1  DELETE_FIELD
   Deletes one or more field definitions. When the DELETE FIELD
   statement executes, Oracle Rdb deletes the field definition from the
   physical database. If you invoke the database using the PATHNAME
   argument, Oracle Rdb also deletes the field definition from the
   CDD$DATABASE definition of the database in the data dictionary.
   You can delete any named field, whether it was defined with a
   DEFINE FIELD statement or with a DEFINE RELATION statement.
   However, you cannot delete a field that is referred to in the
   definition of a relation, index, or constraint:

   Example:

   DELETE FIELD POSTAL_CODE.
 

2  More

   o  You must have the Oracle Rdb DELETE privilege for a field to
      delete the field with the DELETE FIELD statement.

   o  If you want to delete a field that is part of a relation
      definition, you must use the CHANGE RELATION statement to
      delete the field from the relation definition, or you must
      delete the entire relation.

   o  If you want to delete a field that is referred to in a
      constraint or index definition, you must first delete the
      constraint or index.

   o  You cannot delete a field definition unless you have invoked
      the database that includes the field.

   o  You can delete a field definition even when there are
      active users. Deleting a field definition will not affect
      active users until they exit their session and invoke the
      database the next time. By default, a database can be opened
      automatically (that is, by any user who invokes the database
      and executes a data manipulation language statement). If the
      database was modified so that it must be manually opened, the
      RMU/OPEN command must be used to open it.

   o  You must execute this statement in a read/write transaction.
      If there is no active transaction and you issue this
      statement, Oracle Rdb starts a read/write transaction implicitly.
 

2  Format

 (B)0DELETE FIELD qqqwqqq> field-name qqqqwqqq> .
                 mqqqq<qqqq , qqqq<qqqj

   field-name         The name of the field whose definition you
                      want to delete.
 

2  Examples
   Example 1

   Delete a single field definition:

   RDO> INVOKE DATABASE PATHNAME 'PERSONNEL'
   RDO> START_TRANSACTION READ_WRITE
   RDO> DELETE FIELD TEMP_NUM.
   RDO> COMMIT

   This sequence deletes the field definition from the physical
   database and the data dictionary.

   Example 2

   Delete more than one field definition:

   RDO> INVOKE DATABASE PATHNAME 'PERSONNEL'
   RDO> START_TRANSACTION READ_WRITE
   RDO> DELETE FIELD TEMP_NUM, MONEY.
   RDO> COMMIT

   This sequence deletes the definitions for the TEMP_NUM and MONEY
   fields from the physical database and the data dictionary.

   Example 3

   Delete a field from a relation:

   RDO> INVOKE DATABASE PATHNAME 'PERSONNEL'
   RDO> START_TRANSACTION READ_WRITE
   RDO> DELETE FIELD STATUS_NAME.
   %RDO-W-NOCDDUPDAT, database invoked by filename, the data dictionary will not be updated
   %RDB-E-NO_META_UPDATE, metadata update failed
   %RDMS-F-RELEXI, field STATUS_NAME is used in relation, WORK_STATUS
   -RDMS-F-FLDNOTDEL, field STATUS_NAME has not been deleted
   RDO> CHANGE RELATION WORK_STATUS.
   cont>  DELETE STATUS_NAME.
   cont>  END.
   RDO> DELETE FIELD STATUS_NAME.
   RDO> COMMIT

   If a field is used in a relation, you need to perform two
   operations to delete it:

   o  Change the relation by deleting the field.

   o  Delete the global field definition.