Could I do this in a select statement where a WHERE condition has an OR
SELECT * from Table WHERE something = ? OR ?
You can if you follow the correct syntax. (Think of it like youāre writing any other languageā¦)
SELECT * from Table WHERE column_name1 = ? OR column_name1 =?
would that work?
Try it and see.
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This is my statement and in all cases it shows FALSEā¦even if trueā¦so there is something wrong with my condition
$sql = "SELECT * FROM student_progress WHERE student_id = ? AND level = ? OR level = ?";
Well, now youāre being ambiguous.
A And B Or C.
AB
AC
C
Which of these values would you expect this query to return? Why can I say that the correct answer is āI dont knowā?
(A) and (B or C)
But I could say that āA and B or Cā means (A and B) or C.
You notice how to convey what you mean to me, you have to put parenthesis? Thatās a hint. The database engine needs you to put the parenthesis too.
Yes I understand I need to group then. This is what I tried. I still get no-records each time
$level1 = 1;
$level2 = 2;
$sql = "SELECT * FROM student_progress WHERE (student_id = ?) AND (level = ? OR level = ?)";
$stmt = $conn->prepare($sql);
$stmt->execute([$sid,$level1,$level2]);
$result = $stmt->fetchAll(PDO::FETCH_ASSOC);
and what does $conn->errorInfo() tell you? (it returns an array)
print_r ($conn->errorInfo());
is that how I print the error?
Youād save yourself a lot of time not asking me if thats how you do X, and instead justā¦ run the code, and if what you get out the other end doesnt look like what you thought it should, then ask me what you did wrong 
I understand your frustration. I asked you AFTER I already ran the code LOL.
But I get no resultā¦it wont load the rest of my contentā¦just blank.
if youāve left that space in between the r and the (, then itās thrown a PHP error.
Yes there was indeed a space but that did not solve it. Here is how the code looks like so far.
$sql = "SELECT * FROM student_progress WHERE (student_id = ?) AND (level = ? OR level = ?)";
$stmt = $conn->prepare($sql);
$stmt->execute([$sid,$level1,$level2]);
print_r($conn->errorInfo());
(I see you typing there @Mittineague :P)
Right. Time to get superbasic then.
ini_set('display_errors', '1');
error_reporting(-1);
$sql = "SELECT * FROM student_progress WHERE (student_id = ?) AND (level = ? OR level = ?)";
$stmt = $conn->prepare($sql);
$stmt->execute([$sid,$level1,$level2]);
print_r($conn->errorInfo());
print_r($stmt->errorInfo());
die();
EDIT: That shoulda been a 1.
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AFAIK, MySQL has precedence rules
https://dev.mysql.com/doc/refman/8.0/en/operator-precedence.html
ā¦ The precedence of operators determines the order of evaluation of terms in an expression. To override this order and group terms explicitly, use parentheses. ā¦
i.e. AND will evaluate before OR
a AND b OR c evaluates as (a AND b) OR c
Personally, I resort to using parentheses to group not to override precedence but mainly because I donāt want to learn or look up precedence rules for the different use cases I work with. I find it a lot easier to use parentheses whether theyāre needed or not.
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Thank you for both your help! I changed the SELECT statement to this:
$sql = "SELECT * FROM student_progress WHERE (student_id = ?) AND ((level = ?) OR (level =
?))";
and it seems to work now
Yeah, pretty much the same thing - I canāt be bothered to remember precedence rules (And before Or in MySQL, but in PHP they have equal precedence so it becomes whatever occurs first in the statementā¦ etcā¦etcā¦)
Parenthesis just resolve all ambiguity
EDIT: Nope. Iām wrong, PHP has now separated and/or into separate precedence, but ā&&ā has precedence over ā||ā, but ā||ā has precedence over āandā. So. Yeah. Screw trying to remember it all
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You could replace repeated OR with IN
SELECT * FROM student_progress WHERE student_id = ? AND level IN (?,?)
FWIW
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