Mapping Fields

Introduction

Identifying how to populate the target fields during a migration is a key task in any project and can be complex. In some cases, the value you need to use may not be on the source form but stored somewhere else on the source server. In some cases, you may need to construct the value using several different source fields. There may be also a source field that performs the same function, but has a different set of values to those on the target.

Precision Bridge has mappings that will handle all of these situations and more.

Field Mapping Types

There are 5 basic field mapping types in Precision Bridge. It is important to understand which one to use to meet your needs. Use the links below to find out more about each type.

Field Mapping Type	Usage
Simple	This is as simple as it gets. Identify the source field that will provide the value for the target. The value will be migrated 'as is' with no other transformation. Simple mappings can also be used to set the target field to a constant (default) value.
Value Match	Imagine you have a target field that has a defined set of values it can have (e.g. a pick list) You have identified a similar field on the source, but the values are different. A simple mapping will not work here, we need to map each possible source value to a target value. This is what the value match mapping can do.
Assignment	What if you want to extract a part of a source field's value to use as a target? Or concatenate multiple values together to make the target value? Or perform a numeric calculation to get the final value? Or some even more complicated transformation? Assignment mappings are made for this. You build an expression that can include source fields, constant values, operators as well as the many assignment functions that Precision Bridge provides. This expression is calculated at execution time to build the target value.
Lookup	What should you do if the value you want to use for the target is not even on the source form? Maybe it is stored in a configuration form and referenced via its ID on the source record? You need the lookup mapping. You can build a query to extract a record from any source or target table and then populate the target field with the value of one of the fields on this table.
Reference Mapping	What if both the source record and the target record reference a value by its id, but the id is totally different? You can use the reference mapping. This relies on defining the correlation between the referenced record via one or more common values. This information can be used to identify the id of a target record given the id of the source record. For example, on the source record, the 'assigned to' value is an id reference to a user record. The target 'assigned to' value is also an id reference to a user record. The user record can be correlated by the email value. The reference mapping will get the email of the source user and use this to get the id of the matching user on the target. Reference mappings cache correlated results, often resulting in a far more perfomance efficient mapping.

In ServiceNow -> ServiceNow instance migrations, there are two further mapping types that can be used. ID List mappings and ID Replacement Mappings

Video Tutorial - Field Mapping Types