Complex update query - mysql

Question

Table 1
|id|name|address|car_id |
|1 |Alex|US |NULL |
|2 |Jaso|Canada |1 |
Table 2
|car_id|color|
|1 |red |
|2 |blue |
I am trying to update Alex's car_id with the car_id of the blue car in the second table. Is it possible to do it in one query?
I tried writing the query below, but couldn't make it work. Any ideas?
UPDATE table1
SET table1.car_id = table2.car_id
FROM table1
JOIN table2
ON table2.color = "blue"
WHERE table1.name = "Alex"
Desired result:
|id|name|address|car_id |
|1 |Alex|US |2 |
|2 |Jaso|Canada |1 |

Answer 1

I suspect it does not work in one query. [Edit: Wrong, see other answer]
You have 2 different requirements for 2 different tables which do not have a common column.
You need to find the blue car_id independently from Alexes row as they are not linked in any way by now.
I would do it as follows:
UPDATE
table1
SET
table.car_id = (
SELECT
car_id
FROM
table2
WHERE
color LIKE 'blue'
)
WHERE
name LIKE 'Alex'

Answer 2

update firstTable join secondTable on secondTable.color = 'blue' set firstTable.car_id = secondTable.car_id where firstTable.car_id is null;

Answer 3

I have a solution for a similar problem with more people and more cars.
Maybe it helps DBfiddle example
The base datatabke are as follows
CREATE TABLE Table1
(`id` int, `name` varchar(4), `address` varchar(7), `car_id` varchar(4))
;
INSERT INTO Table1
(`id`, `name`, `address`, `car_id`)
VALUES
(1, 'Alex', 'US', NULL),
(2, 'Jaso', 'Canad a', '1'),
(3, 'Paso', 'Canad a', NULL),
(4, 'Paso', 'danad a', NULL)
;
CREATE TABLE Table2
(`car_id` int, `color` varchar(7))
;
INSERT INTO Table2
(`car_id`, `color`)
VALUES
(1, 'red'),
(2, 'blue'),
(3, 'green') ,
(4, 'purple')
;
The sql statement for mysql till 5.7
Update Table1 t1a inner Join
(Select tab1.id, tab2.car_id From
( Select
`id`,
#curRank := #curRank + 1 AS rank
FROM Table1, (SELECT #curRank := 0) r
WHERE car_id IS NULL ) tab1
inner join
( Select
car_id,
#curRank2 := #curRank2 + 1 AS rank
From Table2 , (SELECT #curRank2 := 0) r Where car_id NOT IN
(
Select Car_id From
(Select GROUP_CONCAT(t1.car_id) car_id FROM Table1 as t1) t1e
WHERE car_id IS NOT NULL GROUP BY car_id
)
) tab2
ON tab1.rank = tab2.rank) t2a
on t1a.id = t2a.id
SET t1a.car_id = t2a.car_ID
;
The Problem that we face here is that we need actually the car_ids from table taht are already taken. And then select only rest of the car_id, that are not selected yet.
After that we have to make the statement so that ver person gets one color ann that every colour is selected only once. that takes a little code because we have no relationship betwenn tabel1 car_ids thta are NULL and table2.
So result is
id name address car_id
1 Alex US 2
2 Jaso Canad a 1
3 Paso Canad a 3
4 Paso danad a 4
With mysql 8 you use window function instead of the vehicle rank.