No title

Oliver Dizon wrote:

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)

That seems unlikely.

Can you produce a reproducible test case?

Yours,
Laurenz Albe

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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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Oliver Dizon <johnoliver@rtzassociates.com> writes:

Hi Guys,
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'

Read up on "outer references" in SQL sub-selects. This query is entirely
legal, although it doesn't do what you want.

regards, tom lane

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Oliver Dizon <johnoliver@rtzassociates.com> writes:

Hi Guys,
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'

Read up on "outer references" in SQL sub-selects. This query is entirely
legal, although it doesn't do what you want.

regards, tom lane

It is indeed an example of outer references. I guess I should used aliases for tables in constructing queries with sub-selects to avoid this instance.

Thanks!

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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

Yea. I've realized that it's yet another example of "outer
reference". I guess I really need to read another SQL book again :-)

Thanks!

______________________
Oliver G. Dizon
Z Getcare Systems Team
RTZ Associates, Inc.
johnoliver@rtzassociates.com

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