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class Cql::AlterTable

Reference < Object

This module is part of the Cql namespace and is responsible for handling database alterations. This class represents an AlterTable object.

Example :

alter_table = AlterTable.new
alter_table.add_column(:email, "string")
alter_table.drop_column(:age)
alter_table.rename_column(:email, :user_email)
alter_table.change_column(:age, "string")

=> #<AlterTable:0x00007f8e7a4e1e80>

Constructors

def new(table : Cql::Table, schema : Cql::Schema)

Instance Methods

def add_column(name : Symbol, type : Any, as as_name : String | Nil = nil, null : Bool = true, default : DB::Any = nil, unique : Bool = false, size : Int32 | Nil = nil, index : Bool = false)

Adds a new column to the table.

  • @param name [Symbol] the name of the column to be added

  • @param type [Any] the data type of the column

  • @param as_name [String, nil] an optional alias for the column

  • @param null [Bool] whether the column allows null values (default: true)

  • @param default [DB::Any, nil] the default value for the column (default: nil)

  • @param unique [Bool] whether the column should have a unique constraint (default: false)

  • @param size [Int32, nil] the size of the column (default: nil)

  • @param index [Bool] whether the column should be indexed (default: false)

Example Adding a new column with default options

add_column(:email, "string")

Example Adding a new column with custom options

add_column(:age, "integer", null: false, default: "18")

def change_column(name : Symbol, type : Any)

Changes the type of a column in the table.

  • @param name [Symbol] the name of the column to be changed

  • @param type [Any] the new data type for the column

Example Changing the type of a column

change_column(:age, "string")

def create_index(name : Symbol, columns : Array(Symbol), unique : Bool = false)

Creates an index on the table.

  • @param name [Symbol] the name of the index

  • @param columns [Array(Symbol)] the columns to be indexed

  • @param unique [Bool] whether the index should be unique (default: false)

Example Creating an index

create_index(:index_users_on_email, [:email], unique: true)

def drop_column(column : Symbol)

Drops a column from the table.

  • @param column [Symbol] the name of the column to be dropped

Example Dropping a column

drop_column(:age)

def drop_foreign_key(name : Symbol)

Drops a foreign key from the table.

  • @param name [Symbol] the name of the foreign key to be dropped

Example Dropping a foreign key

drop_foreign_key(:fk_user_id)

def drop_index(name : Symbol)

Drops an index from the table.

  • @param name [Symbol] the name of the index to be dropped

Example Dropping an index

drop_index(:index_users_on_email)

def foreign_key(name : Symbol, columns : Array(Symbol), table : Symbol, references : Array(Symbol), on_delete : String = "NO ACTION", on_update : String = "NO ACTION")

Adds a foreign key to the table.

  • @param name [Symbol] the name of the foreign key

  • @param columns [Array(Symbol)] the columns in the current table

  • @param table [Symbol] the referenced table

  • @param references [Array(Symbol)] the columns in the referenced table

  • @param on_delete [String] the action on delete (default: "NO ACTION")

  • @param on_update [String] the action on update (default: "NO ACTION")

Example Adding a foreign key

foreign_key(:fk_user_id, [:user_id], :users, [:id], on_delete: "CASCADE")

def rename_column(old_name : Symbol, new_name : Symbol)

Renames a column in the table.

  • @param old_name [Symbol] the current name of the column

  • @param new_name [Symbol] the new name for the column

Example Renaming a column

  rename_column(:email, :user_email)

def rename_table(new_name : Symbol)

Renames the table.

  • @param new_name [Symbol] the new name for the table

Example Renaming the table

rename_table(:new_table_name)

def to_sql(visitor : Expression::Visitor)

Converts the alter table actions to SQL.

  • @param visitor [Expression::Visitor] the visitor to generate SQL

  • @return [String] the generated SQL

Example Generating SQL for alter table actions

sql = to_sql(visitor)
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