Grouping Results - SQL

SELECT id, instanceId, processModelId, GROUP_CONCAT(CONCAT_WS("=", variableName, oldValue)) AS OLDVALUE,
GROUP_CONCAT(CONCAT_WS("=", variableName, newValue)) AS NEWVALUE , parentVariableName  FROM `Object_History`  
GROUP BY instanceId, parentVariableName;

This shows how to group the expanded individual fields of a CDT in a single row

You will need to take care of the length of the Strings. The concatenation may produce strings which are very long. You need to set some limit especially in case of arrays - about how many variables you are going to edit etc.

A better version:

SELECT id, instanceId, processModelId, GROUP_CONCAT(CONCAT_WS("=", variableName, oldValue) SEPARATOR ", ") AS OLDVALUE,
GROUP_CONCAT(CONCAT_WS("=", variableName, newValue) SEPARATOR ", ") AS NEWVALUE , parentVariableName FROM Object_History
GROUP BY instanceId, parentVariableName;