you're using left outer join to locate rows in A for which there is
missing a row in B. the more idiomatic SQL for this is:
UPDATE a SET a.y=1 WHERE NOT EXISTS (SELECT * FROM b WHERE a.x = b.x)
works on any DB and performs better too.
On 11/05/2016 09:38 PM, T Johnson wrote:
How do I do an update join using SQLAlchemy core? In MySQL, it'd be something
like this:
update a left outer join b
on a.x = b.x
set a.y = 1
where b.x is null
In other words, I want to modify a but only for the rows that do not exist in b
according to my join criterion. The naive attempt that calls update() on the
join object fails since Join objects don't have an update attribute. As a
workaround, I'm using text().
A similar question on stackoverflow used an innerjoin and so it could be
rewritten without needing an explicit join:
http://stackoverflow.com/q/28274133/1843746
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