How to use ‘awk’ to print columns from a text file (in any order)

One of my favorite ways to use the Unix awk command is to print columns of information from text files, including printing columns in a different order than they are in in the text file. Here are some examples of how awk works in this use case.

How to find all MySQL database tables that have specific column names

MySQL FAQ: How can I find all MySQL database tables that have specific column names?

I found the solution on this SO page. Here’s my take on it.

First, assuming that you want to copy and paste those column names after you get them, I recommend starting the MySQL command line client like this:

How to create a URL column in a Sencha ExtJS grid panel

I don’t know if this is the best way to do this, but if you want a column in a Sencha ExtJS grid to display a URL field that the user can click, I can confirm that this code works:

A Sencha ExtJS grid/date example with sample static data

It’s often hard to find good Sencha ExtJS examples, but I ran across this one last night. It shows how to use a date column in a Sencha grid. I’ve highlighted the date column information in the source code below:

Perl CSV file column extraction

Perl CSV column data extraction FAQ: Can you share an example of how to extract one or more columns from a Perl CSV file or other similarly-formatted flat text file?

Perl is a terrific language for text processing, but several readers have written wondering about how to extract columns of data from text files with Perl. For instance, when you have a text database that looks like this:

Ruby - How to sort an array of objects by one field

Sorting an array of objects by one column in the object (class) is pretty simple with Ruby. Here's a quick demo of how I just did this when working on sorting the rows in a CSV file in a simple Ruby script.

Define the class

Step 1 in this is defining my class. So, here's the definition of my Ruby Person class:

How to perform a SQL query for fields that are null (or not null)

For some reason I can never remember how to search for database table fields that are either NULL or NOT NULL. I always try to use the = operator or something else.

So, for myself, here’s an example of how to perform a SQL query and find all records where a field in a database table is NULL:


And here’s how to perform a SQL query showing all records in a database table where a column is NOT NULL:

A MySQL database table index example

MySQL FAQ: How do I create a MySQL database table index?

Here's an example of how to create an index on a MySQL database table. In this particular example my table uses the MySQL InnoDB database engine, but that doesn't matter too much -- it just happens to be a MySQL database engine that supports foreign key relationships.

To get started, here's the SQL definition of a MySQL table I've named ftp_files:

How to create a JComboBox in a JTable column with JFormDesigner

In a heavy day of JFormDesigner use, I just learned how to create a JComboBox in a column in a JTable, using only JFormDesigner.

First, create your JTable in JFormDesigner. I'll skip the details here, hoping that process is easy enough. Then, click the ellipsis button for the model property in the Properties list. This brings up the JTable model editor.