Check ALL empty comlumn in PHP & MySQL - php

Question

Ex : I have 1 table below
ID USER1 USER2 USER3
1 X X
2 X X
3 X X
4 X X
5 X X
How i can check ALL value USER2 comlumn is empty in PHP & MySQL? I code below but it's not working
$res = mysqli_query($conn, "SELECT USER2 FROM TABLE")
if(count($res)== "0") echo "OK";

Answer 1

select sum(user2 <> '') as count
from your_table

Answer 2

This would help,
$res = mysqli_query($conn, "SELECT COUNT(*) AS count FROM TABLE where USER2 IS NULL OR USER2=''");
if($res['count']==0)
{
echo "It is Empty";
}
else
{
echo $res['count']." rows have User2 empty";
}
count(*) returns the no of rows coming as the output of the query, which will be in integer form. $res == "0" means that you are comparing with a string "0", not an integer.

Answer 3

$res = mysqli_query($conn, "SELECT * FROM TABLE where USER2=''")
$n_rows_void_user2 = mysql_num_rows($res);
if($n_rows_void_user2) echo "OK";
else
echo "There are $n_rows_void_user2";

Answer 4

First of all you have to write the correct query:
"SELECT * FROM mytable WHERE --user2 condition--"
Where user2 condition may be different depend on your data:
WHERE ISNULL(user2) OR user2=''
It depends on your data.
Then to execute this query in php:
$res = mysqli_query($conn, $query);
$n_rows = mysql_num_rows($res);
if ($n_rows > 0) {
// echo your rows here
}
Also you should connect to database before, i hope you did that.

Answer 5

you can do something like this:
$res = mysqli_query($conn, "SELECT * FROM TABLE where USER2 IS NULL OR USER2 = ''");
$num = $res->num_rows;
if($num != 0){
echo "number of empty row for USER2".$num;
}else{
echo "on empty column for USER2";
}

Answer 6

An extension to the answer by #juergen :
select sum(user2 IS NOT NULL OR some_col <> '') as count
from your_tabl;