Oliver Dizon schrieb am 27.01.2015 um 11:46:
> I hope I'm in the right place to throw this. I just want to ask the reason 
> behind this weird scenario.
> 
> All records were deleted in a table even if the subquery in the where clause 
> has a missing a column.
> 
> --from a certain script where table_id is not yet existing on table_sample
> 
> delete from main_table_sample where table_id in (select table_id from 
> table_sample);
> 
> Im expecting that postgres will return an ERROR message like
> 'column "table_id" does not exist on table table_sample'
> 
> But it did not returned any error and deleted all the records instead.
> 
> Version: psql (8.4.9, server 9.2.5)

No, this is correct and complies with the SQL standard. If you reference a 
column in a sub-select that is available in the outer query but not in the 
sub-select, then it's automatically a reference to the column from the outer 
query. 

So in your query, the column "table_id" in the sub-query references the 
main_table_sample.table_id.

I agree this is confusing, but it's the way it was specified in the SQL 
standard.

Thomas



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