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SQL - Coggle Diagram
SQL
1. The "Reverse Engineering" Phase
Define the Grain
What does one single row in your final table represent?
Sketch the Schema
Literally draw the columns you need
Identify the "Must-Haves"
Which metrics are aggregations (sums, averages) and which are attributes (names, dates)?
2. The "Source-to-Target" Mapping
The Anchor Table
Identify which table contains the primary "grain" you defined in Step 1. This is your
FROM
clause.
The Join Strategy:
One-to-One
Simple Join
One-to-Many
Be careful! This will duplicate rows in your anchor table.
Missing Data
Do you need a LEFT JOIN to keep all records from your anchor even if there’s no match?
The Execution Order (The "SQL Mindset")
FROM/JOIN: Gather the raw materials.
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