- add_column
- add_index
- change_column
- change_column_default
- columns
- create_table
- drop_table
- initialize_schema_information
- native_database_types
- remove_column
- remove_index
- rename_column
- rename_table
- structure_dump
- table_alias_for
- table_alias_length
Adds a new column to the named table. See TableDefinition#column for details of the options you can use.
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# File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 121 121: def add_column(table_name, column_name, type, options = {}) 122: add_column_sql = "ALTER TABLE #{table_name} ADD #{quote_column_name(column_name)} #{type_to_sql(type, options[:limit])}" 123: add_column_options!(add_column_sql, options) 124: execute(add_column_sql) 125: end
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 names, 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 colum +: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_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)
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# File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 186 186: def add_index(table_name, column_name, options = {}) 187: column_names = Array(column_name) 188: index_name = index_name(table_name, :column => column_names.first) 189: 190: if Hash === options # legacy support, since this param was a string 191: index_type = options[:unique] ? "UNIQUE" : "" 192: index_name = options[:name] || index_name 193: else 194: index_type = options 195: end 196: quoted_column_names = column_names.map { |e| quote_column_name(e) }.join(", ") 197: execute "CREATE #{index_type} INDEX #{quote_column_name(index_name)} ON #{table_name} (#{quoted_column_names})" 198: end
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)
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# File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 139 139: def change_column(table_name, column_name, type, options = {}) 140: raise NotImplementedError, "change_column is not implemented" 141: end
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 apppropriate SQL statement yourself.
Examples
change_column_default(:suppliers, :qualification, 'new') change_column_default(:accounts, :authorized, 1)
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# File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 149 149: def change_column_default(table_name, column_name, default) 150: raise NotImplementedError, "change_column_default is not implemented" 151: end
Returns an array of Column objects for the table specified by table_name. See the concrete implementation for details on the expected parameter values.
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# File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 28 28: def columns(table_name, name = nil) end
Creates a new table 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() yields a TableDefinition instance create_table(:suppliers) do |t| t.column :name, :string, :limit => 60 # Other fields here end
Regular form
create_table(:suppliers) add_column(:suppliers, :name, :string, {:limit => 60})
The options hash can include the following keys:
- :id
- Set to true or false to add/not add a primary key column automatically. Defaults to true.
- :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 or false 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_join ( category_id int, supplier_id int )
See also TableDefinition#column for details on how to create columns.
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# File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 90 90: def create_table(name, options = {}) 91: table_definition = TableDefinition.new(self) 92: table_definition.primary_key(options[:primary_key] || "id") unless options[:id] == false 93: 94: yield table_definition 95: 96: if options[:force] 97: drop_table(name) rescue nil 98: end 99: 100: create_sql = "CREATE#{' TEMPORARY' if options[:temporary]} TABLE " 101: create_sql << "#{name} (" 102: create_sql << table_definition.to_sql 103: create_sql << ") #{options[:options]}" 104: execute create_sql 105: end
Drops a table from the database.
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# File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 115 115: def drop_table(name) 116: execute "DROP TABLE #{name}" 117: end
Should not be called normally, but this operation is non-destructive. The migrations module handles this automatically.
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# File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 237 237: def initialize_schema_information 238: begin 239: execute "CREATE TABLE #{ActiveRecord::Migrator.schema_info_table_name} (version #{type_to_sql(:integer)})" 240: execute "INSERT INTO #{ActiveRecord::Migrator.schema_info_table_name} (version) VALUES(0)" 241: rescue ActiveRecord::StatementInvalid 242: # Schema has been intialized 243: end 244: end
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.
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# File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 7 7: def native_database_types 8: {} 9: end
Removes the column from the table definition.
Examples
remove_column(:suppliers, :qualification)
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# File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 130 130: def remove_column(table_name, column_name) 131: execute "ALTER TABLE #{table_name} DROP #{quote_column_name(column_name)}" 132: end
Remove the given index from the table.
Remove the suppliers_name_index in the suppliers table (legacy support, use the second or third forms).
remove_index :suppliers, :name
Remove the index named accounts_branch_id in the accounts table.
remove_index :accounts, :column => :branch_id
Remove the index named by_branch_party in the accounts table.
remove_index :accounts, :name => :by_branch_party
You can remove an index on multiple columns by specifying the first column.
add_index :accounts, [:username, :password] remove_index :accounts, :username
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# File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 212 212: def remove_index(table_name, options = {}) 213: execute "DROP INDEX #{quote_column_name(index_name(table_name, options))} ON #{table_name}" 214: end
Renames a column.
Example
rename_column(:suppliers, :description, :name)
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# File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 156 156: def rename_column(table_name, column_name, new_column_name) 157: raise NotImplementedError, "rename_column is not implemented" 158: end
Renames a table.
Example
rename_table('octopuses', 'octopi')
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# File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 110 110: def rename_table(name, new_name) 111: raise NotImplementedError, "rename_table is not implemented" 112: end
Returns a string of CREATE TABLE SQL statement(s) for recreating the entire structure of the database.
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# File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 232 232: def structure_dump 233: end
Truncates a table alias according to the limits of the current adapter.
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# File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 17 17: def table_alias_for(table_name) 18: table_name[0..table_alias_length-1].gsub(/\./, '_') 19: end
This is the maximum length a table alias can be
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# File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 12 12: def table_alias_length 13: 255 14: end