How to SELECT Rows
To solve above , we have three approaches:
- Subquery with INNER JOIN
- Correlated Subquery
- Window Function (available in MySQL 8.0 and later)
Subquery with INNER JOIN
INNER JOIN and subqueries are powerful ways to get related data under certain conditions. In this article, we will look at how to use INNER QUIRES with subqueries in SQL.
Syntax:
SELECT t1.*
FROM your_table t1
INNER JOIN (
SELECT partition_column, MAX(value_column) AS max_value
FROM your_table
GROUP BY partition_column
) t2 ON t1.partition_column = t2.partition_column AND t1.value_column = t2.max_value;
Example:
SELECT t1.*
FROM students t1
INNER JOIN (
SELECT class, MAX(score) AS max_score
FROM students
GROUP BY class
) t2 ON t1.class = t2.class AND t1.score = t2.max_score;
Output:
Explanation: The SQL query retrieves records from the “students” table where each record represents the student with the highest score (max_score) in their respective classes. The result includes details such as class, student ID, name, and score.
Correlated Subquery
Syntax:
SELECT t1.*
FROM your_table t1
WHERE value_column = (
SELECT MAX(value_column)
FROM your_table t2
WHERE t1.partition_column = t2.partition_column
);
Example:
SELECT t1.*
FROM students t1
WHERE score = (
SELECT MAX(score)
FROM students t2
WHERE t1.class = t2.class
);
Output:
Explanation: The SQL query selects records from the “students” table where each student has the maximum score in their respective class, resulting in a list of top-scoring students in each class.
Window Function
Syntax:
SELECT *
FROM (
SELECT *,
ROW_NUMBER() OVER (PARTITION BY partition_column ORDER BY value_column DESC) AS row_num
FROM your_table
) ranked
WHERE row_num = 1;
Example:
SELECT *
FROM (
SELECT *,
ROW_NUMBER() OVER (PARTITION BY class ORDER BY score DESC) AS row_num
FROM students
) ranked
WHERE row_num = 1;
Output:
Explanation: The SQL query retrieves records from the “students” table, showcasing the students with the highest scores in their respective classes.
How to SELECT Rows With MAX PARTITION By Another Column in MySQL
MySQL is a widely used relational database management system (RDBMS) that provides a robust and scalable platform for managing and organizing data. MySQL is an open-source software developed by Oracle Corporation, that provides features for creating, modifying, and querying databases. It utilizes Structured Query Language (SQL) to interact with databases, making it a popular choice for web applications and various software systems. MySQL’s versatility, reliability, and ease of use make it a preferred solution for developers and organizations seeking efficient data management capabilities.
In this article, you will learn about, How can SELECT rows with MAX(Column value), and PARTITION by another column in MySQL.
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