Join Bill Weinman for an in-depth discussion in this video Using multiple related tables, part of SQL Essential Training.
…In practical terms, it's very common to…have tables with many to many relationships.…For example, a single customer may buy many items…and a single item may be purchased by many customers.…This is often implemented with adjuction table.…Here's a simple and practical example.…Be using the test.db database for this example.…And lets start by just looking at the table structures in the test database.…So here's the three tables in this database.…There's customers, there's items, and there's sales.…
And you notice each of these tables has an ID column.…The ID column identifies a specific row in each table.…The sale table performs the role of a junction table.…Its item ID and customer ID columns allow the…other two tables to have a many to many relationship.…That is a customer may be related to many…items and an item may be related to many customers.…A junction table is a common way to accomplish this.…Junction tables are common in the database world, sometimes…linking many tables, and sometimes performing many separate roles.…
- Understanding SQL terminology and syntax
- Creating new tables and records
- Inserting and updating data
- Writing basic SQL queries
- Sorting and filtering
- Accessing related tables with JOIN
- Working with strings
- Finding the numeric type of a value
- Using aggregate functions and transactions
- Updating a table with triggers
- Creating views
Skill Level Beginner
Q: For Mac OS X: When I try to start the Apache Web Server from the XAMPP control panel, it doesn't start, and when I open "localhost" in my web browser, I see a white screen that says "It Works!" instead of the XAMPP page.
sudo apachectl stop
Q: I'm on a Mac, and I get an error in SID that says "attempt to write a read only database." How can I fix this?
A: This usually means that the database folder does not have sufficient permissions for writing by the web user. This can happen if you create the SQL folder new, rather than copying it from the Exercise Files. Here's how to fix this:
- Open a Finder window and Navigate to /Applications/XAMPP/htdocs/SQL
- Control-click on the SQL folder and select "Get Info" from the context menu.
- Under "Sharing and Permissions" (you may need to open the disclosure triangle), in the "everyone" row, select "Read & Write."Then you can close the Info window.
- Now repeat the process for the three *.db files inside the folder.
1. SQL Quick Start
Understanding joins2m 23s
Dates and times1m 59s
10. Subselects and Views
11. A Simple CRUD Application
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