column

Instantiates a new column for the table. The type parameter must be one of the following values: :primary_key, :string, :text, :integer, :float, :decimal, :datetime, :timestamp, :time, :date, :binary, :boolean.

Available options are (none of these exists by default):

• :limit: Requests a maximum column length (:string, :text, :binary or :integer columns only)
• :default: The column’s default value. Use nil for NULL.
• :null: Allows or disallows NULL values in the column. This option could have been named :null_allowed.
• :precision: Specifies the precision for a :decimal column.
• :scale: Specifies the scale for a :decimal column.

Please be aware of different RDBMS implementations behavior with :decimal columns:

• The SQL standard says the default scale should be 0, :scale <= :precision, and makes no comments about the requirements of :precision.
• MySQL: :precision [1..63], :scale [0..30]. Default is (10,0).
• PostgreSQL: :precision [1..infinity], :scale [0..infinity]. No default.
• SQLite2: Any :precision and :scale may be used. Internal storage as strings. No default.
• SQLite3: No restrictions on :precision and :scale, but the maximum supported :precision is 16. No default.
• Oracle: :precision [1..38], :scale [-84..127]. Default is (38,0).
• DB2: :precision [1..63], :scale [0..62]. Default unknown.
• Firebird: :precision [1..18], :scale [0..18]. Default (9,0). Internal types NUMERIC and DECIMAL have different storage rules, decimal being better.
• FrontBase?: :precision [1..38], :scale [0..38]. Default (38,0). WARNING Max :precision/:scale for NUMERIC is 19, and DECIMAL is 38.
• SqlServer?: :precision [1..38], :scale [0..38]. Default (38,0).
• Sybase: :precision [1..38], :scale [0..38]. Default (38,0).
• OpenBase?: Documentation unclear. Claims storage in double.

This method returns self.

Examples

 # Assuming td is an instance of TableDefinition
 td.column(:granted, :boolean)
   #=> granted BOOLEAN

 td.column(:picture, :binary, :limit => 2.megabytes)
   #=> picture BLOB(2097152)

 td.column(:sales_stage, :string, :limit => 20, :default => 'new', :null => false)
   #=> sales_stage VARCHAR(20) DEFAULT 'new' NOT NULL

 def.column(:bill_gates_money, :decimal, :precision => 15, :scale => 2)
   #=> bill_gates_money DECIMAL(15,2)

 def.column(:sensor_reading, :decimal, :precision => 30, :scale => 20)
   #=> sensor_reading DECIMAL(30,20)

 # While <tt>:scale</tt> defaults to zero on most databases, it
 # probably wouldn't hurt to include it.
 def.column(:huge_integer, :decimal, :precision => 30)
   #=> huge_integer DECIMAL(30)