column modifier methods (unsigned, nullable, etc.).

Argument

Type

Required

Default

Description

column

Column

true

A column object to add to the table.

Example:

SchemaBuilder

schema.alter( "users", function( table ) {
table.addColumn( table.boolean( "is_active" ) );
} );

SQL (MySQL)

ALTER TABLE `users` ADD `is_active` TINYINT(1) NOT NULL

dropColumn

Drop a column on an existing table.

Argument

Type

Required

Default

Description

name

string

true

The name of the column to drop.

Example:

SchemaBuilder

schema.alter( "users", function( table ) {
table.dropColumn( "username" );
} );

SQL (MySQL)

ALTER TABLE `users` DROP COLUMN `username`

modifyColumn

Modify an existing column on a table.

Argument

Type

Required

Default

Description

name

string

true

The name of the column to modify.

column

Column

true

A column object to replace the named column.

Example:

SchemaBuilder

schema.alter( "users", function( table ) {
table.modifyColumn( "name", table.string( "username" ) );
} );

SQL (MySQL)

ALTER TABLE `users` CHANGE `name` `username` VARCHAR(255) NOT NULL

renameColumn

Rename a column on a table. A full Column instance is required as the second argument for Grammars that need to redeclare the column definition when renaming.

Argument

Type

Required

Default

Description

name

string

true

The current name of a column.

column

Column

true

A column object with the new column name and definition.

Example:

SchemaBuilder

schema.alter( "users", function( table ) {
table.renameColumn( "name", table.string( "username" ) );
} );

SQL (MySQL)

ALTER TABLE `users` CHANGE `name` `username` VARCHAR(255) NOT NULL

addConstraint

Add an index or key to an existing table. Any TableIndex instance is valid, like those created by the index methods (unique, index, primaryKey, etc.).

Argument

Type

Required

Default

Description

constraint

TableIndex

true

The TableIndex instance to add to the table.

Example:

SchemaBuilder

schema.alter( "users", function( table ) {
table.addConstraint( table.unique( "username" ) );
} );

SQL (MySQL)

ALTER TABLE `users` ADD CONSTRAINT `unq_users_username` UNIQUE (`username`)

dropConstraint

Drop an existing table constraint.

Argument

Type

Required

Default

Description

name

string OR TableIndex

true

The name of the constraint to drop. You can alternatively pass a TableIndex instance to use the dynamic name generated.

Example:

SchemaBuilder

schema.alter( "users", function( table ) {
table.dropConstraint( "unq_users_full_name" );
table.dropConstraint( table.unique( "username" ) );
} );

SQL (MySQL)

ALTER TABLE `users` DROP INDEX `unq_users_full_name`
ALTER TABLE `users` DROP INDEX `unq_users_username`

renameConstraint

Rename an existing table constraint.

Argument

Type

Required

Default

Description

oldName

string OR TableIndex

true

The old or current name of the constraint to rename. You can alternatively pass a TableIndex instance to use the dynamic name generated.

newName

string OR TableIndex

true

The new name of the constraint. You can alternatively pass a TableIndex instance to use the dynamic name generated.

Example:

SchemaBuilder

schema.alter( "users", function( table ) {
table.renameConstraint( "unq_users_first_name_last_name", "unq_users_full_name" );
} );

SQL (MySQL)

ALTER TABLE `users` RENAME INDEX `unq_users_first_name_last_name` TO `unq_users_full_name`