One common questions that we get from customers and partners is how to ingest data from Azure Log Analytics / Azure Sentinel to Azure Data Explorer from different reasons: joining data between different ADX clusters, longer retention period, heavy queries that aren't alight with LA limitations and etc.
There are many good articles in the web, here is a step by step guide and code from Sentinel team at GitHub which generates code to export data from selected tables in LA, create ADX tables with the right structure and mapping at update policies to adapt LA data structure to fit with ADX supported formats.
