ODBC to Jet Data Type Mapping

Informix Jet Support

Informix Jetfix Testing

To verify the effect of the +jetfix switch, two tables were created and then linked to from Access, once with +jetfix enabled, and once with +jetfix disabled. The first table contained five MONEY columns of various precisions and scales. The second table was identical except that it used DECIMAL instead of MONEY columns. The resulting Jet data type mappings as shown in the 'Table Design' view are detailed below:

Table: 1. Informix ODBC to Jet Data Type Mapping

OpenLink Informix Agent Numeric Data type Mappings

The following table details how the Informix agent fetches numeric data from Informix. The SQL type reported for a SELECT column varies depending on the native Informix type of the column, and its precision and scale. The OpenLink C type used to fetch the data is also shown, together with the effect of the JetFix command line switch.

Changes to the type mappings required to implement the +jetfix option are shown in italics.

Table: 2. Informix Agent Numeric Data type Mappings

Precision of OpenLink C Types

The choice of OpenLink C type used to fetch a numeric value is determined by the maximum precision supported by the type. If a numeric type exists which can represent the data to be fetched, without loss of precision, then this is used as the preferred fetch type. If a numeric type capable of supporting the required precision does not exist, then the data is fetched in character form, unless the JetFix switch is on. In this case, the data is fetched using the CTYPE_FLT64 fetch type. This type has sufficient range to store the maximum numeric values supported by Informix, but its use may result in a loss of precision, if the precision of the data to be fetched exceeds 15 decimal digits.

Table: 3. Precision of OpenLink C Types