Table Definition Requirements

• Tables must contain IFIL and DODA structures. These can be added after the fact for existing files and are inserted automatically for files created by c-treeDB and c-treeACE SQL.
• The ISAM application must use the c-tree Plus data types (as defined in the DODA) as in the c-tree - SQL data type mapping. For example a CT_CHAR is used in the SQL to store a 1-byte integer.

  Note: There is an incompatibility between the use of CT_ARRAY in the current c-tree Plus ODBC Driver and the use of CT_ARRAY in c-treeDB and c-c-treeACE SQL, including the c-treeACE SQL ODBC Driver.

• The table must have either TRNLOG or PREIMG in its file mode to use the ROLLBACK WORK and integrity constraint capabilities.
• Superfiles are not supported by c-treeACE SQL.
• To properly handle NULL, the table must contain the $NULFLD$ field, a hidden field generated by c-treeDB at creation time. Tables created with the c-treeDB Interface (used under c-treeACE SQL) have a hidden field, $NULFLD$, which is used to determine if each user-created field in the record buffer has a NULL value. c-treeACE SQL requires this capability to implement constraints. c-treeDB and c-treeACE SQL will access tables without the $NULFLD$ field, but the table’s fields will always return a non-NULL status.
• To properly handle JOINS referencing ROWID, the table should contain the $ROWID$ field (a hidden field generated by the c-treeDB at creation time). c-treeDB and c-treeACE SQL should work with tables without the $ROWID$ field, and will use the record offset as the ROWID tuple identifier. SQL statements like “select * from table where ROWID > ‘4’” will fail because using record offset as ROWID will give us record offsets instead of sequential numbers.

  Note: When c-tree updates a variable length record, the record offset for the record may change if the updated record size is larger than the original record. In this particular case, the ROWID for this ROW will not be unique, as required by the SQL standard.