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deck

1. Core Topics We Covered

This course emphasized practical SQL for real-world tasks. Here’s a quick look at the key topics you’ve mastered:

Category	SQL Features Used
Filtering	WHERE, AND, OR, IN, BETWEEN
Sorting & Limits	ORDER BY, LIMIT
Aggregation	COUNT, SUM, AVG, ROUND
Grouping	GROUP BY, HAVING
Joins	INNER JOIN, LEFT JOIN
Subqueries	In WHERE, HAVING, and SELECT clauses
Logic & Control	CASE, IS NULL, date grouping (STRFTIME)

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2. Where Each Concept Shined

Concept	Real-Life Use Case Example
JOIN	Merging orders with customer data
GROUP BY	Summarizing product categories or appointment counts
LEFT JOIN	Finding clients who never purchased
HAVING	Filtering groups (e.g. customers who spent > $400)
CASE	Splitting data into segments (e.g. urgent vs routine)
Subquery	Comparing with average metrics (e.g. price, sales)

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3. Debugging Patterns You Faced

As queries got more complex, you learned to catch issues like:

• Incorrect joins (e.g. wrong key or join type)
• Missing GROUP BY with aggregates
• Filters applied in the wrong stage (WHERE vs HAVING)
• Syntax that worked but returned the wrong results

Debugging isn't just fixing — it's about aligning logic with purpose.

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4. Application Contexts

You've touched datasets from:

• Online retail → product, stock, orders
• Delivery logistics → drivers, regional trends
• Event ticketing → purchases, high spenders
• Hospital systems → visits, time-based metrics

Each domain showed how data structure shapes query design.

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5. Building Analyst Mindset

Think beyond queries—ask:

• What insight does this result offer?
• Could this scale with more data?
• Is the logic understandable to someone else on my team?

You're not just writing code—you're writing analysis.

That’s what true SQL mastery looks like.

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