ADD Column Clause

Use the ADD Column clause to add a column to a table, and to define constraints on the new column. This clause can also associate a security policy with a table that has no security policy, or can specify a security label for the new column, if the table already has a security policy.

This syntax fragment is part of the ALTER TABLE statement.

ADD Column Clause

New Column

Notes:

¹ See Data Type
² Use this path no more than once
³ See DEFAULT clause of ALTER TABLE
⁴ See Single-Column Constraint Format
⁵ See BEFORE Clause
⁶ See Add column SECURED WITH label clause


Element	Description	Restrictions	Syntax
column	Name of column before which new_column is to be placed	Must already exist in the table	Identifier
new_column	Name of column that you are adding	You cannot add a serial column if the table contains data	Identifier

The following restrictions apply to the ADD clause:

You cannot add a serial column to a table that contains data.
You cannot add columns beyond the maximum row size of 32,767 bytes.

Restrictions on adding columns of type IDSSECURITYLABEL

The following restrictions affect the use of the ADD Column clause to add a column of the IDSSECURITYLABEL data type to support a label-based access control (LBAC) security policy:

If the table has no security policy, a user who holds the DBSECADM role must also include the ADD SECURITY POLICY keywords to specify an LBAC security policy, as in this example:

CREATE TABLE tA
   (Col_1 BIGINT
    Col_2 INTERVAL(YEAR TO MONTH);  
    Col_3 VARCHAR (255));  
 . . .
ALTER TABLE tA
  ADD (Col_4 IDSSECURITYLABEL DEFAULT 'label4'), --to add this column 
  ADD SECURITY POLICY Watchdog;   --a security policy is also required
                              -- and 'label4' must be a Watchdog label

Only a user who holds the DBSECADM role can add a column of type IDSSECURITYLABEL.
A table can have at most one column of type IDSSECURITYLABEL.
The IDSSECURITYLABEL column cannot have SECURED WITH column protection.
The IDSSECURITYLABEL column has an implicit NOT NULL constraint by default. If no label name for the default security label is specified in the DEFAULT clause, the default value for this column is the security label for write access that is held by the current user.
The IDSSECURITYLABEL column cannot have any explicit single-column constraints, and it cannot be part of multiple-column referential or check constraints.

For the ALTER TABLE syntax to add or drop row-level LBAC protection for the table, see SECURITY POLICY Clause.

For the ALTER TABLE syntax to add column-level protection for a new column in a table already protected by an LBAC security policy, see Add column SECURED WITH label clause.

For the ALTER TABLE syntax to add or drop column-level LBAC protection for an existing column, see Modify Column Security clause.