SQL update multiple rows with different values, without specifying unique key - php

Question

I need help building a SQL query which searches for an user_id (let's say user_id = 5), but this user_id has multiple row entries, but I need to update each row differently though.
I have an array with data which I want to assign to that user_id. Here is a table example:
id user_id amount txn_id
1 5 10 foo_unique
2 5 5 bar_unique
3 7 15 xyz_unique
4 5 10 123_unique
My array would look something like this:
Array (
[0] => 14
[1] => 6
[2] => 9
)
As you see I have three array values and three rows for user_id 5, now I want to add each value of that array, to the corresponding user_id (5). Note that I have an UNIQUE column named txn_id
After updating the table, it would look like this:
id user_id amount txn_id
1 5 14 foo_unique
2 5 5 bar_unique
3 7 6 xyz_unique
4 5 9 123_unique
Any ideas how I could achieve this?
Thanks.
P.S: I cannot use SQL CASE on this issue.

Answer 1

If you want to update one row with a value, you have to be able to have a unique condition for that row.
Without adding some extra field, or condition to uniquely identify a row, you are out of luck.

Answer 2

You can use the following query:
UPDATE MyTable
SET
amount =
CASE id
WHEN 1 THEN 14
WHEN 2 THEN 6
WHEN 3 THEN 9
ELSE amount -- just in case user_id 5 has records not covered above.
END
WHERE
user_id = 5

Answer 3

The problem is, there is nothing on your array that says which array entry belongs to which database row. If you want to rely just on the orders (of the array indices, and the database ids,), you have to SELECT all rows for the user first, then loop and update a row at a time. Something like this on PHP (and PDO):
$values = array(14, 6, 9);
$dbh = new PDO('mysql:host=localhost;dbname=yourdbname', 'username', 'password');
$selectQuery = 'SELECT id FROM yourtable WHERE user_id = 5 ORDER BY id';
foreach($dbh->query($selectQuery) as $row) {
$id = $row['id'];
$sth = $dbh->prepare("UPDATE yourtable SET amount = :val WHERE id = :id");
$sth->execute(array(
'val' => array_unshift($values),
'id' => $id
));
}
(Code above assumes the number of values on your arrays matches the number of database rows for user_id = 5).

Answer 4

Looking at the problem you only need to have SQL statements.
First is to create two tables:
CREATE TABLE users
user_id int(11) PRIMARY KEY NOT NULL,
username varchar(25),
) Engine = InnoDB;
CREATE table userbalances (
balance_id int(11) PRIMARY KEY NOT NULL,
user_id int(11),
amount decimal(10,2),
CONSTRAINT userid_fk FOREIGN KEY userid_fk(user_id) REFERENCES users(userid)
) Engine = InnoDB;
Then, after you have INSERT(ed) all of the users and userbalances inside the table, all you need to do is create an UPDATE statement to update the amount:
UPDATE userbalances SET amount=? WHERE user_id=? AND balanceid=?
The update should be in a loop. And you should use mysql_query() function to update it with the assigned arrays that you have.
Note:
Both userid and balanceid should be in the WHERE clause of your UPDATE statement because you have multiple transactions inside the userbalances table. Otherwise, it's going to change all of the balances of all the transactions of that user.
Problem update:
If you don't use any SQL Cases on this problem, then your problem is just PHP. You need to find out what is the function for UPDATE(ing) - to update the amounts. As long as your tables are all prepopulated. There might be a function on the program you use to update it.