Warning</b>: Mysql_free_result (): supplied argument is not a valid MySQL result

What's wrong with that?

The connection has been shown to be successful, but the error is reported.

Connect to the database successfully!
Warning:  F:\environment\WAMP\wamp5\wamp\wamp\www\test\sql.php

Warning:  F:\environment\WAMP\wamp5\wamp\wamp\www\test\sql.php

Reply to discussion (solution)

$result = mysql_query ($sql);
Switch
$result = @mysql_query ($sql) or Die (Mysql_error ());

$result = mysql_query ($sql);
Switch
$result = @mysql_query ($sql) or Die (Mysql_error ());

The Web page shows the No database selected, this is not found this databases?
But I'm using the Navicat 8 for MySQL view tool.
I am here to create the database and resume the table. How should I query the tables in this database?

You only connected to the database system, but did not select the database to operate
mysql_select_db (' Library name ');
How else do you know that you are querying the user table in that library?

In addition, your mysql_close ($conn) is in the function, and the $conn is not passed to the function.
So there's going to be a 2nd mistake.

The moderator answers the perfect

$result = mysql_query ($sql);
Switch
$result = @mysql_query ($sql) or Die (Mysql_error ());

The Web page shows the No database selected, this is not found this databases?
But I'm using the Navicat 8 for MySQL view tool.
I am here to create the database and resume the table. How should I query the tables in this database?

You don't have mysql_select_db,mysql before mysql_query. You do not know which db you need to perform the query operation.

After creating the connection, add a sentence
@mysql_select_db (' Fill in database name ' here, $conn) or Die (Mysql_error ());

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