rt_Lookup
Purpose
Returns a field value from a table in the context of a particular carrier.
Arguments
rt_Lookup(
<table name>
, <row select>
// See notes.
, <col name> // The column name.
)
Notes
The value is returned in an annotated string:
"<table name>[<row select><sep><col name><sep><value>]"
Where <sep> is an internal rules-engine marker (Chr$(149) ).
<table name> is resolved in the context of the current value of VEND_LABL.
<table name> parameter has been modified so that either a
“Table_Name” “Table_Name:Index_Name” can be used. “Index_Name” is optional. If it is not given (as has been true to this point), then “PrimaryKey” is assumed. In addition, this function can be passed fewer keys in the <row
select> parameter than are contained in the index being used. If fewer keys
are provided, then a Find_First where the provided keys are equal is performed.
For example, the first two keys of a three key index could be used. For
Collection_Create (and Driver), the resulting collection will be populated based on
all records which match the supplied keys (as was previously the case).
This function can limit its search one of several ways, keeping in mind that
“Lookup” routines find a single record (the first match), while “Collection” routines find all which match the request:
1. A simple value . . . which implies a single key search.
2. A list of values, such as
“[v1] [v2] [v3]” which implies a multi-key search even though the index may have more keys.
3. An SQL where clause using SELF! [ ] references.
4. A list of values (as in option 2) followed by
“ AND “ then an SQL where clause. For example: “[v1] [v2] AND SELF![MyFld] = ‘v3’”