12.21.5 How to change the definition of a compressed column (removing the compression specification for a column)

The column attribute change definition (CHANGE column-name) of the ALTER TABLE definition SQL statement cannot be used to change the definition of a compressed column. To change the definition of a compressed column, such as removing the compression specification or changing the split compression size, you must use the procedure below.

To change the definition of a compressed column:

  1. Unload the compressed table.
    Unload the compressed table whose definition is to be changed.
  2. Redefine the table.
    Use one of the following methods to redefine a table whose compression specification has been changed or removed:
    • Redefining the table
      Use DROP TABLE to delete the compressed table and then use CREATE TABLE to redefine the table whose compression specification was changed or removed.
    • Deleting and adding columns
      Use PURGE TABLE to remove all data from the table and then use the column deletion definition (DROP column-name) of ALTER TABLE to delete the compressed column. Next, use the column addition definition (ADD column-name) of ALTER TABLE to add the column whose compression specification was changed or removed.
      Note that the column addition definition of ALTER TABLE adds a column at the end of a table. Therefore, the compression specification can be changed or removed only for the last column.
  3. Reload the table
    Reload the unload data file that was unloaded in step 1 to the table that was defined in step 2.

For details about unloading and reloading data, see the manual HiRDB Version 9 Command Reference.