- Inheritance
Methods
Instance
Visibility | Signature |
---|---|
public | add_column (table_name, column_name, type, options = {}) |
public | add_index (table_name, column_name, options = {}) |
public | add_order_by_for_association_limiting! (sql, options) |
public | add_timestamps (table_name) |
public | assume_migrated_upto_version (version) |
public | change_column (table_name, column_name, type, options = {}) |
public | change_column_default (table_name, column_name, default) |
public | change_table (table_name) {|Table.new(table_name, self)| ...} |
public | columns (table_name, name = nil) |
public | create_table (table_name, options = {}) {|table_definition| ...} |
public | distinct (columns, order_by) |
public | drop_table (table_name, options = {}) |
public | initialize_schema_migrations_table () |
public | native_database_types () |
public | remove_column (table_name, *column_names) |
public | remove_columns (table_name, *column_names) |
public | remove_index (table_name, options = {}) |
public | remove_timestamps (table_name) |
public | rename_column (table_name, column_name, new_column_name) |
public | rename_table (table_name, new_name) |
public | structure_dump () |
public | table_alias_for (table_name) |
public | table_alias_length () |
public | table_exists? (table_name) |
protected | options_include_default? (options) |
Instance Method Detail
add_column(table_name, column_name, type, options = {})
Adds a new column to the named table. See TableDefinition#column for details of the options you can use.
add_index(table_name, column_name, options = {})
Adds a new index to the table. column_name can be a single Symbol, or an Array of Symbols.
The index will be named after the table and the first column name, unless you pass :name as an option.
When creating an index on multiple columns, the first column is used as a name for the index. For example, when you specify an index on two columns [:first, :last], the DBMS creates an index for both columns as well as an index for the first column :first. Using just the first name for this index makes sense, because you will never have to create a singular index with this name.
Examples
Creating a simple index
add_index(:suppliers, :name)
generates
CREATE INDEX suppliers_name_index ON suppliers(name)
Creating a unique index
add_index(:accounts, [:branch_id, :party_id], :unique => true)
generates
CREATE UNIQUE INDEX accounts_branch_id_party_id_index ON accounts(branch_id, party_id)
Creating a named index
add_index(:accounts, [:branch_id, :party_id], :unique => true, :name => 'by_branch_party')
generates
CREATE UNIQUE INDEX by_branch_party ON accounts(branch_id, party_id)
add_order_by_for_association_limiting!(sql, options)
ORDER BY clause for the passed order option. PostgreSQL overrides this due to its stricter standards compliance.
add_timestamps(table_name)
Adds timestamps (created_at and updated_at) columns to the named table.
Examples
add_timestamps(:suppliers)
assume_migrated_upto_version(version)
change_column(table_name, column_name, type, options = {})
Changes the column‘s definition according to the new options. See TableDefinition#column for details of the options you can use.
Examples
change_column(:suppliers, :name, :string, :limit => 80) change_column(:accounts, :description, :text)
change_column_default(table_name, column_name, default)
Sets a new default value for a column. If you want to set the default value to NULL, you are out of luck. You need to DatabaseStatements#execute the appropriate SQL statement yourself.
Examples
change_column_default(:suppliers, :qualification, 'new') change_column_default(:accounts, :authorized, 1)
change_table(table_name) {|Table.new(table_name, self)| ...}
A block for changing columns in table.
Example
# change_table() yields a Table instance change_table(:suppliers) do |t| t.column :name, :string, :limit => 60 # Other column alterations here end
Examples
Add a column
change_table(:suppliers) do |t| t.column :name, :string, :limit => 60 end
Add 2 integer columns
change_table(:suppliers) do |t| t.integer :width, :height, :null => false, :default => 0 end
Add created_at/updated_at columns
change_table(:suppliers) do |t| t.timestamps end
Add a foreign key column
change_table(:suppliers) do |t| t.references :company end
Creates a company_id(integer) column
Add a polymorphic foreign key column
change_table(:suppliers) do |t| t.belongs_to :company, :polymorphic => true end
Creates company_type(varchar) and company_id(integer) columns
Remove a column
change_table(:suppliers) do |t| t.remove :company end
Remove several columns
change_table(:suppliers) do |t| t.remove :company_id t.remove :width, :height end
Remove an index
change_table(:suppliers) do |t| t.remove_index :company_id end
See also Table for details on all of the various column transformation
columns(table_name, name = nil)
Returns an array of Column objects for the table specified by table_name. See the concrete implementation for details on the expected parameter values.
create_table(table_name, options = {}) {|table_definition| ...}
Creates a new table with the name table_name. table_name may either be a String or a Symbol.
There are two ways to work with create_table. You can use the block form or the regular form, like this:
Block form
# create_table() passes a TableDefinition object to the block. # This form will not only create the table, but also columns for the # table. create_table(:suppliers) do |t| t.column :name, :string, :limit => 60 # Other fields here end
Regular form
# Creates a table called 'suppliers' with no columns. create_table(:suppliers) # Add a column to 'suppliers'. add_column(:suppliers, :name, :string, {:limit => 60})
The options hash can include the following keys:
- :id
- Whether to automatically add a primary key column. Defaults to true. Join tables for has_and_belongs_to_many should set :id => false.
- :primary_key
- The name of the primary key, if one is to be added automatically. Defaults to id.
- :options
- Any extra options you want appended to the table definition.
- :temporary
- Make a temporary table.
- :force
- Set to true to drop the table before creating it. Defaults to false.
Examples
Add a backend specific option to the generated SQL (MySQL)
create_table(:suppliers, :options => 'ENGINE=InnoDB DEFAULT CHARSET=utf8')
generates:
CREATE TABLE suppliers ( id int(11) DEFAULT NULL auto_increment PRIMARY KEY ) ENGINE=InnoDB DEFAULT CHARSET=utf8
Rename the primary key column
create_table(:objects, :primary_key => 'guid') do |t| t.column :name, :string, :limit => 80 end
generates:
CREATE TABLE objects ( guid int(11) DEFAULT NULL auto_increment PRIMARY KEY, name varchar(80) )
Do not add a primary key column
create_table(:categories_suppliers, :id => false) do |t| t.column :category_id, :integer t.column :supplier_id, :integer end
generates:
CREATE TABLE categories_suppliers ( category_id int, supplier_id int )
See also TableDefinition#column for details on how to create columns.
distinct(columns, order_by)
SELECT DISTINCT clause for a given set of columns and a given ORDER BY clause. Both PostgreSQL and Oracle overrides this for custom DISTINCT syntax.
distinct("posts.id", "posts.created_at desc")
drop_table(table_name, options = {})
Drops a table from the database.
initialize_schema_migrations_table()
Should not be called normally, but this operation is non-destructive. The migrations module handles this automatically.
native_database_types()
Returns a Hash of mappings from the abstract data types to the native database types. See TableDefinition#column for details on the recognized abstract data types.
remove_column(table_name, *column_names)
Removes the column(s) from the table definition.
Examples
remove_column(:suppliers, :qualification) remove_columns(:suppliers, :qualification, :experience)
remove_columns(table_name, *column_names)
Alias for remove_column
remove_index(table_name, options = {})
Remove the given index from the table.
Remove the suppliers_name_index in the suppliers table.
remove_index :suppliers, :name
Remove the index named accounts_branch_id_index in the accounts table.
remove_index :accounts, :column => :branch_id
Remove the index named accounts_branch_id_party_id_index in the accounts table.
remove_index :accounts, :column => [:branch_id, :party_id]
Remove the index named by_branch_party in the accounts table.
remove_index :accounts, :name => :by_branch_party
remove_timestamps(table_name)
Removes the timestamp columns (created_at and updated_at) from the table definition.
Examples
remove_timestamps(:suppliers)
rename_column(table_name, column_name, new_column_name)
Renames a column.
Example
rename_column(:suppliers, :description, :name)
rename_table(table_name, new_name)
Renames a table.
Example
rename_table('octopuses', 'octopi')
structure_dump()
Returns a string of CREATE TABLE SQL statement(s) for recreating the entire structure of the database.
table_alias_for(table_name)
Truncates a table alias according to the limits of the current adapter.
table_alias_length()
This is the maximum length a table alias can be
table_exists?(table_name)
def tables(name = nil) end