Accessing only part of a Database value

[MortimerJazz]

Hi there,

I'm currently writing a form where a user will input the first three characters of a postcode.

In my database I have registered users full postcodes, but when I run my query I only want to match the from the form to the first three letters of the database value.

I'm currently using the following query:
[code]$sql_postcode_check = mysql_query("SELECT username, postcode
  FROM users
  WHERE left(cast(postcode as string), 3) = '$postcode'");[/code]

But I'm getting an error message saying that the supplied argument is not a valid MySQL result resource.

Can anyone tell me what I'm doing wrong?

Thanks

[paul2463]

add an or die at the end of the query and find out why the result resource is not there

[code]
$sql_postcode_check = mysql_query("SELECT username, postcode FROM users WHERE left(cast(postcode as string), 3) = '$postcode'") or die ('Error in Query ' . mysql_error())
[/code] ;

[MortimerJazz]

Thanks Paul.

I'm getting the following error message:

[quote]right syntax to use near 'string), 3) = 'SL9'' at line 3[/quote]

SL9 is what I typed into the form field.

[paul2463]

it seems it does not like your WHERE statement - try this one then, its worth a go(tested the substring() function on PHPMyAdmin and it works on another table I have with postcodes in it
[code]
$sql_postcode_check = mysql_query("SELECT username, postcode FROM users WHERE SUBSTRING(postcode,1,3) = '$postcode'") or die ('Error in Query ' . mysql_error())
[/code]