Mysql using coalece within update statement

How would I use coalesce within an update statement. All example I have seen use select statement.

UPDATE d.n n JOIN d.o o ON n.ID = o.ID SET n.OC = o.OC
开发者_高级运维

need n.oc to Coalesce( n.oc,0) but Sql failed

CALL SQLExecute(CONCAT('UPDATE d.n  n JOIN data.o_ o ON n.id = o.id SET COALESCE(n.OC, null) = o.OC' ));  

Your query UPDATE d.n n JOIN data.o_ o ON n.id = o.id SET COALESCE(n.OC, null) = o.OC does not make sense. COALESCE(x,y) uses x if x is not null, otherwise it uses y.

So your query should be

UPDATE d.n  n JOIN data.o_ o ON n.id = o.id SET n.OC = o.OC //if null allowed

or this

UPDATE d.n  n JOIN data.o_ o ON n.id = o.id SET n.OC = COALESCE(o.OC,'somevalue') //if null not allowed

Oh, my. You CAN'T update function!

SET n.OC = COALESCE(o.OC, 0) 

at least