Is there a benefit or drawback to using the same variable to store the results of consequetive mysql queries, like this example?
$res = mysqli_query($conn, "UPDATE Research SET Progress=Progress+1 WHERE ID=1");
$res = mysqli_query($conn,"SELECT Progress FROM Research WHERE ID=1");
$res = mysqli_fetch_assoc($res);
I do it all the time. I copy and past those lines routinely. the only drawback is if you need an additional query while looping through the results of the first, in which case, things will get ugly. In those cases, you will need a unique name for the second query.
Related
Are these 2 equivalent, if not how can I make them. I'm using php/Mysql (I'll use mysqli later)
mysql_select_db("db_App", $link);
$result = mysql_query("SELECT * FROM AppOne");
OR
$result = mysql_query("SELECT * FROM db_App.AppOne"); // how can I get this to work like above?
You'll always have to select a database. From then on, specifying the database in the query is useless. It's better not to specify it there anyway, as that'd make you run into troubles if your database changes at some point.
if you skip the $link in mysql_select_db("db_App", $link);
they should do the same.
Im a php/mySQL newbie and am trying to get the hang of it. I have code to detect whether i get a username/password match, and now im trying to get the userid field so i can update the record. Heres what I have so far:
$sql = "SELECT username FROM users WHERE username='$username' AND password='$password'";
$result = $link->query($sql) or die(mysqli_error());
Using print_r($result) shows that there is an item, but im lost from here on out.
Try this.
$sql = "SELECT username FROM users WHERE username='$username' AND password='$password'";
$result = $link->query($sql) or die(mysqli_error());
while ($row = mysqli_fetch_array($result, MYSQLI_ASSOC)) {
$userID= $row['username'] ;
// If you need other field as userID just change the sql and the index of $row according to that.
}
EDIT
If you want to get only one row.
if($result->num_rows==1)
{
$row = $result->fetch_array(MYSQLI_ASSOC);
$userID = $row["username"];
}
Perhaps this will help. In any programming language, running an SQL query is going to consist of these steps:
Build the text of the SQL statement that you want to run.
(Optional) If your statement involves the use of parameters (or "placeholders"), prepare an array of the parameter-values that are to be substituted for each of them.
("Prepare" and...) "Run" the query, on some previously-opened "database connection." (In your example, "$link" must correspond to that connection.) This gives you a handle (you called it "$result") that corresponds to the zero-or-more rows that were returned by that query.
Now, use that handle to retrieve each of these rows, one at a time, until there are no more or until you're tired of doing it.
(Optional) Be neat and tidy and "close" the handle, thus indicating to the database system that it can discard all of the resources it was using to furnish those rows to you.
"Those, in simple terms, are the basic steps that every program in the known universe are going to go through," and if you now browse again through the PHP documentation, you'll see that there are functions that correspond to each of these steps. Browse through the chapters you've been reading and see if you can now match the up to the scenario I just described. HTH...
If I am doing a PHP MYSQL select of a table using the where clause that will return only 1 result, is there a simpler way to do this:
$result = mysql_query("select * FROM cart WHERE ID='".$cartID."'") or die(mysql_error());
$cartrec = mysql_fetch_array($result);
Is the $cartrec = mysql_fetch_array($result); needed or could I just do:
$cartrec = mysql_query("select * FROM cart WHERE ID='".$cartID."'") or die(mysql_error());
or is there a better syntax to use?
mysql_query gets a result set (actually, a resource that refers to a result set) based on your query. This is the set of records that match your query.
mysql_fetch_array gets the first record from a result set, and returns it as an array.
So, up until you've called mysql_fetch_array, you haven't gotten the data in a usable format.
Side note: Consider using PDO
The fetch array is required, the mysql_query gets a result set (ressource), then mysql_fetch_array get's the element in the result set.
As a side note, be careful of SQL injections: http://en.wikipedia.org/wiki/SQL_injection
EDIT: Might be a bit more advanced that what you need, but it might be worth while looking into PDO: http://php.net/manual/en/book.pdo.php
Is the $cartrec = mysql_fetch_array($result); needed
Yes, otherwise you get a resource pointer not an result set (array).
or is there a better syntax to use?
Yes, MySQLi
No, but its pretty common for people to write their own function for this use case. It's usually named something like fetch_one($sqlString) or fetch_first($sqlString)
You could use this, but if the database structure were to change, it would be problematic
$row = mysql_fetch_row($result);
echo $row[0]; //column 1
echo $row[1]; //column 2
You may want to look at this http://www.php.net/manual/en/function.mysql-fetch-row.php
Spent several hours searching for an answer without success. I've written a user-defined function in MySQL which is passed an identifier which it uses to retrieve various pieces of data, concatenate it into one string and return it. I want to call this function from my PHP page and output the result.
Unsuccessful attempts include:
1. $result = mysql_query("select functionName($id)");
2. $sql = "select functionName($id)";
$result = mysql_query($sql, $link);
3. functionName($id)
Any ideas?
1 and 2 are close, but $result is not going to contain the result of the function call. Rather, it is going to contain the result cookie from the query. You can use that cookie to get the actual data, with mysql_fetch_row(). The function call just returns a value for the select statement, just the same as "SELECT 42" or "SELECT a FROM MyTable". So to get the result you would use the same mechanism as with any other SQL query that returns results; that is, use the cookie and call mysql_fetch_row(). So your final code will look like this:
$result = mysql_query("select functionName($id)");
$row = mysql_fetch_row($result, $link);
$returnValue = $row[0];
Note that you don't want to be interpolating variables directly into an SQL string (that can be a vector for attacks). I assume, however, that this code is just for example purposes.
I had the same question and found this very useful write up from devx, particulary the part at the bottom about calling MySQL functions:
http://www.devx.com/webdev/Article/42887/0/page/2
With regards to mysqli, my code is now as follows:
$result = mysqli_query($sqlconnection,"SELECT functionName($id)");
$row = mysqli_fetch_row($result);
return $row[0];
works perfectly.
I am running this mysql query:
$result = mysql_query("SELECT * FROM userdetails WHERE userid= '$userid'");
$row = mysql_fetch_array($result);
The result is a row of 100 variables with different names such as $row['name'], and $row['email'], etc...
How can I convert all of these to just $name and $email, etc... in php?
It would save so much time to write this program....
Short anwser: extract
long anwser : don't. It may seem like a good anwser now but if you use it much it will become a problem keeping track of stuff.
http://au2.php.net/extract
You probably don't ultimately want to do that, but the extract() function does this.
http://us3.php.net/manual/en/function.extract.php