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= ODBC to Jet Data Type Mapping in our Data Access Drivers for Informix =

== Numeric Data Type Mappings in our Data Access Drivers for Informix ==

The table below details how the <nop>OpenLink data access drivers fetch numeric data from Informix. 

The SQL type reported for a {{{SELECT}}} column varies depending on the native Informix type of the column, its precision, and its scale. The C type used to fetch the data is also shown, together with the effect of the {{{JetFix}}} switch.

Changes to the type mappings required to implement the {{{JetFix}}} option are shown in italics.


**Table 1. Numeric Data Type Mappings**
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==Precision of C Data Types==

The C data 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, which has sufficient range to store the maximum numeric values supported by Informix.  However, {{{CTYPE_FLT64}}} may result in a loss of precision, if the precision of the data to be fetched exceeds 15 decimal digits.

**Table 2. Precision of C Data Types**
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== Informix Jetfix Testing ==

To verify the effect of the +jetfix switch, two tables were created and then linked into 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 3. Informix ODBC to Jet Data Type Mapping**
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