diff options
Diffstat (limited to 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb')
-rw-r--r-- | activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb | 81 |
1 files changed, 75 insertions, 6 deletions
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb index d3fbc18f97..d5f8dbc8fc 100644 --- a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb +++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb @@ -446,12 +446,81 @@ module ActiveRecord execute "DROP TABLE#{' IF EXISTS' if options[:if_exists]} #{quote_table_name(table_name)}" end - # Adds a new column to the named table. - # See TableDefinition#column for details of the options you can use. - # - # Note: Not all options will be available, generally this command should - # ignore most of them. In favor of doing a low-level call to simply - # create a column. + # Add a new +type+ column named +column_name+ to +table_name+. + # + # The +type+ parameter is normally one of the migrations native types, + # which is one of the following: + # <tt>:primary_key</tt>, <tt>:string</tt>, <tt>:text</tt>, + # <tt>:integer</tt>, <tt>:bigint</tt>, <tt>:float</tt>, <tt>:decimal</tt>, + # <tt>:datetime</tt>, <tt>:time</tt>, <tt>:date</tt>, + # <tt>:binary</tt>, <tt>:boolean</tt>. + # + # You may use a type not in this list as long as it is supported by your + # database (for example, "polygon" in MySQL), but this will not be database + # agnostic and should usually be avoided. + # + # Available options are (none of these exists by default): + # * <tt>:limit</tt> - + # Requests a maximum column length. This is number of characters for a <tt>:string</tt> column + # and number of bytes for <tt>:text</tt>, <tt>:binary</tt> and <tt>:integer</tt> columns. + # * <tt>:default</tt> - + # The column's default value. Use nil for NULL. + # * <tt>:null</tt> - + # Allows or disallows +NULL+ values in the column. This option could + # have been named <tt>:null_allowed</tt>. + # * <tt>:precision</tt> - + # Specifies the precision for a <tt>:decimal</tt> column. + # * <tt>:scale</tt> - + # Specifies the scale for a <tt>:decimal</tt> column. + # + # Note: The precision is the total number of significant digits + # and the scale is the number of digits that can be stored following + # the decimal point. For example, the number 123.45 has a precision of 5 + # and a scale of 2. A decimal with a precision of 5 and a scale of 2 can + # range from -999.99 to 999.99. + # + # Please be aware of different RDBMS implementations behavior with + # <tt>:decimal</tt> columns: + # * The SQL standard says the default scale should be 0, <tt>:scale</tt> <= + # <tt>:precision</tt>, and makes no comments about the requirements of + # <tt>:precision</tt>. + # * MySQL: <tt>:precision</tt> [1..63], <tt>:scale</tt> [0..30]. + # Default is (10,0). + # * PostgreSQL: <tt>:precision</tt> [1..infinity], + # <tt>:scale</tt> [0..infinity]. No default. + # * SQLite2: Any <tt>:precision</tt> and <tt>:scale</tt> may be used. + # Internal storage as strings. No default. + # * SQLite3: No restrictions on <tt>:precision</tt> and <tt>:scale</tt>, + # but the maximum supported <tt>:precision</tt> is 16. No default. + # * Oracle: <tt>:precision</tt> [1..38], <tt>:scale</tt> [-84..127]. + # Default is (38,0). + # * DB2: <tt>:precision</tt> [1..63], <tt>:scale</tt> [0..62]. + # Default unknown. + # * SqlServer?: <tt>:precision</tt> [1..38], <tt>:scale</tt> [0..38]. + # Default (38,0). + # + # == Examples + # + # add_column(:users, :picture, :binary, limit: 2.megabytes) + # # ALTER TABLE "users" ADD "picture" blob(2097152) + # + # add_column(:articles, :status, :string, limit: 20, default: 'draft', null: false) + # # ALTER TABLE "articles" ADD "status" varchar(20) DEFAULT 'draft' NOT NULL + # + # add_column(:answers, :bill_gates_money, :decimal, precision: 15, scale: 2) + # # ALTER TABLE "answers" ADD "bill_gates_money" decimal(15,2) + # + # add_column(:measurements, :sensor_reading, :decimal, precision: 30, scale: 20) + # # ALTER TABLE "measurements" ADD "sensor_reading" decimal(30,20) + # + # # While :scale defaults to zero on most databases, it + # # probably wouldn't hurt to include it. + # add_column(:measurements, :huge_integer, :decimal, precision: 30) + # # ALTER TABLE "measurements" ADD "huge_integer" decimal(30) + # + # # Defines a column with a database-specific type. + # add_column(:shapes, :triangle, 'polygon') + # # ALTER TABLE "shapes" ADD "triangle" polygon def add_column(table_name, column_name, type, options = {}) at = create_alter_table table_name at.add_column(column_name, type, options) |