<docbook><section><title>InformixODBCJetMapping</title><para> </para><title> ODBC to Jet Data Type Mapping in our Data Access Drivers for Informix </title> ODBC to Jet Data Type Mapping in our Data Access Drivers for Informix 
<bridgehead class="http://www.w3.org/1999/xhtml:h2"> Numeric Data Type Mappings in our Data Access Drivers for Informix </bridgehead>
<para>The table below details how the OpenLink data access drivers fetch numeric data from Informix.</para><para>The SQL type reported for a <computeroutput>SELECT</computeroutput> 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 <computeroutput>JetFix</computeroutput> switch.</para><para>Changes to the type mappings required to implement the <computeroutput>JetFix</computeroutput> option are shown in italics.</para><para> <emphasis>Table 1.
 Numeric Data Type Mappings</emphasis> <figure><graphic fileref="InformixODBCJetMapping/InformixAgentNumericMappings.png" /></figure></para><bridgehead class="http://www.w3.org/1999/xhtml:h2">Precision of C Data Types</bridgehead>
<para>The C data type used to fetch a numeric value is determined by the maximum precision supported by the type.</para><para>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.</para><para>If a numeric type capable of supporting the required precision does not exist, then the data is fetched in character form, unless the <computeroutput>JetFix</computeroutput> switch is on.
 In this case, the data is fetched using the <computeroutput>CTYPE_FLT64</computeroutput> fetch type, which has sufficient range to store the maximum numeric values supported by Informix.
 However, <computeroutput>CTYPE_FLT64</computeroutput> may result in a loss of precision, if the precision of the data to be fetched exceeds 15 decimal digits.</para><para><emphasis>Table 2.
 Precision of C Data Types</emphasis>  <figure><graphic fileref="InformixODBCJetMapping/InformixOpenLinkCTypes.png" /></figure></para><bridgehead class="http://www.w3.org/1999/xhtml:h2"> Informix Jetfix Testing </bridgehead>
<para>To verify the effect of the +jetfix switch, two tables were created and then linked into Access -- once with <computeroutput>JetFix</computeroutput> enabled, and once with <computeroutput>JetFix</computeroutput> disabled.</para><para>The first table contained five <computeroutput>MONEY</computeroutput> columns of various precisions and scales.</para><para>The second table was identical except that it used <computeroutput>DECIMAL</computeroutput> instead of <computeroutput>MONEY</computeroutput> columns.</para><para>The resulting Jet data type mappings as shown in the &#39;<computeroutput>Table Design</computeroutput>&#39; view are detailed below:</para><para><emphasis>Table 3.
 Informix ODBC to Jet Data Type Mapping</emphasis> <figure><graphic fileref="InformixODBCJetMapping/InformixODBCJetMapping.png" /></figure> </para></section></docbook>