check a value in DB?

[craigh]

what would be the smartest/most efficient way to check to see if a value exists in a table?

example:

I have $value = "R"

I have a table called letters that contains several rows:

ID | letter

1 | M
2 | L
3 | S
4 | R

how can I check to see if $value exists in 'letters' most efficiently? I don't care where it appears, just that it exists.

[andreash]

$value = "R";

$foo = mysql_query("Select * form TABLENAME where letter='$value'");
$num = mysql_num_rows($foo);

if $num equals 0 (zero), R does not exist in the table.

[craigh]

Thanks - that works very well.