Viewed   120 times

I work with xampp. I performed MySQL connection:

$connection = mysql_connect($host , $user , $passw);
mysql_select_db($db, $connection);

I received output with echo command (by check the boolean returned values) that connection is established and the database $db is found.

But the simplest query like:

$query = mysql_query("SELECT * FROM 'users'");

returns false. How can I debug why?Thanks.



An obligatory update: as mysql ext is no more, here are answers for two remaining MySQL APIs which I written on my site based on the experience from answering 1000s questions on :

  • How to report errors in mysqli
  • How to connect to MySQL using PDO (with the aim of the proper error reporting).

In short, for mysqi the following line have to be added before mysqli_connect() call:


while for PDO the proper error mode have to be set, for example


As of the old mysql ext,

To get an error from mysql_query() you have to use mysql_error() function.
So always run all your queries this way, at least until you develop a more advanced query handler:

$query = "SELECT * FROM 'users'";
$result = mysql_query($query) or trigger_error(mysql_error()." ".$query);

the problem with your current query is 'users' part. Single quotes have to be used to delimit strings while for the identifiers you have to use backticks:

SELECT * FROM `users`

In order to see these errors during development, add these lines at the top of your code to be sure you can see every error occurred


on the production server, however, the value on the first line should be changed from 1 to 0

Sunday, August 21, 2022

I would say just build it yourself. You can set it up like this:

$query = "INSERT INTO x (a,b,c) VALUES ";
foreach ($arr as $item) {
  $query .= "('".$item[0]."','".$item[1]."','".$item[2]."'),";
$query = rtrim($query,",");//remove the extra comma
//execute query

Don't forget to escape quotes if it's necessary.

Also, be careful that there's not too much data being sent at once. You may have to execute it in chunks instead of all at once.

Saturday, November 5, 2022

The function you're looking for is find_in_set:

 select * from ... where find_in_set($word, pets)

for multi-word queries you'll need to test each word and AND (or OR) the tests:

  where find_in_set($word1, pets) AND find_in_set($word2, pets) etc 
Wednesday, August 17, 2022

Perhaps you could create an indexing table which provides a sequential key relating to the key in your target table. Then you can join this indexing table to your target table and use a where clause to more efficiently get the rows you want.

#create table to store sequences
   seq_no int not null auto_increment,
   id int not null,
   primary key(seq_no),

#create the sequence
INSERT INTO seq (id) SELECT id FROM mytable ORDER BY id;

#now get 1000 rows from offset 1000000
SELECT mytable.* 
FROM mytable 
WHERE seq.seq_no BETWEEN 1000000 AND 1000999;
Thursday, October 6, 2022
mysql>show processlist;

mysql> kill "number from first col";
Thursday, December 22, 2022
Only authorized users can answer the search term. Please sign in first, or register a free account.
Not the answer you're looking for? Browse other questions tagged :