Errors and Warnings from alter table

Most errors you encounter when running alter table inform you of schema constructs that prevent the requested command (for example, if you try to drop a column that is part of an index).

After you have changed the command to address any reported errors, set showplan and noexec to off so that SAP ASE actually performs the work.

All runtime data-dependent errors (for example, errors of numeric overflow, character truncation, and so on) can be identified only when the statement executes. Either change the command to fit the data available, or fix the data values to work with the required target datatypes the statement specifies. To identify these errors, run the command with noexec disabled.

• Errors and Warnings Generated by alter table modify
  Certain errors are generated only by the alter table modify command. Although alter table modify converts columns to compatible datatypes, alter table may issue errors if the columns you are converting have certain restrictions.
• Scripts Generated by if exists()...alter table
  Scripts that include certain constructs may produce errors if the table described in the script does not include the specified column.