database

MySQL syntax examples - create table, primary key, foreign key

Just a quick note here today that if you need some example MySQL database tables, you can use these. I created them for some experiments I ran last night. They show the MySQL create table, primary key, and foreign key syntax:

By Alvin Alexander on May 9, 2013

Scala - calling foreach on a Seq to populate sample data

I just saw the following Scala source code in a Play Framework 2 sample application, and it struck me as a nice example of how to call the foreach method on a Seq to populate some sample data:

By Alvin Alexander on April 25, 2013

MySQL show status - show open database connections

MySQL "show status" FAQ: Can you demonstrate how to use the MySQL show status command to show MySQL variables and MySQL status information, such as the number of open MySQL connections?

I don't have a whole lot of time today to give this a detailed discussion, but here is a quick look at some MySQL work that I did recently to show MySQL open database connections.

By Alvin Alexander on April 25, 2013

A MySQL 'create table' syntax example

I used to use MySQL every day for years, but over the last two years I haven't used it much. Today I needed to create a MySQL database table, and had to wonder for a few moments what the MySQL CREATE TABLE syntax was. Fortunately I have plenty of examples out here.

Here's a quick example of a MySQL "users" table:

By Alvin Alexander on October 8, 2012

Managing MongoDB connections with the Scala Casbah database driver

UPDATE: November 14, 2012. This article describes problems I had when attempting to use the Scala Casbah driver for the MongoDB database. In the end, it turned out I was doing something wrong. However, because this article shows how to troubleshoot MongoDB and Casbah database connection problems, it seems like a good idea to leave it here. If you want to see the correct way to use Casbah with MongoDB, I created this Github project, which shows the correct approach.

By Alvin Alexander on April 25, 2013

Scala cookbook recipes

Wow, I began by writing a few Scala programming tutorials just because I like the language, and as I look here a couple of months later I now have more than sixty tutorials. As a result, I thought I'd start organizing them here in the form a Scala Programming Cookbook.

Here's my current collection of Scala FAQs and recipes, in a "cookbook" format.

By Alvin Alexander on May 17, 2013

Android - SQLiteOpenHelper failing to call onCreate (not creating database)

Android/SQLite FAQ: I've created an instance of a SQLiteOpenHelper object, but the onCreate method isn't getting called, what's wrong? (onCreate is not getting called, and my database tables are not being created.)

By Alvin Alexander on March 7, 2012

SQLite - default a datetime field to the current time (now)

SQLite FAQ: How do I default a SQLite datetime field to the current date and time? (i.e., how do I default it to now?)

Just use the SQLite current_timestamp function, like this:

last_updated datetime default current_timestamp

In a more complete create table example I just used on an Android project, this looks like this:

By Alvin Alexander on March 7, 2012

SQLite - Create a unique constraint on multiple columns (fields)

SQLite FAQ - How do I create a UNIQUE constraint on multiple fields in a SQLite database table?

Just specify the unique constraint in your create table declaration, as shown here:

By Alvin Alexander on March 7, 2012

SQLite - How to list the tables in a SQLite database

SQLite FAQ: How do I list the tables in a SQLite database?

To generate a SQLite tables list, just log into your SQLite database with the sqlite3 command, and then issue the "tables" dot command:

By Alvin Alexander on March 7, 2012
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