Approaching complex queries

Writing complex SQL queries can be a challenging task, especially when dealing with multiple tables, complex filtering conditions, and intricate calculations. However, by following a step-by-step approach, you can break down the problem into smaller, manageable parts and gradually build up to the final query.

Here are some systematic guidelines on how to approach complex queries:

• Step 1 – define the objective: Begin by clearly defining the objective of your query. What specific information are you trying to retrieve or calculate? What is the desired output?
• Step 2 – identify the tables: Determine which tables contain the necessary data for your objective and identify their respective keys. This helps us identify our starting point. If multiple tables are involved, consider the relationships between them and how they should be joined. Determine the key(s) in each table.
• Step 3 – determine the filtering criteria: Identify...