PRQL, Pipelined Relational Query Language

Re:PRQL, Pipelined Relational Query Language by jdmichal on Tuesday July 25, 2023 @04:15PM (#36868710)

I've had two real gripes with SQL. The rest of it has been, as you said, pretty good.

Complaint 1: Not being able to use selected columns later in the same select.

    SELECT
        gnarly_calculation AS some_value,
        some_value * 2 AS some_value_doubled

Instead:

    SELECT
        subquery.*,
        some_value * 2 AS some_value_doubled
    FROM (
        gnarly_calculation AS some_value
    ) AS subquery

Complaint 2: Not being able to specify all columns except. This combines with the above, where I have to pull some intermediate calculations forward from a subquery, but I don't need them in the final output. So I have to then enumerate all the output columns that I actually want, instead of being able to say something like `* EXCEPT some_value`.

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Re:PRQL, Pipelined Relational Query Language by snthpy on Tuesday July 25, 2023 @05:23PM (#36869812)

PRQL fixes this.

(Disclaimer: I'm a PRQL contributor.)

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Re:PRQL, Pipelined Relational Query Language by zX41ZdbW on Tuesday July 25, 2023 @05:34PM (#36869896)

Not only PQRL fixes this. It has been allowed in ClickHouse's SQL since its inception.

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Re:PRQL, Pipelined Relational Query Language by snthpy on Tuesday July 25, 2023 @05:56PM (#36870160)

That's awesome! ClickHouse is a great system by all accounts and I've been meaning to try out ClickHouse Local.

I'm more familiar with DuckDB and they've also been doing some great innovation on the SQL front. I don't know offhand if they can also do the forward referencing thing but they allow putting the FROM first and having GROUP BY ALL etc..

It's great to see all this innovation happening in the SQL and Query Language space more generally at the moment.

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Re:PRQL, Pipelined Relational Query Language by zX41ZdbW on Tuesday July 25, 2023 @06:19PM (#36870437)

It is strange to hear about innovation in DuckDB - I see that they are gradually re-implementing the stuff already existing in ClickHouse. Sometimes they do a better job at promoting it.

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Re:PRQL, Pipelined Relational Query Language by snthpy on Tuesday July 25, 2023 @06:41PM (#36870717)

That's probably true but the big differentiator was that DuckDB can run in your python process so there's very low fiction to adopt it.

My impression of ClickHouse was that it was more like postgresql in that regard, i.e. OLAP : OLTP as ClickHouse : Postgres as DuckDB : SQLite.

clickhouse-local may have closed the gap on that though. Can you embed it in Python as a library?

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Re:PRQL, Pipelined Relational Query Language by zX41ZdbW on Tuesday July 25, 2023 @07:16PM (#36871042)

> Can you embed it in Python as a library?

https://github.com/chdb-io/chdb

    pip install chdb

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Re:PRQL, Pipelined Relational Query Language by glogla on Wednesday July 26, 2023 @05:40AM (#36875092)

They also do bunch of stuff that ClickHouse can't do, like correlated subqueries [1] or recursive CTEs.

I kinda wish for a database with ClickHouse storage, because MergeTree seems incredibly good at what it does and DuckDB optimizer, because the ClickHouse one has a lot of limitations.

[1]: https://duckdb.org/2023/05/26/correlated-subqueries-in-sql.h...

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Re:PRQL, Pipelined Relational Query Language by zX41ZdbW on Tuesday July 25, 2023 @05:33PM (#36869885)

Both complaints are resolved by ClickHouse.

This video also covers many other advantages of ClickHouse's SQL dialect: https://www.youtube.com/watch?v=zhrOYQpgvkk

Some may find your first complaint questionable... But I specifically designed ClickHouse SQL to allow aliases to be used and referenced in every part of SQL query.

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Re:PRQL, Pipelined Relational Query Language by jdmichal on Tuesday July 25, 2023 @10:00PM (#36872264)

So unsurprisingly based on my gripes, we are an OLAP shop. I've never heard of ClickHouse before, and I'll be looking into it. We're doing OK on PostgreSQL, but just OK. A lot of learning and unlearning.

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Re:PRQL, Pipelined Relational Query Language by AtNightWeCode on Wednesday July 26, 2023 @02:43AM (#36873890)

Don't use *. It is a common source for all kinds of problems. Many query langs does not support it at all for that reason.

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Re:PRQL, Pipelined Relational Query Language by jdmichal on Wednesday July 26, 2023 @12:07PM (#36880089)

I'm quite aware of your advice regarding using `` against table. However, I'm talking about using `` against subqueries and CTEs where the pieces of the table have already been extracted.

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Re:PRQL, Pipelined Relational Query Language by jdmichal on Wednesday July 26, 2023 @03:26PM (#36883503)

This is supposed to read:

I'm quite aware of your advice regarding using `*` against tables. However, I'm talking about using `*` against subqueries and CTEs where the pieces of the table have already been extracted.

I was unable to edit this earlier due to HN being unavailable after I realized the formatter mangled it.

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