Selecting All Columns But One In Postgres

Lukas Eder shows off a BigQuery feature which you can partially implement in Postgres:

In BigQuery syntax, we could now simply write

SELECT * EXCEPT rk
FROM (...) t
WHERE rk = 1
ORDER BY first_name, last_name

Which is really quite convenient! We want to project everything, except this one column. But none of the more popular SQL databases support this syntax.

Luckily, in PostgreSQL, we can use a workaround: Nested records:

SELECT (a).*, (f).* -- Unnesting the records again
FROM ( SELECT a, -- Nesting the actor table f, -- Nesting the film table RANK() OVER (PARTITION BY actor_id ORDER BY length DESC) rk FROM film f JOIN film_actor fa USING (film_id) JOIN actor a USING (actor_id)
) t
WHERE rk = 1
ORDER BY (a).first_name, (a).last_name;

Notice how we’re no longer projecting A.* and F.* inside of the derived table T, but instead, the entire table (record). In the outer query, we have to use some slightly different syntax to unnest the record again (e.g. (A).FIRST_NAME), and we’re done.

Read the whole thing.  Lukas has a workaround for SQL Server, but I’d really like to see SELECT * EXCEPT [something] be viable syntax.  This is something I’d want to use more for ad hoc diagnostic queries, but I have one scenario where most columns on a table are narrow but then I have a big VARBINARY(MAX) (for good reason, I promise) that I almost never want to see in diagnostic queries.  I use a third-party SSMS plugin to populate all the columns and remove the one I don’t want, but it’d be nice to specify the other way because it’s so much faster to type.

Related Posts

Hooking SQL Server to Kafka

Niels Berglund has an interesting scenario for us: We see how the procedure in Code Snippet 2 takes relevant gameplay details and inserts them into the dbo.tb_GamePlay table. In our scenario, we want to stream the individual gameplay events, but we cannot alter the services which generate the gameplay. We instead decide to generate the event from the database […]

Read More

Reading and Writing CSV Files with spark-dotnet

Ed Elliott continues a series on Spark for .NET: How do you read and write CSV files using the dotnet driver for Apache Spark? I have a runnable example here:https://github.com/GoEddie/dotnet-spark-examples Specifcally:https://github.com/GoEddie/dotnet-spark-examples/tree/master/examples/split-csv The quoted links will take you straight to the code, but click through to see Ed’s commentary.

Read More

Categories

May 2018
MTWTFSS
« Apr Jun »
 123456
78910111213
14151617181920
21222324252627
28293031