MySQL update multiple rows using arrays - mysql

Question

How can we update multiple rows at once in case of below stated data
studentId = [1,2,5,7,9]
marks = [25, 22, 27, 30, 24]
what will be the MySQL statement, if we want to update studentId 1 with 25 marks, studentId 2 with 22 marks, studentId5 with 27 marks and so on.
Please note: Have to update in 1 query only.
Thanks in advance :)

Answer 1

If you are using MySql 8.0+ you can create a CTE that returns the rows of the ids that you want to update and their marks and join it to the table:
WITH cte(studentId, marks) AS (VALUES
ROW(1, 25), ROW(2, 22), ROW(5, 27), ROW(7, 30), ROW(9, 24)
)
UPDATE tablename t
INNER JOIN cte c ON c.studentId = t.studentId
SET t.marks = c.marks
See the demo.
For previous versions, instead of the CTE you can join a query that uses UNION ALL:
UPDATE tablename t
INNER JOIN (
SELECT 1 studentId, 25 marks UNION ALL
SELECT 2, 22 UNION ALL
SELECT 5, 27 UNION ALL
SELECT 7, 30 UNION ALL
SELECT 9, 24
) c ON c.studentId = t.studentId
SET t.marks = c.marks
See the demo.

Answer 2

You could run one simple query five times, with different values:
UPDATE MyTable SET marks = ? WHERE studentId = ?
The idea is that you would write a loop in some application code, so you process the first element from each of your arrays. Then the second element of both arrays, and so on. For example in PHP:
$studentId = [1,2,5,7,9];
$marks = [25, 22, 27, 30, 24];
$stmt = $pdo->prepare("UPDATE MyTable SET marks = ? WHERE studentId = ?");
for ($i=0; $i<5; ++$i) {
$stmt->execute([$marks[$i], $studentId[$i]]);
}
From its earliest versions, SQL was always intended to be used in combination with an application language. Other languages have variables and loops and conditions and functions, which complement SQL. The easiest solution is to use these languages together.
If you really want to write a single UPDATE statement to update all five, it's possible, but it's really not as clear.
UPDATE MyTable
SET marks = CASE studentId
WHEN 1 THEN 25
WHEN 2 THEN 22
WHEN 5 THEN 27
WHEN 7 THEN 30
WHEN 9 THEN 24
END
WHERE studentId IN (1,2,5,7,9);
There are other clever ways of doing it in one statement, but all these solutions are hard to modify or maintain. They are needlessly complex.
I recommend doing it the simple way.