🔢 SQL COUNT() Function – Count Records in Your Tables

🧲 Introduction – What is SQL COUNT()?

The COUNT() function in SQL is used to count the number of rows returned by a query. It is one of the most commonly used aggregate functions and works with both numeric and non-numeric data.

🎯 In this guide, you’ll learn how to:

• Use COUNT() to count all rows or non-NULL values
• Count rows by group using GROUP BY
• Filter results with HAVING
• Understand the difference between COUNT(*), COUNT(column), and COUNT(DISTINCT column)

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✅ 1. Basic COUNT() Syntax

SELECT COUNT(*) FROM table_name;

✅ Counts all rows, including those with NULLs.

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🔍 2. COUNT(column) – Excludes NULLs

SELECT COUNT(email) FROM users;

✅ Counts only rows where email is not NULL.

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🆚 3. COUNT(*) vs COUNT(column)

Function	Description
COUNT(*)	Counts all rows, including NULLs
COUNT(column)	Counts only non-NULL values in the column

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🎯 4. COUNT(DISTINCT column)

SELECT COUNT(DISTINCT department) FROM employees;

✅ Counts unique departments only.

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📊 5. COUNT() with GROUP BY

SELECT department, COUNT(*) AS total_employees
FROM employees
GROUP BY department;

✅ Counts the number of employees per department.

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🔎 6. Filtering Counts with HAVING

SELECT department, COUNT(*) AS total
FROM employees
GROUP BY department
HAVING COUNT(*) > 10;

✅ Shows only departments with more than 10 employees.

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📘 Best Practices

✅ Recommended	❌ Avoid This
Use aliases for readable output	Leaving COUNT() column unnamed
Use COUNT(*) when counting all rows	Using COUNT(column) if NULLs exist
Use DISTINCT carefully with COUNT	Assuming COUNT() handles uniqueness by default

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📌 Summary – Recap & Next Steps

The COUNT() function is fundamental for SQL querying. It helps determine how many records exist, either in total or under certain conditions.

🔍 Key Takeaways:

• COUNT(*) counts all rows
• COUNT(column) ignores NULLs
• COUNT(DISTINCT col) counts unique values
• Combine with GROUP BY for grouped insights

⚙️ Real-World Relevance:
Used in reporting totals, dashboard KPIs, inventory counts, user activity tracking, and analytics.

➡️ Next: Explore CASE WHEN for conditional aggregation.

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❓ FAQ – SQL COUNT Function

❓ What does COUNT(*) count?

✅ It includes all rows, even if columns have NULLs.

❓ When should I use COUNT(column)?

✅ When you want to count only rows where that column has a value (non-NULL).

❓ Can I count distinct values?

✅ Yes, use COUNT(DISTINCT column_name).

❓ What is the difference between COUNT(*) and COUNT(1)?

✅ Functionally the same, but COUNT(*) is more readable and standard.

❓ Can I use COUNT() with JOINs?

✅ Absolutely. You can count joined rows or group counts per relationship.

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