In some languages (ColdFusion comes to mind), you can run a query on the result set from a previous query. Is it possible to do something like that in php (with MySQL as the database)?
I sort of want to do:
$rs1 = do_query( "SELECT * FROM animals WHERE type = 'fish'" );
$rs2 = do_query( "SELECT * FROM rs1 WHERE name = 'trout'" );
There is no MySQL function like this for PHP, however there is a more advanced substitute for it.
Edit: For those of you who don't know what a query of queries is, it's exactly this and there's a purpose some people do it like this. Using an AND operator is ****NOT**** the same thing! If I want results where username='animuson' for one part of my script and then want all the results out of that query where status='1', it is not logical for me to run another query using an AND operator, it is much more logical to loop through the previous results in PHP. Stop upvoting things without reading the comments on why they weren't upvoted in the first place, that's just lazy. If you don't have a clue what's being talked about, you shouldn't be upvoting or downvoting in the first place.
Well, you may want to do this without touching the db:
while($t = mysql_fetch_array($rs1)){
if($t[name] == 'trout'){
echo 'This is the one we\'re looking for!';
break;
}
}
In PHP, it would be terribly inefficient. You would have to loop through each row and check that its name was trout. However, is there any reason you can't do
SELECT * FROM `animals` WHERE `type` = 'fish' AND `name` = 'trout'
in SQL? It would be much, much faster.
You can also do something like
select morestuff from (select stuff from table where a = b ) where c = d;
Use the AND keyword?
"SELECT * FROM animals WHERE type = 'fish' and name='trout'"
Also, you can use LINQ for php http://phplinq.codeplex.com/
Related
Hi there i am working on PHP code that is selecting columns from two tables.
Here is my code:
$result2 = mysql_query("SELECT *
FROM `videos`, `m_subedvids`
WHERE `videos.approved`='yes' AND
`videos.user_id`='$subedFOR'
ORDER BY `videos.indexer`
DESC LIMIT $newVID");
while($row2 = mysql_fetch_array($result2))
{
$indexer = addslashes($row2['videos.indexer']);
$title_seo = addslashes($row2['videos.title_seo']);
$video_id = addslashes($row2['videos.video_id']);
$title = addslashes($row2['videos.title']);
$number_of_views = addslashes($row2['videos.number_of_views']);
$video_length = addslashes($row2['videos.video_length']);
}
When i try to print $indexer with echo $indexer; it's not giving me any results.
Where is my mistake in this code?
It seems to me like the key 'indexer' isn't in your results. It's hard to tell, since you haven't listed a definition for your table and you're using SELECT * so we can't see the names.
It makes the program easier to read later, if instead of SELECT *..., you use SELECT col1, col2, .... Yes, SELECT * will save you some typing right now, but you'll lose that time later when you or anyone else who works on your code has to check the table definition every time they work with that line of code.
So, try changing your query to explicitly select the columns you use. If it's an invalid column you'll get an error right away rather than this silent failure you're getting now, and you'll thank yourself later as well.
So long as videos.indexer is a unique field name among all tables used in the query you can change
$indexer = addslashes($row2['videos.indexer']);
to
$indexer = addslashes($row2['indexer']);
You don't need to (or can not) use the table name when referring to the result.
I have just started to convert to mysqli due to the added security benefits. The main reason for converting to mysqli was the mysqli_multi_query function though. I had several long, complicated query's with a lot of JOINS in and when I found out about this function I thought I could make it simpler by breaking everything down into separate queries.
However, I have been unable to get the query to work as I want it to and the PHP manual isn't helping me.
Here's what I have so far;
$qry = "SELECT T.T_ID, T.name, T.pic, T.timestamp AS T_ts,
(SELECT COUNT(*) FROM track_plays WHERE T_ID = T.T_ID) AS plays,
(SELECT COUNT(*) FROM track_downloads WHERE T.T_ID = T_ID) AS downloads
FROM tracks T WHERE ID = '$ID';
";
$qry .= "SELECT S_ID, status, timestamp AS S_ts FROM status WHERE ID = '$ID';";
$qry .= "SELECT G_ID, gig_name, date_time, lineup, price, ticket, venue, G_pic, timestamp AS G_ts FROM gigs WHERE ID = '$ID'";
// Execute multi query
if (mysqli_multi_query($con,$qry)){
do {
// Store first result set
if ($result=mysqli_store_result($con)){
while ($row=mysqli_fetch_array($result)){
print_r($row);
}
}
}
while (mysqli_next_result($con));
}
This works fine and the array is printed as expected. However, i want to set a lot of variables for use later on. I won't list all of the variables but I have a few like this;
$S_ID = htmlspecialchars($row['S_ID']);
$T_ID = htmlspecialchars($row['T_ID']);
$G_ID = htmlspecialchars($row['G_ID']);
The variables are retrieved but due to the loop nature of the function PHP errors are given as well saying the $S_ID or $G_ID are undefined. $T_ID does not get an undefined error as it is the first query as is not looped over.
If you need any more information or I have not explained well enough just ask!
A while back ago i have had the same issues, and also for the same reason i have migrated from mysql to mysqli.
Sadly, it wasnt the best sollution for many cases, as i have realized on the way.
While implementing stuff with mysqli and multi query i still have had some issues that i had with mysql.
The solution i recommend, is to use views on your complicated querys.
it makes your coding and querys far less complicated.
I know it is not the answer you have been looking for, but give it a thought.
So far, every time I use a mysqli_multi_query, my do-while condition is:
while(mysqli_more_results($connection) && mysqli_next_result($connection));
You may like to replace your while statement and see if that helps.
If not, are you differentiating between each subsequent query when you are assigning these $S_ID, $G_ID variables? Are you inadvertently overwriting a variable with an empty $row[] value?
I also didn't see mysqli_free_result($result) in your code.
I'll even offer some error checking as a garnish.
preg_match_all("/(?:SELECT\s(.*?),\s.*?(?:;|$))/",$qry,$first_columnname);
if (mysqli_multi_query($con,$qry)){
do {
if ($result=mysqli_store_result($con)){
$query_identifier=array_shift($first_columnname[1]);
while ($row=mysqli_fetch_array($result)){
if($query_identifier)=="T.T_ID"){
//do something...
}elseif($query_identifier)=="S_ID"){
//do something...
}elseif($query_identifier)=="G_ID"){
//do something...
}
}
mysqli_free_result($result);
}
}
while(mysqli_more_results($con) && mysqli_next_result($con));
}
if($error_mess=mysqli_error($con)){echo "Error = $error_mess";}
Let me know if any of these small changes do the trick.
This might be a simple question, but I can't find a definitive answer I can understand. I use PHP loops alot, I'm fairly new to PHP so they are usually simple like so:
<?php
$result = mssql_query("SELECT Price FROM Window_Extras WHERE ExtraID = '4' ");
while ($row = mssql_fetch_array($result)) {
?>
<a title="<?php echo $row['Colour']; ?>"></a>
<?php }?>
Is a really simple example, that doesn't make much sense, but I hope it shows how I use them. The question I wanted to ask was if $row and $result have to be named that for it to work, could they for example be named $priceresult and $pricerow?
This is because sometimes I would like to use multiple queries for a single loop, for example:
<?php
$result = mssql_query("SELECT Price FROM Extras WHERE ExtraID = '4' ");
$colourresult = mssql_query("SELECT ColourID FROM Colours WHERE Type = '8' ");
while ($row = mssql_fetch_array($result, $colourresult)) {
?>
This however didn't work, when I tried to echo out:
<?php echo $row['ColourID']; ?>
Can anyone tell me how I should be approaching this, and if I am at all on the correct track. Sorry if I havn't explained it very well.
To answer your first question:
Yes, you can use any variable name you like for the result and row variables. PHP doesn't care what you call them, and in fact it's perfectly possible to have several of them in use at any given time, in which case they obviously need to have different names.
You then followed up that question by asking why the following code doesn't work:
$result = mssql_query("SELECT Price FROM Extras WHERE ExtraID = '4' ");
$colourresult = mssql_query("SELECT ColourID FROM Colours WHERE Type = '8' ");
while ($row = mssql_fetch_array($result, $colourresult)) {
....
}
The reason for this is that the _fetch_array() function can only work with one set of results at a time. You would need to fetch a separate row array for each of them.
It's not clear what you're trying to do with these two queries, and why you would want to put them into the same loop together in the way you've shown.
I'm going to assume that the two queries are linked in some way that makes it logical for you to use them together like this? Perhaps the Extra item you're loading has a known Colour; ie you know that the Extra item numbered 4 is coloured with the Colour numbered 8?
Typically a program wouldn't be written with this knowledge; it would be part of the data. So in the Extras table, you would have a ColourID field, which would contain the value 8. The program would load the Extras record, see that the ColourID was set, and then load the matching Colours record according to what it saw.
Thus, your code could look something like this:
$result = mssql_query("SELECT Price FROM Extras WHERE ExtraID = '4' ");
while ($row = mssql_fetch_array($result)) {
$colourresult = mssql_query("SELECT ColourID FROM Colours WHERE Type = '".$row['colourID']."' ");
while ($row2 = mssql_fetch_array($result)) {
....
}
}
Inside the inner while loop, you could then access fields from either query, using $row or $row2 respectively (again, you can name these as you see fit).
However, that's not the end of the story, because SQL actually has the ability to merge these two queries into one without needing all that PHP code, using a thing call a SQL JOIN.
Now we can write a more complex query, but go back to having simpler PHP code:
$result = mssql_query("SELECT Extras.Price, Colours.ColourName FROM Extras WHERE ExtraID = '4' INNER JOIN Colours ON Colours.ColourID = Extras.ColourID");
while ($row = mssql_fetch_array($result)) {
....
}
If you're a beginner in PHP and SQL, these concepts are all probably new to you, so I advise trying them out, experimenting with them, and most importantly, reading a few (good quality) tutorials about them before proceeding much further.
Hope that helps. :)
(PS: as I said above, make sure you're reading good tutorials; beware of bad PHP examples and teaching sites -- there's a lot of them out there, teaching poor code and obsolete techniques; make sure you're reading something worthwhile. A good place to start might be http://phpmaster.com/)
This is because mssql_fetch_array can only take one result set. So removing $result and leaving $colourresult should work for you.
See: http://php.net/manual/en/function.mssql-fetch-array.php
Your variables ($...) can be called whatever you want, it's generally better to name them in a way that you can understand, hence most of the examples in the PHP Manual contain variables like $row, $result, $query, etc.
In terms of your database query, you can only pass one query to the mssql_query method. If you have data from different tables that you need to display, you should try and join the tables if possible using SQL rather than looping through multiple result sets.
I'm writing a filter/sorting feature for an application right now that will have text fields above each column. As the user types in each field, requests will be sent to the back-end for sorting. Since there are going to be around 6 text fields, I was wondering if there's a better way to sort instead of using if statements to check for each variable, and writing specific queries if say all fields were entered, just one, or just two fields, etc.
Seems like there would be a lot of if statements. Is there a more intuitive way of accomplishing this?
Thanks!
Any initial data manipulation, such as sorting, is usually done by the database engine.
Put an ORDER BY clause in there, unless you have a specific reason the sorting needs done in the application itself.
Edit: You now say that you want to filter the data instead. I would still do this at the database level. There is no sense in sending a huge dataset to PHP, just for PHP to have to wade through it and filter out data there. In most cases, doing this within MySQL will be far more efficient than what you can build in PHP.
Since there are going to be around 6 text fields, I was wondering if there's a better way to sort instead of using if statements to check for each variable
Definitely NO.
First, nothing wrong in using several if's in order.
Trust me - I myself being a huge fan of reducing repetitions of code, but consider these manually written blocks being the best solution.
Next, although there can be a way to wrap these condition ns some loop, most of time different conditions require different treatment.
however, in your next statements you are wrong:
and writing specific queries
you need only one query
Seems like there would be a lot of if statements.
why? no more than number of fields you have.
here goes a complete example of custom search query building code:
$w = array();
$where = '';
if (!empty($_GET['rooms'])) $w[]="rooms='".mesc($_GET['rooms'])."'";
if (!empty($_GET['space'])) $w[]="space='".mesc($_GET['space'])."'";
if (!empty($_GET['max_price'])) $w[]="price < '".mesc($_GET['max_price'])."'";
if (count($w)) $where="WHERE ".implode(' AND ',$w);
$query="select * from table $where";
the only fields filled by the user going to the query.
the ordering is going to be pretty the same way.
mesc is an abbreviation for the mysql_real_escape_string or any other applicable database-specific string escaping function
select * from Users
order by Creadted desc, Name asc, LastName desc, Status asc
And your records will be sorted by order from query.
First by Created desc, then by Name asc and so on.
But from your question I can see that you are searching for filtering results.
So to filter by multiple fileds just append your where, or if you are using any ORM you can do it through object methods.
But if its simple you can do it this way
$query = "";
foreach($_POST['grid_fields'] as $key => $value)
{
if(strlen($query) > 0)
$query .= ' and '
$query .= sprintf(" %s LIKE '%s' ", mysql_real_escape_string($key), '%' .mysql_real_escape_string($value) .'%');
}
if(strlen($query) > 0)
$original_query .= ' where ' . $query;
this could help you to achieve your result.
No. You cannot avoid the testing operations when sorting the set, as you have to compare the elements in the set in same way. The vehicle for this is an if statement.
Could you take a look at this?
WHERE (ifnull(#filter1, 1) = 1 or columnFilter1 = #filter1)
and (ifnull(#filter2, 1) = 1 or columnFilter2 = #filter2)
and (ifnull(#filter3, 1) = 1 or columnFilter3 = #filter3)
and (ifnull(#filter4, 1) = 1 or columnFilter4 = #filter4)
and (ifnull(#filter5, 1) = 1 or columnFilter5 = #filter5)
and (ifnull(#filter6, 1) = 1 or columnFilter6 = #filter6)
Please let me know if I'm misunderstanding your question.. It's not like an IF statement batch, and is pretty lengthy, but what do you think?
I need to grab data from two tables, but I know theres a better, more tidier way to do this. Is it some kind of JOIN i need?
I'll show you my code and you'll see what I mean:
if ($rs[firearm] != "") {
$sql_result2 = mysql_query("SELECT * FROM db_firearms WHERE name='$rs[firearm]'", $db);
$rs2 = mysql_fetch_array($sql_result2);
$sql_result3 = mysql_query("SELECT * FROM items_firearms WHERE player='$id'", $db);
$rs3 = mysql_fetch_array($sql_result3);
if ($rs3[$rs2[shortname]] < 1) {
mysql_query("UPDATE mobsters SET firearm = '' WHERE id ='$id'");
}
}
This question is clear, but your code example has alot of formatting issues and I cannot give you direct answer, based on your example code.
The reason, why your example is unclear, is because.. with what are you going to join the tables? From one table you are selecting by name='$rs[firearm]' and from another by player='$id'. You have to provide the hidden data, like $rs and also $id.
You should definitely read these about mysql join and mysql left join. But I will try to give you an example based on your code, with fixed syntax. (Keep in mind, that I'm no mysql join expert, I did not test this code and also I do not know the joining conditions.) And also, the system structure is unclear.
As I understood, this what your tables do, correct?
mobsters - Users table
items_firearms - Links from users table to items table
db_firearms - Items table
So basically, my example does this: It will have preloaded $rs value, from the users table. It will check, if there is a entry inside the links table and hook the result with them items table. However, if the links table or even the items table can return multiple entries, then this doesn't work and you need to loop your results in much more smarter way.
// I can only assume, that $id is the ID of the player
$id = 2;
// Since I dont know the $rs value, then Im going to make some up
$rs = array(
'id' => 33,
'firearm' => 'famas'
);
if ($rs['firearm']) {
$result = mysql_fetch_array(mysql_query("SELECT ifa.*, dbfa.* FROM `items_firearms` AS `ifa` LEFT JOIN `db_firearms` AS `dbfa` ON `ifa.shortname` = `dbfa.shortname` WHERE `ifa.player` = '$id'"));
if ($result['id']) {
mysql_query("UPDATE `mobsters` SET `firearm` = '' WHERE `id` = '$id'", $db);
}
}
It is pretty clear, that you are new to PHP and mysql.. So I think you should probably edit your question and talk about your higher goal. Briefly mention, what your application are you building..? What are you trying to do with the mysql queries..? Maybe provide the table structure of your mysql tables..? I'm sure, that you will get your questions votes back to normal and also we can help you much better.
NOTES
You have to quote these types of variables: $rs[firearm] -> $rs['firearm']
If you want to check if your $rs['firearm'] equals something, then there is a better way then $rs[firearm] != "". The most simple is if ($rs['firearm']) {echo 'foo';}, but will produce a notice message, when all errors reporting mode. You can use isset() and empty(), but keep in mind, that isset() checks whether the variable has been set.. Meaning, even if its false, then it has been set. empty() reacts to undefined and empty variable the same, without any messages.
Also, "" means NULL, so if you even need to use "", then use NULL instead...much neater way..
I strongly recommend to use mysql class. You can understand the basics behind that idea from this answer. This is gonna make things much more easier for you. Also, mysql class is a must-have when dealing with dynamic applications.
if ($rs3[$rs2[shortname]] < 1) { .. makes no sense.. Do you want to check if the value is empty? Then (simple): if (!$rs3[$rs2[shortname]]) { .. and a very strict standard: if (empty($rs3[$rs2[shortname]])) { ..
Also you have to quote your sql queries, see my examples above.
Is the last mysql query missing $db?