Simple MySQL if query syntax

Question

edit: my table schema below is poorly normalized as suggested and I have revamped it.

schema

wait, why is there varieble after select? what is the column you are trying to get? Do you have special column for every user? — Milan Halada
– Milan Halada, Commented Mar 28, 2012 at 13:01
It tells me that "It's NULL!". I tried to echo back ($result) but it gives me nothing at all? — Kel196
– Kel196, Commented Mar 28, 2012 at 13:04
I am using PHP to write these SQL statements. The variables are values extracted from an android form and that side works, as do the variables. My SQL, though, isn't very good and I think that is where the error is coming from. — Kel196
– Kel196, Commented Mar 28, 2012 at 13:06
can you please add your table structure, i believe problem is wrong query — Milan Halada
– Milan Halada, Commented Mar 28, 2012 at 13:08

Milan Halada · Accepted Answer · 2012-03-28 13:26:25Z

2

Try to use mysql_num_rows() in your condition

if (mysql_num_rows($result) == 0) {
    echo (" It's NULL!");
    // if null, run a query!
} else {
echo (" It's not null...");
// if not null, echo back meessage saying not null.
}

EDIT: nevermind

EDIT2: Gosh, I see it now, try

$row = mysql_fetch_assoc($result);

if ($row[$userid] == NULL) {
    echo (" It's NULL!");
    // if null, run a query!
} else {
echo (" It's not null...");
// if not null, echo back meessage saying not null.
}

edited Mar 28, 2012 at 13:26

answered Mar 28, 2012 at 12:59

Milan Halada

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4 Comments

Kel196 Over a year ago

weirdly, i've made each individual user have individual columns so that i can store their question responses in each one. Check this image of my table to see if you get what I mean... s21.photobucket.com/albums/b259/acidburn942/…

user1269636 Over a year ago

Your last example will probably work, but this is a really bad idea to store users in columns. OP: You might want to reconsider your data schema because this is badly normalized and not scalable at all.

Milan Halada Over a year ago

I know, just trying to solve the current problem, not even pointing out possible sql injection vulnerability. Redesigning that db would be best solution

Kel196 Over a year ago

Pierre-OlivierBourgeois and Uriel_SVK thank you very much for both your input. Uriel's solution does now solve the problem but I am always learning! I will look more into my database structure and try to make it better. Thank you for the tips Pierre!

user1269636 · Accepted Answer · 2012-03-28 13:02:07Z

1

Try using mysql_num_rows() for checking how many rows are returned,

if (mysql_num_rows($result) == 0)
{
    echo (" It's NULL!");
    // if null, run a query!
}
else
{
    echo (" It's not null...");
    // if not null, echo back meessage saying not null.
}

Also, what column are you trying to select ?

answered Mar 28, 2012 at 13:02

user1269636

4 Comments

Kel196 Over a year ago

here is my table structure: s21.photobucket.com/albums/b259/acidburn942/… the column i am trying to select is userid, to check if it is null according to a certain question id....

user1269636 Over a year ago

You used a column per user ? This is poorly normalized. Take a look at this: asciiflow.com/#5355087028660164263/2004018477

user1269636 Over a year ago

And then, you could do a SELECT COUNT(1) from userAnswers WHERE id = $qid AND userid = $userid which will return you the number of rows for this specific condition.

Kel196 Over a year ago

Thank you very much, this is my first attempt at a questions/answer database. I will look more into my database structure and try to improve it! :)

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