Review Retention SQL

[andreabringhurst]

• Read through all the SQL code.
• Identify the purpose and functionality of each query.
• Note any immediate issues or areas for improvement.
• Create consistency in the queries in both structure and output.
• Add comments explaining the purpose of each query.
• Document any assumptions or dependencies.

[andreabringhurst]

This is now ready in pull request #42 .

[andreabringhurst]

This will be completed when the pull request #42 is complete.