Home Database Mysql Tutorial SQL JOIN: WHERE vs. ON: What's the Key Difference in Filtering Joined Data?

SQL JOIN: WHERE vs. ON: What's the Key Difference in Filtering Joined Data?

Jan 23, 2025 am 02:49 AM

SQL JOIN: WHERE vs. ON: What's the Key Difference in Filtering Joined Data?

SQL JOIN: Understanding WHERE and ON Clauses

Mastering SQL JOINs requires a clear understanding of the WHERE and ON clauses. While sometimes interchangeable, their functions differ significantly.

WHERE Clause: Post-Join Filtering

The WHERE clause filters the results of a join. Consider this example:

SELECT *
FROM Orders
LEFT JOIN OrderLines ON OrderLines.OrderID = Orders.ID
WHERE Orders.ID = 12345;
Copy after login

Here, the WHERE clause filters the output, showing only rows where Orders.ID is 12345. This applies after the LEFT JOIN has combined data from Orders and OrderLines.

ON Clause: Join Condition Definition

The ON clause defines the join condition itself. Observe:

SELECT *
FROM Orders
LEFT JOIN OrderLines ON OrderLines.OrderID = Orders.ID AND Orders.ID = 12345;
Copy after login

The ON clause dictates that only rows where OrderLines.OrderID matches Orders.ID and Orders.ID equals 12345 will be included in the join. This filtering happens during the join process.

Key Semantic Distinction

Although WHERE and ON might yield similar results with INNER JOINs, their semantic roles are distinct. WHERE filters the final joined dataset, while ON determines which rows are included in the join operation.

The above is the detailed content of SQL JOIN: WHERE vs. ON: What's the Key Difference in Filtering Joined Data?. For more information, please follow other related articles on the PHP Chinese website!

Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot Article

R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)
2 weeks ago By 尊渡假赌尊渡假赌尊渡假赌
Repo: How To Revive Teammates
4 weeks ago By 尊渡假赌尊渡假赌尊渡假赌
Hello Kitty Island Adventure: How To Get Giant Seeds
3 weeks ago By 尊渡假赌尊渡假赌尊渡假赌

Hot Article

R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)
2 weeks ago By 尊渡假赌尊渡假赌尊渡假赌
Repo: How To Revive Teammates
4 weeks ago By 尊渡假赌尊渡假赌尊渡假赌
Hello Kitty Island Adventure: How To Get Giant Seeds
3 weeks ago By 尊渡假赌尊渡假赌尊渡假赌

Hot Article Tags

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

Reduce the use of MySQL memory in Docker Reduce the use of MySQL memory in Docker Mar 04, 2025 pm 03:52 PM

Reduce the use of MySQL memory in Docker

How do you alter a table in MySQL using the ALTER TABLE statement? How do you alter a table in MySQL using the ALTER TABLE statement? Mar 19, 2025 pm 03:51 PM

How do you alter a table in MySQL using the ALTER TABLE statement?

How to solve the problem of mysql cannot open shared library How to solve the problem of mysql cannot open shared library Mar 04, 2025 pm 04:01 PM

How to solve the problem of mysql cannot open shared library

Run MySQl in Linux (with/without podman container with phpmyadmin) Run MySQl in Linux (with/without podman container with phpmyadmin) Mar 04, 2025 pm 03:54 PM

Run MySQl in Linux (with/without podman container with phpmyadmin)

What is SQLite? Comprehensive overview What is SQLite? Comprehensive overview Mar 04, 2025 pm 03:55 PM

What is SQLite? Comprehensive overview

Running multiple MySQL versions on MacOS: A step-by-step guide Running multiple MySQL versions on MacOS: A step-by-step guide Mar 04, 2025 pm 03:49 PM

Running multiple MySQL versions on MacOS: A step-by-step guide

What are some popular MySQL GUI tools (e.g., MySQL Workbench, phpMyAdmin)? What are some popular MySQL GUI tools (e.g., MySQL Workbench, phpMyAdmin)? Mar 21, 2025 pm 06:28 PM

What are some popular MySQL GUI tools (e.g., MySQL Workbench, phpMyAdmin)?

How do I configure SSL/TLS encryption for MySQL connections? How do I configure SSL/TLS encryption for MySQL connections? Mar 18, 2025 pm 12:01 PM

How do I configure SSL/TLS encryption for MySQL connections?

See all articles