coalesce.md

📚 COALESCE

The COALESCE function is used in SQL to return the first non-NULL value in a list of expressions.
It is helpful for handling missing or default values in queries.

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🛠️ Basic Syntax

SELECT COALESCE(expression1, expression2, ..., default_value)
FROM table_name;

• COALESCE evaluates each expression in order and returns the first that is not NULL.
• If all expressions are NULL, it returns the specified default value.

Example

SELECT first_name, COALESCE(phone_number, 'No Phone') AS contact_info
FROM employees;

• This query returns each employee’s phone number, or 'No Phone' if none exists.

Key Points

• COALESCE is often used for data cleanup and display formatting.
• It can take two or more arguments.
• Useful in SELECT statements, WHERE clauses, or even UPDATE operations.

Additional Example

SELECT customer_name, COALESCE(email, 'No Email Provided') AS email_contact
FROM customers;

• This query provides a fallback text if a customer’s email is missing.

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🎥 Video Notes

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📝 Problem Description

Describe the problem, challenge, or topic discussed in a video related to SELECT FROM.
What concept was explained or what exercise was solved?

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DataBase Given

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💻 My SQL Code

-- Write your SQL code attempt or solution related to SQL COMMAND
SQL COMMAND

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🧠 Solution Code / Explanation

SQL COMMAND

Explanation - Explain what you learned, any key takeaways, or how you solved the problem related to COMMAND._

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