The mapping prefix is used to create a mapping table that can be used to, for example, replacing field values and field names during script execution.
Syntax:
Mapping( loadstatement | selectstatement )
The mapping prefix can be put in front of a LOAD or a SELECT statement and will store the result of the loading statement as a mapping table. Mapping provides an efficient way to substituting field values during script execution, e.g. replacing US, U.S. or America with USA. A mapping table consists of two columns, the first containing comparison values and the second containing the desired mapping values. Mapping tables are stored temporarily in memory and dropped automatically after script execution.
The content of the mapping table can be accessed using e.g. the Map … Using statement, the Rename Field statement, the Applymap() function or the Mapsubstring() function.
Example:
In this example we load a list of salespersons with a country code representing their country of residence. We use a table mapping a country code to a country to replace the country code with the country name. Only three countries are defined in the mapping table, other country codes are mapped to 'Rest of the world'.
The resulting table looks like this:
| Salesperson | Country |
|---|---|
| John | Sweden |
| Mary | Sweden |
| Per | Sweden |
| Preben | Denmark |
| Olle | Denmark |
| Ole | Norway |
| Risttu | Rest of the world |