Join Bill Weinman for an in-depth discussion in this video Creating a simple subselect, part of SQL Essential Training.
…Subselects are effectively nested select statements.…In SQL the result of the select statement is effectively a table.…It may or may not be temporarily written to fix storage,…but it can always be used as you would use a table.…Because of this, a select statement may be…used as a data source in another select statement.…This usage is a called a subselect.…We'll be using the world.db for this lesson.…And I'm going to go ahead and copy and paste…some code here from the exercise file for chapter 10.…
And I'll paste it in here in our sql box.…We're creating a temporary table called T.…It has two columns, both of them text columns.…And we're inserting some rows into it and then selecting from it.…So you can see what it is.…And there's our two columns.…Each of these columns actually has two pieces of data…in it, which we're going to extract with a select statement.…The first column has some state code names,…some two letter state abbreviations from the United States,…and the second column has two letter country code…
- 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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