Changing a column definition

PointBase supports ALTER TABLE ALTER COLUMN functionality that allows some aspects of a column definition to be changed. In the case under discussion, a column which has been constrained as NOT NULL can be redefined to allow NULLs. The reverse is not allowed as some rows for the column may already have NULL values and it would be unclear as to what those values should become if the column definition changed to NOT NULL. In addition to changing a column from NOT NULL to NULL, some data types can be redefined to be wider than the existing defined width of the column, and for heap-organized tables the default value for a column can be changed. For full specifics on the use and limitations of ALTER TABLE ALTER COLUMN, please consult the PointBase Embedded documentation.