Drop unneeded columns
Rename columns
Reposition columns
Add AutoNumber column
Add or change Defaults
Add or change NULL / NOT NULL constraints
Change a column’s data type - except increasing the length of a VARCHAR column
Notes:
Some data type changes will cause loss of data and possible numeric overflows.
When renaming columns, any dependent views or triggers (not created by Scriptoria) that reference the old column name will compile with errors and need to be manually amended. Application programs may also be affected.
Columns can only be changed to NOT NULL when a “Default” is defined unless the table is empty.
Although Access will allow you to add constraints that violate existing data, DB2 does not.
As a general rule, if Access issues an error message when changing a “Required” field or Validation Rule, this change will not be permitted by DB2.