SQL Tutorial - Transform Table Structure | SQL Pivot table | CASE statement in SQL
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Title: SQL Tutorial: Transforming Table Structure with CASE Statements
Description: Learn how to transform table structure with CASE statements in SQL. This tutorial covers the basics of using MAX() function with CASE statements to pivot data and convert rows to columns. It includes step-by-step explanations and practical examples of how to use this technique to create summary reports in a more efficient way.
SQL, CASE statement, MAX function, pivot table, transform table, rows to columns, summary report, SQL tutorial.
CREATE TABLE event_data (
date DATE,
count INT,
event VARCHAR(20)
);
INSERT INTO event_data (date, count, event)
VALUES
('2023-03-29', 10, 'Impression'),
('2023-03-29', 2, 'Click'),
('2023-03-29', 1, 'Login'),
('2023-03-31', 12, 'Impression'),
('2023-03-31', 3, 'Click'),
('2023-03-31', 0, 'Login'),
('2023-04-01', 13, 'Impression'),
('2023-04-01', 4, 'Click'),
('2023-04-01', 3, 'Login');
SELECT
Date,
MAX(CASE WHEN Event = 'Impression' THEN Count ELSE 0 END) AS Impression,
MAX(CASE WHEN Event = 'Click' THEN Count ELSE 0 END) AS Click,
MAX(CASE WHEN Event = 'Login' THEN Count ELSE 0 END) AS Login
FROM table_name
GROUP BY Date;
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