Alter

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`