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Dynamic Column Names

Posted on 2013-12-03
Medium Priority
Last Modified: 2013-12-17
I'm building a PHP script that will run monthly, to gather data from different tables and bring it into a new table.

As it stands right now, I am dropping the tables monthly, and re-creating them in this script.  The column names consist of the month name and year, and therefore will change monthly.

For example, the table I'm working in right now has a column for november12, december12, january12, all the way through december13.

I need to extract the data from the columns in order to calculate averages, and more importantly, display the data on the page.

My question is how to structure my SELECT query based on these dynamic column names, and then how to put them into variables to display on the page in my WHILE loop?

Here is how I am naming the columns.

#Get Months between last month and 12 months ago
function getAllMonths($date1, $date2)
	$time1 = strtotime($date1);
	$time2 = strtotime($date2);
	$my = date('mY', $time2);
	$months = array(date('Y-m', $time1));
	while($time1 < $time2) 
		$time1 = strtotime(date('Y-m-d', $time1).' +1 month');
		if(date('mY', $time1) != $my && ($time1 < $time2))
		$months[] = date('Y-m', $time1);
	$months[] = date('Y-m', $time2);
	$months = array_unique($months);
	return $months;

#Define Months to use
$thisMonth = date("Y-m", strtotime($today));
$yearAgo = date("Y-m", strtotime("-1 year", strtotime($thisMonth)));
$allMonths = getAllMonths($yearAgo, $thisMonth);

#Build the quality calls table!
$crt = "CREATE TABLE IF NOT EXISTS `repanalysis_qualitycalls`
			`id` int(20) NOT NULL auto_increment,
			`respid` int(6) NOT NULL,";
foreach($allMonths AS $monthRange)
	$monthNames = date("Fy", strtotime($monthRange));
	$crt .= '`'.$monthNames.'` decimal(7,2) default 0,';
$crt .= "`averageqc` decimal (15,2),
			`avgtogoal` decimal (15,5),
			`qc_regionalrank` int(10),
			`qc_overallrank` int(10),
			 PRIMARY KEY  (`id`),
			 KEY `respid` (`respid`)
$result = mysql_query($crt) or die("Cannot create quality calls table: " . mysql_error());

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I tried doing a select * but I'm not sure how to get the column names out of that query:

	//Extract Quality Calls for Calculations.
	$getQC = mysql_query("SELECT * FROM repanalysis_qualitycalls") or die("Cannot pull quality calls: " . mysql_error());

	if(mysql_num_rows($getQC) > 0)
		while($row = mysql_fetch_assoc($getQC))
			$repId = $row['respid'];

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Question by:t3chguy
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LVL 35

Expert Comment

ID: 39693468
You can either run a DESCRIBE <table> query to get the table structure, or as long as you have a record, you can just look at the keys of any record that is returned with mysql_fetch_assoc().

By the way, mysql_ functions are deprecated, so you may want to consider moving to the newer mysqli functions.
LVL 35

Expert Comment

ID: 39693469

Author Comment

ID: 39693482
How can I use the key from the mysql_fetch_assoc?
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LVL 35

Accepted Solution

gr8gonzo earned 2000 total points
ID: 39693541
Use array_keys:

if(mysql_num_rows($getQC) > 0)
		while($row = mysql_fetch_assoc($getQC))
			$repId = $row['respid'];
                        $columns = array_keys($row); // <<<<<<<<<<<<<<<<<<<<<<

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LVL 27

Expert Comment

by:Cornelia Yoder
ID: 39693707
Try mysql_list_fields() to get field names
(deprecated but still works beautifully)

 or mysql_query() to issue an SQL SHOW COLUMNS FROM table [LIKE 'name']
LVL 111

Expert Comment

by:Ray Paseur
ID: 39693720
You probably want to define DATE columns as data type DATE.  Then you can use the standard ways of getting the data.  There is a little more about how to handle DATE and DATETIME information in this article.

That said, I would expect that it might make sense to have the date values in a single column in each of the rows instead of in columns for each date.  One example of why that might be an advantageous design would emerge if the boss comes in and says, "Give me the last two years data."  If the dates are in one column you just change the query.  If the dates are in columns by month, you have to rewrite your script.

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