Join Bill Weinman for an in-depth discussion in this video Finding the length of a string, part of SQL Essential Training (2014).
While the SQL standard does not include a function for finding the length of a string, most modern database systems do include one and it's usually called length. For this example, we'll be using the world.db database. And finding the length of the string looks like this. Here, I'll be getting the length of the literal string, with the word string in it, which is six letters long. So when I press go, I get a result that says six. Of course, this is much more useful as part of a query, so let's create a query here.
So there's a query that will list the name, the length of the name from the city table and ordered by length descending, and name within the ordering of the length. So when I press go, you see we have a list of the cities, ordered by their length descending. And when there are more than one with the same length, the cities are in alphabetical order. While length is not a standard SQL function, it is supported in most database systems. The name is usually length but you should check your documentation for details and variance.
- 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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