带有 CTE 的 BigQuery UPDATE 语句

Question

Looking for some help with BigQuery.

I can't seem to use CTEs in UPDATE statements, ie:

with ctename as
(select
    column1,
    column2,
    column3,
from blah)


update table2 
set table2.column2 = ctename.column2
from table2
inner join ctename
    on ctename.column1 = table2.column1

I can't find any reason as to why this shouldn't work in BigQuery. Any help/advice would be greatly appreciated.

Answer 1

I don't think BigQuery supports CTEs in updates. You can write this logic as:

update table2 
    set table2.column2 = (select blah.column2 from blah where blah.column1 = table2.column1)
    where exists (select blah.column2 from blah where blah.column1 = table2.column1);

Answer 2

Looks like below is equivalent of what you are trying to achieve, while technically preserving your cte's query (that obviously can be much much more complex than just select * from the blah)

update table2 
set column2 = ctename.column2
from (
  select column1, column2, column3
  from blah
) ctename 
where ctename.column1 = table2.column1    

Note: as it is implicitly comes from your question and from other answer(s) - it is expected that that there is 1:1 matches by column1 - otherwise you will get error

Answer 3

You can try with SELECT query and JOIN in CTE as follows:

with cte as
(select
    blah.column1,
    blah.column2,
    blah.column3,
    table2.column2 as t2col2
from blah
inner join table2
on blah.column1 = table2.column1)
update cte 
set t2col2= column2;