Appendix B. Reserved Words for IBM Informix Extended Parallel Server

The ISO standard SQL language has many keywords. Some are designated as reserved words and others as non-reserved words. In ISO SQL, reserved words cannot be used as identifiers for database objects (like tables, columns, and so forth). To use such a name in a valid SQL statement requires a delimited identifier (Delimited Identifiers) that you enclose between double ( " " ) quotation marks.

By contrast, the dialect of SQL that IBM Informix database servers implement has very few reserved words in the sense of a character string that obeys the rules for identifiers (Identifier) but always produces a compilation error or runtime error when used as an identifier. Your application might encounter restricted functionality, however, or unexpected results, if you define an SPL routine that has the same name as a built-in SQL function, expression, or operator.

This appendix lists the keywords in the IBM Informix implementation of SQL for Extended Parallel Server. Do not declare any of these keywords as SQL identifiers. If you do, errors or syntactic ambiguities can occur if the identifier appears in a context where the keyword is valid. In addition, your code will be more difficult to read and to maintain. Do not use keywords of C or C++ (nor of any other programming language that you will be using in an embedded mode) in your database structures.

If you receive an error message that seems unrelated to the SQL statement that caused the error, you might wish to review this appendix to see if a keyword has been used as an identifier.

To avoid using a keyword as an identifier, you can qualify the identifier with an owner name or modify the identifier. For example, rather than name a database object CURRENT, you might name it o_current or 'juanita'.current. For a discussion of potential problems in using keywords as identifiers, and of additional workarounds for specific keywords, see Use of Keywords as Identifiers. See also IBM Informix Guide to SQL: Tutorial for more information about using keywords as identifiers in SQL applications.