Structure Command Group
Commands
- create_field
- output_aux_file
- create_index
- set_relate
- delete_field
- structure_abort
- delete_index
- structure_copy
- field_map
- structure_end
- load_def
- structure_start
- make_file
The Structure group provides the means for creating tables from running programs without the requirement to rely on any table definition defined outside the program. It is possible using these commands to specify virtually every aspect of a table besides the actual data in the table. The same capabilities they offer for creation of tables are also usable for modifying existing tables, including both addition and deletion of columns, indexes, and index segments. Finally, to complement the group's capabilities in specifying the attributes of tables and their components, there is a parallel capability in querying the existing state of the same attributes in existing tables.
Most structuring and restructuring of tables is done within a block begun by a structure_start command and terminated by a structure_end command. Within this block, attributes are set by the set_attribute command and queries by the get_attribute command. Neither of these last two commands is in the Structure group, however, because they are used for the setting and querying of attributes generally, not just those of tables and their components.
Structure operations can be abandoned, or cancelled, by use of the structure_abort command, which undoes all operations in a structure block if the command is executed before structure_end is executed. Structure operations can be based on the structure attributes of an existing table by use of the structure_copy command. Columns and indexes can be added or deleted by the use of individual commands for deletion or creation.
All commands in this group other than structure_..., create_..., and delete_... can be executed outside structure blocks, and those that can change attributes (file_size, make_file, set_relate) should not be executed inside structure blocks.