Jump to content



Highest Reputation Content


#6644 Just Started This Book Today!

Posted by rob on 26 March 2012 - 10:53 AM

It does affect something it affects the source code layout, which is the whole point of using it, to make source code more readable.
  • 4


#3208 Some Tips When It Comes To Mysql Queries

Posted by Antonio Conte on 20 August 2011 - 11:19 PM

1. Always name your tables the same way:
There are best practice rules for naming tables. They should always be lowercase, split by underscore ( _ ) and named in plural. If you need to build tables for several purposes, (forums, shops, fruits) prefix them so the appear next to each other.

Examples:
forums_users
forums_posts
shops_products
shops_prices
shops_availability

2. Use normalization rules(!!!) when creating a structure for tables
Larry explains the different forms of normalization very good in this book. Read it thoroughly, UNDERSTAND it, and plan your tables well. The rules are really not that hard to understand, and will allow you to cross-reference tables in an easy way later on. It will make you understand how the data you are using are working. It will make your systems a lot easier to build on and to introduce new features. I promise you, THIS is how you become a wizard when it comes to working with data in several tables.

3. Use white space(!) and use UPPERCASE for mysql functions (See tip #4!)
When your queries becomes increasingly more complex, you should really follow these tips. To demonstrate, I will give you two versions of the exact same code:

CREATE VIEW view_goals_per_game AS

SELECT league.season AS season,
league.id AS league_id,
league.name AS league_name,
goals.match_id AS match_id,
clubs1.name AS hometeam,
clubs2.name AS awayteam,
players.id AS player_id,
CONCAT( players.fornavn, ' ', players.etternavn ) AS player_name,
goals.goal_time AS goal_time,
games.kickoff_time AS kickoff_time

FROM abc_players_goals AS goals

INNER JOIN cnk_soccer_games AS games ON ( goals.match_id = games.id )
INNER JOIN cnk_soccer_clubs AS clubs1 ON ( games.club1_id = clubs1.id )
INNER JOIN cnk_soccer_clubs AS clubs2 ON ( games.club2_id = clubs2.id )
INNER JOIN abc_players AS players ON ( goals.player_id = players.id )
INNER JOIN cnk_soccer_league AS league ON ( league.id = games.league_id )

LIMIT 0, 1000

create view view_goals_per_game as select league.season as season, league.id as league_id, league.name as league_name, goals.match_id as match_id, clubs1.name as hometeam, clubs2.name as awayteam, players.id as player_id, concat( players.fornavn, ' ', players.etternavn ) as player_name, goals.goal_time, games.kickoff_time from abc_players_goals as goals inner join cnk_soccer_games as games on ( goals.match_id = games.id ) inner join cnk_soccer_clubs as clubs1 on ( games.club1_id = clubs1.id ) inner join cnk_soccer_clubs as clubs2 on ( games.club2_id = clubs2.id ) inner join abc_players as players on ( goals.player_id = players.id ) inner join cnk_soccer_league as league on ( league.id = games.league_id ) limit 0 , 1000

Whick one would you like to maintain? :blink:

4: Save your queries in a text editor

Yes! It sound idiotic, right? It's not. Think of this happening: You accidentally delete, modify or overwrite a query you've used a lot of time on. It will save you a lot of time, tears and the life of a few keyboards! This is also leading up tip number 5.

5. Use views instead of customizing your dataset in PHP(!)
This is a real life-saver. Think of it as including ONE central PHP file instead on chancing 10 documents every time you make a change. The views should be written to display AS MUCH information as possible. Try to think of every scenario you may want to use the data. Views are, with a few exceptions, for displaying data; hence it's name.

NOTE: After the creation of a view, you CANNOT modify it. This is why you should follow step 4.

- Views are really easy to create:
[u][i]CREATE VIEW the_name_of_the_view AS[/i][/u]
SELECT *
FROM table1

The query used in tip #3 is a view. It would allow you to sort by a specific league, match_id, player_id or by kickoff_time. The view is used to display statistic about the goal scorer in a football match. (soccer for americans) The table for saving goal statistic has three rows(!). Match_id, player_id and goal_time. This is good data normalization, and minimizes redundancy and make for consistent data. That means the table players_goals need to be linked with other tables that holds data about the specific match and the specific player. This is the reason for create a view.

Don't see the point of this?
There really is one - I promise! By writing a view that is general and display a lot of data, I can write SIMPLE queries to get different results:

1. Last five goal scorers with name of both teams, player name and goal time
SELECT hometeam, awayteam, player_name, goal_time
FROM view_goals_per_game 
ORDER BY kickoff_time DESC

2. Display players with most goals in descending order
SELECT player_name, COUNT(*) as goals
FROM view_goals_per_game
GROUP BY player_id
ORDER BY goals DESC

3. Display all goals by a specific player
 SELECT hometeam, awayteam, player_name, goal_time
FROM view_goals_per_game
WHERE player_id = 10
ORDER BY kickoff_time DESC

4. Find all goals in a specific match
SELECT hometeam, awayteam, player_name, goal_time
FROM view_goals_per_game
WHERE match_id = 837

Does it start to make some sense? Instead of repeating and modifying the same hard-to-grasp code over and over again (see tip #3), use a view to make your life simpler. :)

Hope this has helped someone. I have been thinking about writing a lot of different tips when it comes to MySQL. I've been thinking about writing a guide to joins for example. I really don't know if this interests someone or not.

Hoping others will also share tips and experiences when it comes to MySQL. :)
  • 4


#14402 Really Disturbing

Posted by margaux on 1 May 2013 - 4:56 PM

Hey xto, I'm going to try to say this in the nicest way possible -  You're in danger of trying people's patience not because you ask questions, we like questions, but because you ask questions in a way that doesn't provide the information needed to try to answer them.

 

1. please read the forum guidelines - Look for the little grey text bottom right of most pages, labelled Guidelines

2. please post only RELEVANT code and error messages within code tags. We don't need to see the entire output from your error message. It's actually distracting. Use code tags which are on the edit bar and they look like <>

3. post the relevant CODE, you keep posting the error message but not any code.

4. You should start a new thread for each new question. One reason for doing so is that other people with the same question can search and find your thread. If your question is part of another thread, it won't be found and won't help others.

5. You're asking questions that you should be able to solve 1 because the level of  experience for this book expects you know some basic debugging strategies and 2. with a little bit of online searching you would get some pointers as to where to look for the cause of your error.

 

I really shouldn't answer your question given the above but ...

 

somewhere in your code you are referencing an array value using 'sale_price' as the index, which doesn't exist. I'm going to hazard a guess that you have a line that includes $row['sale_price']. From the error dump you posted, you will see there is no index 'sale_price' but there is one named 'price'. Given what info you've provided that's all I can help with. If this doesn't help solve the problem, start a new thread and post the code that is causing the error :)


  • 4


#8626 Chapter 3 - Returning Values From A Function

Posted by HartleySan on 12 July 2012 - 5:54 PM

When you call the calculate_trip_cost function (as is the case on line 48 in the script), the three arguments specified within the parentheses and separated by commas are mapped to the three parameters (also sometimes called arguments; it doesn't really matter) within the parentheses in the function definition header on line 24.

In the code in the book, this corresponds to the value in $_POST['distance'] being mapped to the parameter $miles, the value in $_POST['efficiency'] being mapped to $mpg, and the value in $_POST['gallon_price'] being mapped to $ppg. (And when I say mapped, I simply mean that the values in the arguments in the function call are copied to the corresponding parameters in the function definition header.) By doing this, you can use values that were set or established outside of the function within the function, which relates to the variable scope discussion.

As another example, if I wrote the function call calculate_trip_cost(1, 2, 3), then 1 would be set for $miles, 2 would be set for $mpg, and 3 would be set for $ppg.

As for how the $_POST array contains values in the first place, that relates to other discussions earlier in the book. Basically though, when you submit an HTML form (with the post method), PHP is designed to automatically store all values within the form into the $_POST superglobal associative array (just to throw some other vocab out there for you).

Does all that make sense? Please let me know if it doesn't.
  • 3


#8470 Normalization

Posted by margaux on 2 July 2012 - 6:28 PM

Look up JOINs as that will achieve what you're after. However, you will need values in the foreign keys columns, otherwise how will you cross-reference the records in the corresponding tables.
  • 3


#20294 Php/mysql Error Message?

Posted by Emilie on 19 August 2014 - 7:53 AM

Hello,

 

MySQL doesn't 'know' the variables you created with PHP. In order to test your query, you need to replace the variables with their values.

 

I hope this helps,

 

Emilie


  • 3


#20055 I'm Having Trouble With Sorting Query Results In Chapter 5... Plz Help!

Posted by Emilie on 30 July 2014 - 1:07 PM

Hello,

 

What is "wrong", according to you?

 

The registration date is the same for all users because you entered all of them at one go into the database, and therefore the timestamp corresponding to NOW() is the same for everyone. Because of that, ordering the results by registration_date DESC has no real meaning.

 

I hope this helps,

 

Emilie


  • 3


#14154 Multiple Mysql_Fetch_Array That Drives Me Nuts

Posted by HartleySan on 18 April 2013 - 3:12 PM

Hmmm... I'm not entirely sure what you're going for, but I'm definitely seeing some serious inefficiencies. While I don't know the sizes of your tables (i.e., how many records each one contains), you seem to be grabbing everything from the purchases table, and within that while loop, you are then grabbing everything from the other two tables where a certain value equals a certain value in the purchases table.
 
Also, a lot of the math you're doing (for example, adding up values for the amount of a given order) and formatting of the date can be done on the DB side, which can further speed things up.
In general, I think your goal should be to format all your data exactly the way you want to print it out to the screen by using one query. That may not be possible, and I'm not entirely sure what you want, but I'm thinking that we *may* be able to get everything you want in one query. I will attempt to do so below, but I can't guarantee that it'll work.
 
To start with, I'm trying really hard to figure out what exactly you're going for, but it's a bit abstract with the variables you're using. I'm not sure if you're using those variables on purpose to disguise your code for this thread, or if you're really using those variables in your code, but either way, I would definitely recommend using more logical variable names.
 
Anyway, here's my interpretation of your code:
You're printing out a table of purchase orders. The first column is the row number (which you do not seem to be properly incrementing within the outer while loop). The second column is the ID of a purchase order that a customer has made. The third column is the name of the customer (and it looks like you're storing their first and last name in one column in the customers table, which I would recommend against). The fourth column is the date and time of the purchase. The fifth column is the total amount of the purchase order formatted in dollars and cents. Lastly, I'm not sure what the last two columns are, but they aren't coming from DB data, so I'll ignore those for now.
 
Assuming my interpretation above is correct, I think you need to do an inner join across three tables with the purchases table being the main table. Also, I think you need to group your purchases together by the purchase ID, so that you can use an aggregate function to add up the price of the individual items within each specific order.
Does that make sense?
 
Anyway, here's the query that I'm *thinking* will work (but I can't guarantee that it does or that it's what you want):
SELECT c.cust_id, c.name AS cust_name, p.po_id AS order_num, p.cust_id, DATE_FORMAT(p.timestamp, '%m %d, %Y') AS date, o.po_id, SUM(o.delivered * o.srp) AS amount
FROM customers AS c, purchases AS p, po_content AS o
WHERE c.cust_id = p.cust_id AND p.po_id = o.po_id
GROUP BY o.po_id
ORDER BY p.timestamp ASC
LIMIT $start $display;
 
A few notes about the query:
1) For your query, a join is essential. Specifically, two inner joins on the purchases table is what you need. Joins are tricky at first, but they're essential for most DBs, so I'd recommend studying up on them.
 
2) Only select the columns you need. Using SELECT * for three separate queries is getting you a lot of data you don't need, and is very inefficient.
 
3) Use aliases (e.g., "AS c", "AS p", etc.) on the tables to make typing out the query shorter and easier. Also, aliases are essential for being able to easily reference the results of aggregate functions, formatted, dates, etc.
 
4) Format the timestamp on the SQL side using the DATE_FORMAT function. It's faster and easier. Also, give the formatted date an alias to make it easier to access on the PHP side. Here's more info on the DATE_FORMAT function:
 
5) I'd calculate the total amount of each order on the SQL side. To do so, you need to use the SUM aggregate function, and also use the GROUP BY clause to group your results together by order number so that you are adding up the correct grouping of items. Also, I'd assign an alias to the result of the SUM function.
 
6) The "ASC" part of the query is not necessary, since that's the default ordering. I left it anyway to avoid any further confusion.
 
7) I used "o" as the alias of the po_content table, as it seems like a table of orders to me.
 
That will hopefully handle the query side of things.
Unfortunately, I think there are some other issues with your code as well:
1) You're not incrementing $rownum in the while loop.
 
2) You're assigning your $bgcolor value to the entire table, not individual table rows. Also, I'm pretty sure the resulting HTML will be syntactically invalid and not work.
 
3) You're creating a new table each time through the while loop.
 
4) You're putting a div within a td for the total, which I wouldn't do.
 
Point being, without sounding too harsh, I think your code has some serious issues and needs some re-working. I get the feeling that you might be getting a bit too ambitious about your personal project without first understanding all the basics you need.
I don't mean to say that you shouldn't be ambitious, but I think you should probably go back to the book for a bit and bone up on queries with joins, HTML and PHP syntax, as well as think more about the logic of your while loop and the type of HTML that it is creating.
 
Anyway, below, I'm going to present the PHP I would use for your situation. Again, please keep in mind that I'm doing my best to piece together exactly what you want (and I'm not entirely sure), so I could be way off on this.
// I'm assuming that $agent and $encoder are already defined above.
 
$row_num = 1;
 
$total = 0;
 
$bg_color = '#FFF';
 
$q = "SELECT c.cust_id, c.name AS cust_name, p.po_id AS order_num, p.cust_id, DATE_FORMAT(p.timestamp, '%m %d, %Y') AS date, o.po_id, SUM(o.delivered * o.srp) AS amount FROM customers AS c, purchases AS p, po_content AS o WHERE c.cust_id = p.cust_id AND p.po_id = o.po_id GROUP BY o.po_id ORDER BY p.timestamp ASC LIMIT $start $display;";
// I'm assuming that $start and $display are already defined above.
 
$r = mysqli_query($dbc, $r);
// I am assuming that $dbc is already defined above. You also seem to have omitted this argument in your code.
 
echo '<table class="order_details">';
// I'd use CSS to properly format the table instead of the inline attributes you're using.
// As such, I have assigned a class to the table for that exact reason.
// Also, your table doesn't have any headers, but you may want to add them along with thead, th, tbody, and tfoot tags.
 
while ($row = mysqli_fetch_array($r, MYSQLI_ASSOC)) {
  
  echo '<tr style="background-color: ' . $bg_color . ';">
  
  <td>' . $row_num . '</td>
  
  <td>' . $row['order_num'] . '</td>
  
  <td>' . $row['cust_name'] . '</td>
  
  <td>' . $row['date'] . '</td>
  
  <td>' . number_format($row['amount'], 2) . '</td>
  
  <td>' . $agent . '</td>
  
  <td>' . $encoder . '</td>
  
  </tr>';
  
  $row_num++; // Don't forget to increment this.
  
  $total += $row['amount']; // This is the summation of the unformatted amounts, which could cause issues.
  
  $bg_color = ($row_num % 2 === 0) ? '#F3F3F3' : '#FFF'; // Ternary operation for brevity
  
}
 
echo '<tr style="background-color: ' . $bg_color . ';">
 
<td colspan="4" class="total_row">Total</td>
 
<td>' . number_format($total, 2) . '</td>
 
</tr>';
// Formatted to line up with the amount column.
// Also, note that I handled the total the same way you did, but if you calculate the total on the
// unformatted amount values, then you may get a discrepancy in which the amounts don't add up to the total.
// Also, again, I'd use CSS (not inline HTML) to align "Total" to the right.
// Lastly, you may want to put the total in a tfoot element.
 
Well, I think that's about it.
After all this writing, I really hope that I got close to what you wanted, and that this post is of some use.
Please let me know.
Thanks.

  • 3


#13394 Pls Help Need Urgent Help. The .Inc Extension. Chapter 11

Posted by margaux on 11 March 2013 - 4:45 AM

It's difficult to debug when the code is presented in this way. Please would you use code tags.

 

At first look, no error immediately jumps out. Which line is line 46? Look at that line and the few lines before it.

 

Probably not causing this error but it looks like you may have a typo on the tablename in the SELECT statement - users instead of usera?


  • 3


#11339 Ch. 11 Using Unlink() With A Reset Button Possible?

Posted by Antonio Conte on 27 November 2012 - 10:43 PM

This can absolutely be done via GET. What you would do is using IDs as the get value. Save the filenames to an array on the form ID => "name". You then build links the same way, but with ?remove=$ID. You cast $_GET['id'] to an integer, find the filename in array by using the ID, build a full path where you add the filename, then use unlink() to delete the file.

An easy way to do this would be something like:


$handle = ""; // open file

$file_array = array(); // The file names

while ( ($file = readdir($handle)) !== false )
{
    if ($entry != "." && $entry != "..")
    {
	   $file_array[] = $file;
    } // Read files to array
}

// Simple delete
if ( ! empty($_GET) )
{
   
    $upload_dir = "uploadsDirectoryHere/"; // Upload dir
    $file_id = (int) $_GET['delete']; // File_array ID

    // Make sure file is found
    if ( array_key_exists($file_id, $file_array) )
    {
		 $delete_file = $upload_dir . $file_array[$file_id];

		 // Make sure file exists
		 if ( file_exists($delete_file) )
		 {
			  unset(file_array[$file_id]); // Remove from file array
			  unlink($delete_file); // Actually delete file here
		 }
    }

// Print out file names and links for deleting them
foreach ( $file_array as $id => $filename )
{
    echo $filename . '<a href="page.php?delete='.$id.'">Delete file</a>;
}

Not tested, but that should be the basic idea. Sorry about errors/etc. Beginning to get tired here.
  • 3


#10870 Page 303

Posted by margaux on 2 November 2012 - 4:42 AM

I would have thought the error in the query was due to the ORDER BY clause. In your query you create an alias for the date_registration by do not use it in the ORDER BY clause. It should be
$q = "SELECT last_name, first_name,
➝ DATE_FORMAT(registration_date, '%M
➝ %d, %Y') AS dr, user_id FROM users
➝ ORDER BY dr ASC
➝ LIMIT $start, $display";

Its definitely worth spending time on the debugging chapter - you will save yourself loads of time in the future and learn a few tricks. One quick trick is to insert something like
print_r($r)
in your code which will give you full information about your query in a more readable format.
  • 3


#10752 Chapter 8: Page 290 Referencing The Event Section

Posted by Antonio Conte on 29 October 2012 - 7:02 PM

You'll see this often in programming if the function uses well known functionality. It's much clearer with parameter hinting as you get the object type to. It's also more common if classes implement well-known interfaces to get functionality. Below is an example from Java that allows to to get input from a mouse. These types of interfaces can include 15-20 methods, so you would spare a lot of code by just using Event e.

class MouseInput implements MouseListener
{
   public void mouseClicked( MouseEvent e ) { }
   public void mouseEntered( MouseEvent e ) { }
   public void mouseExited( MouseEvent e ) { }
   public void mousePressed( MouseEvent e ) { }
   public void mouseReleased( MouseEvent e ) { }
}

AnyEvent e is pretty much standard naming for events, as is Graphics g, Comparator cmp or Iterator itr. These of course differ slightly in difference languages, etc, but are pretty general well known names for the functionality they provide. These names are not "standards" by any stretch of the imagination, though, so feel free to use what you like.
  • 3


#10740 Paypal Integration Confusion

Posted by MrJames on 29 October 2012 - 7:14 AM

Hi,

Try the following as an example:

<input type="hidden" name="amount" value=" ' . $productPrice . ' ">

Regards
  • 3


#12215 When Js Isn'T Available.

Posted by HartleySan on 8 January 2013 - 6:24 PM

Unfortunately, that's the nature of the beast. With JS disabled, you lose a lot of functionality, and certainly, that's one if the downsides of relying on JS libraries to do all the work for you.

Obviously, you'd most likely want the non-JS version of your site to mirror the JS version as much as possible, but that's not always possible/practical. With that said, I think Larry says in one of his books somewhere, as long as the non-JS site works and gets the user the information necessary, that's good enough (even if the site looks/behaves like crap). I more or less agree with this, but obviously, if given the time, making a non-JS version of your site that is similar in appearance and functionality never hurts.

Here's my main COA when designing a site to have both a non-JS and JS version:

1) Plan, plan, plan! In regards to the above, this means trying to minimize JS as much as possible while still giving a good experience. By minimizing the JS used, the two sites will be more similar and it'll be less work to get both working correctly.
Unfortunately, if you're locked into something like Twitter bootstrap, then you might have your work cut out for you in this regard. This is one of the main things I don't like about a lot of JS libraries these days: they use JS for a lot of things you don't need JS for; nowadays, you can do a lot with HTML and CSS alone.

2) Use noscript tags for content that is required as a replacement for JS-generated content when JS is disabled. For example, you might make a new, second menu within noscript tags to handle navigation when your Twitter bootstrap menu is busted because JS is disabled.

3) For content that requires JS, either generate the markup for it using JS, or use CSS to hide the content by default, and then use JS to display it when the page first loads. If you don't do one or the other, then you will get JS-dependent content appearing on the screen, which is useless and confusing to users who have JS disabled (ala your Twitter menu).

4) With all the above in mind, develop the entire site first without using any JS. This will serve as a solid base. After that, add JS functionality as needed, keeping all the above in mind. Because this may be time-consuming, you may want to consider launching with the non-JS version only (since that should be enough to do whatever on your site), and then adding JS functionality here and there post-launch.

And that's basically it. Obviously, depending on the scope/size of your site, this may add considerable time to development, but that's the price you pay if you want a decent non-JS site. I think a log of people these days don't find it worth the effort to do all of the above though (so they don't).

And keep in mind that there are other things to consider these days as well. For example, "mobile first", which is a good guiding principle and strongly emphasizes loading content non-essential for the mobile version using JS. These sorts of considerations may very well conflict with designing a good non-JS site, so please keep that in mind.

Well, I've blabbered on long enough, and I probably mentioned a bunch of stuff you already knew, but there ya go.

- The other Jonathan (with a slightly different spelling)
  • 3