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SELECT Queries

5 min read Quiz at the end

SELECT retrieves data. List specific columns instead of SELECT *. Use AS for aliases, DISTINCT to remove duplicates, and expressions like price * 1.18 AS price_with_tax for computed columns in the query.

SELECT Basics

SELECT * FROM users;
SELECT name, email FROM users;
SELECT name AS user_name FROM users;
SELECT DISTINCT age FROM users;
SELECT COUNT(*) FROM users;

Calculated columns

SELECT name, age + 1 AS next_birthday FROM users;

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Topic Quiz · 5 questions

Test your understanding before moving on

1. Which keyword removes duplicate rows?

💡 SELECT DISTINCT removes duplicate values from the result set.

2. How do you rename a column in SELECT output?

💡 The AS keyword creates an alias for a column in the result.

3. Which function counts all rows?

💡 COUNT(*) counts every row, including those with NULLs.

4. Which clause returns only certain columns?

💡 The SELECT clause specifies which columns to return.

5. Which clause specifies the table?

💡 The FROM clause specifies which table to query.

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SELECT Queries

SELECT Basics

Calculated columns

Test your understanding before moving on