WHERE clause in INSERT statement using mysql/php [closed] - php

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After searching on Google, i came to know that,
I can not use a WHERE clause in my INSERT query..
But i want to insert a value on column "Book_4" where "Student_ID = 1"
How can i do that ??
Is there any alternate to do that ?
Will be Thankful to You !
$Query = "INSERT INTO issued_books (Book_4) VALUES ('$IssuedBookNumber')" ;
EDITED:
More Details
Using insert query, when i insert a value in column "Student_ID" in my table. All columns in the row of Student_ID (except Student_ID) shows 0 in my DB.
I dun know what this 0 means according to DB.
It might be Null or numeric 0.
If it is a numeric 0, then it should be updated using the UPDATE statement.
But whenever i'm trying to update it, it never updates using UPDATE statement. That's why i'm asking !
P.S: All columns have Datatype INT.
Hope you understand what i want to say :)
Here is the complete code.
Suppose: Student_ID is already created having the value 2.
IssuedBookNumber = 51
Using the above values:
Result = A new row is created having all columns 0 except the column "IssuedBookNumber" that is having value = 51.
While i want, the result should be:
On row Student_ID = 2, Book_4 should be 51.
The point is, When i inserted a value on Student_ID, all other columns becomes 0 on the same row. But when any of the column on the same row having any number except the 0 (that was automatically came on all columns when i inserted a value in Student_ID). Update Query will work.. !
$IssuedBookNumber = $_POST['IssuedBookNumber'];
$Student_ID = $_POST['StudentId'];
$FetchingQuery = "SELECT * FROM issued_books WHERE Student_ID='" . $Student_ID . "'";
$RunFetchingQuery = mysql_query($FetchingQuery);
while ( $row = mysql_fetch_array( $RunFetchingQuery ) ) {
$Book_1 = $row[ 'Book_1' ];
$Book_2 = $row[ 'Book_2' ];
$Book_3 = $row[ 'Book_3' ];
$Book_4 = $row[ 'Book_4' ];
$Book_5 = $row[ 'Book_5' ];
}
if(!empty($Book_4))
{
$Update = "UPDATE issued_books SET Book_4='$IssuedBookNumber' WHERE Student_ID= '$Student_ID'";
mysql_query ($Update);
}
else
{
$AddQuery = "INSERT INTO issued_books (Book_4) VALUES ('$IssuedBookNumber')";
mysql_query ($AddQuery);
}

Answer 1

That not an INSERT. That's an UPDATE. INSERT statements insert a new row. UPDATE statements update an existing row.
UPDATE issued_books
SET Book_4 = '$IssuedBookNumber'
WHERE Student_ID = '$Student_ID'
(I'm assuming you've properly escaped $IssuedBookNumber and $Student_ID)

Answer 2

If you can add a unique index on the 2 columns combined (book_4, student_id)
This would be a good query andshould replace most of your code above
INSERT INTO issued_books (book_4, student_id) VALUES('$IssuedBookNumber','$Student_ID')
ON DUPLICATE KEY UPDATE
SET Book_4 = '$IssuedBookNumber';
Note: you while loop above is not needed since $Book_4 will always return the value of the last row.
your code will then look like this :)
$IssuedBookNumber = $_POST['IssuedBookNumber'];
$Student_ID = $_POST['StudentId'];
$Update = "UPDATE issued_books SET Book_4='$IssuedBookNumber' WHERE Student_ID= '$Student_ID'";
mysql_query ($Update);
Things you should consider,
Switch to using PDO or mysqli
Escape your variables are your code is vulnerable to a SQL injection. Perhaps after you switch to PDO or mysqli you can use prepare statement.

Answer 3

Why not something like this:
$Query = "INSERT INTO issued_books (Book_4, Student_ID)
VALUES ('$IssuedBookNumber', '$Student_ID')"

Answer 4

Use update statement.
update issued_books set Book_4 = $IssuedBookNumber
where Student_ID = '$Student_ID'