Data Retrieval on Informix

where

The where clause od the read ProcScript statement is supported. All text between the double quotation marks (") is inserted into the generated select instruction.

option

The option parameter of the read statement allows you to adjust various DBMS performance-related parameters, such as the maximum number of returned hits, the step size of a query, and the hit cache size.

selectdb

Informix handles the selectdb statement in all circumstances. However, the count function causes a separate select to be made for every field which is named in the selectdb statement. The same happens if you use the selectdb statement with no functions at all (you are transporting the last found value of the field or fields).

This can affect performance considerably. To avoid this, use the transport or count functions in separate selectdb statements; do not combine them with the other aggregate functions which are available (max, min, ave, and sum).

Field Subsetting

Fields which are not painted on the Uniface form and are not explicitly mentioned in ProcScript, are not selected, fetched, inserted, or updated by the DBMS connector. The Uniface kernel determines which fields are not required.

Note:  Field subsetting is allowed only in Informix OnLine. Field subsetting is not allowed in Informix Standard Engine (SE).

Open Cursors

The Informix connector supports up to 256 open cursors.