SQL Server Setup Help

SQL Server Setup Help


Defaults specify what values are used in a column if you do not specify a value for the column when inserting a row. Defaults can be anything that evaluates to a constant, such as:

  • Constant

  • Built-in function

  • Mathematical expression

There are two ways to apply defaults:

  • Create a default definition using the DEFAULT keyword in CREATE TABLE to assign a constant expression as a default on a column.

    This is the preferred, standard method. It is also the more concise way to specify a default.

  • Create a default object using the CREATE DEFAULT statement and bind it to columns using the sp_bindefault system stored procedure.

    This is a backward compatibility feature.

This example creates a table using one of each type of default. It creates a default object to assign a default to one column, and binds the default object to the column. It then does a test insert without specifying values for the columns with defaults and retrieves the test row to verify the defaults were applied.

USE pubs
CREATE TABLE test_defaults
   (keycol      smallint,
   process_id   smallint DEFAULT @@SPID,   --Preferred default definition
   date_ins   datetime DEFAULT getdate(),   --Preferred default definition
   mathcol      smallint DEFAULT 10 * 2,   --Preferred default definition
   char1      char(3),
   char2      char(3) DEFAULT 'xyz') --Preferred default definition
/* Illustration only, use DEFAULT definitions instead.*/
CREATE DEFAULT abc_const AS 'abc'
sp_bindefault abc_const, 'test_defaults.char1'
INSERT INTO test_defaults(keycol) VALUES (1)
SELECT * FROM test_defaults

The output of this sample is:

Default bound to column.

(1 row(s) affected)

keycol process_id date_ins                    mathcol char1 char2 
------ ---------- --------------------------- ------- ----- ----- 
1      7          Oct 16 1997  8:34PM         20      abc   xyz   

(1 row(s) affected)

See Also


Creating and Modifying a Table