Method: UpdateBeforeValue
Function name: UpdateBeforeValue
Parameter list: (SourceColumnType)
Return type: SourceColumnType
What the method does: Returns the before-image value for an UPDATE operation that changes the source column value. For DELETE and INSERT operations, and for an UPDATE operation that changes the value of the specified column to the same value, the returned value is a NULL.
Note: When this method is used, the Source Data value on the Mapping page must be a source column name. The input parameter type you specify in the expression workbox must match the source column type. This will also be the return type of the method, and it must be CHAR, INT, DECIMAL, or DOUBLE.