SQL UPDATE statement with LEFT JOIN, GROUP BY and HAVING? - sql

Question

I need to update some rows in a table. I've created a Select statement to make sure I've got the rows I wanted to select.
I want to update task_status_id in the table task, and I've tried in various ways but always end up with a syntax error and have honestly no idea how to do so even though I've tried to follow others examples by using INNER JOIN and putting the select statement in parenthesis. Any help would be appreciated.
UPDATE statement to merge with the SELECT statement.
UPDATE task
SET task_status_id = (SELECT task_status_id
FROM task_status
WHERE task_type_id = 1
AND name = 'Completed');
WHERE
SELECT
t.task_id
FROM task t
LEFT JOIN user u
ON t.user_id = u.user_id
LEFT JOIN contract co
ON u.user_id = co.user_id
LEFT JOIN task_status ts
ON t.task_status_id = ts.task_status_id
WHERE co.status = 'Closed' AND
t.task_type_id = 1 AND
t.task_status_id != (SELECT task_status_id
FROM task_status
WHERE task_type_id = 1
AND name = 'Completed')
GROUP BY t.task_id
HAVING count(t.contract_id) <= 2;

Answer 1

First of all, it doesn't make sense to use LEFT JOIN contract co and then filter results using co.status = 'Closed', because if you're going to filter by a column from a joined table then you should use INNER JOIN (unless you're comparing to null in the filter).
Secondly, syntax here is incorrect - you should use not in instead of !=
AND t.task_status_id != (SELECT task_status_id
FROM task_status
WHERE task_type_id = 1
AND name = 'Completed')
However, since you already joined the task_status table you can replace the above block of code with the following (assuming that task_status_id is a unique column):
AND ts.name != 'Completed'
Either way, you should post sample data and expected result.