Restrictions to xfODBC’s support of SQL
The following are some of the restrictions to xfODBC’s support of SQL. For more, see the Connectivity Series release notes (REL_CONN.TXT) and the Synergy/DE restrictions file (RESTRICT.TXT).
- The ORDER BY column must be referenced by SELECT column position when accompanied by a GROUP BY clause. See ORDER BY.
- GROUP BY is not supported for UNION clauses.
- Columns specified in a GROUP BY clause must be included in the select list and columns specified in the select list must be included in the GROUP BY clause. See GROUP BY for information.
- Only one ORDER BY clause is allowed with a UNION, and this must follow the final SELECT statement. An ORDER BY clause in a UNION applies to the entire result set.
Additionally, xfODBC does not support the following:
- Field‑level access controls. (Instead, xfODBC enables you to set access levels for tables and groups, which determine the access levels for users. See Setting security levels.)
- ALTER TABLE
- CREATE INDEX (supported after the initial CREATE TABLE and before the first INSERT, but at no other time)
- DROP INDEX
- Expressions in ORDER BY column
- “FROM” in the UPDATE [FROM] command
- Multi‑table updates
- ROW_NUMBER and the OVER clause