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0 pointspaulddraper6mo ago0 comments

SQL is a declarative language so it —- by definition —- hides the execution.

Not really sure what you’re trying to argue here.

0 comments

Parent made it sound - to me - that you put an input in and hope for the best. If you understand the operators, you can quite confidently predict an output given an input.

halfcat6mo ago

> If you understand the operators

That’s the point. In an imperative language if you don’t yet understand (or make a typo, or whatever), you can just print/console.log and find out.

I’ve seen junior devs, data analysts, and LLMs spin their wheels trying to figure out why adding a join isn’t producing the output they want. I don’t think they would figure it out using SQL alone if you gave them a month.

SkiFire136mo ago

The equivalent of `print`/`console.log` in SQL would be using subqueries/CTE and run them to see the intermediate result (just like `print`/`console.log` show you intermediate results of the executions in an imperative language).

sgarland6mo ago

Then you back off, and go back to first principles. Create the minimum example of the problem, and as a sibling comment mentioned, break it down to its constituent parts and observe what happens in each.

teh_klev6mo ago

>hides the execution.

But you're not prevented from finding out how your query was executed. For example EXPLAIN (MySQL, Postgres) or query analyser for MSSQL.

crazygringo6mo ago

You missed the "performance" part.

Depending on how you write your query and how you structure your data, a query can take 0.005 seconds or 500 seconds.

SQL hiding the execution is an extremely leaky abstraction. To get the performance you need, you have to plan your possible queries in advance together with how to structure the data.

I mean, it doesn't matter if you only have 100 rows per table, but once you're dealing with multiple tables with millions of rows each it's everything.

greekrich926mo ago

If you use bubblesort instead of quicksort it will take longer as well. Knowing the language and understanding the schema solves this.

j / k navigate · click thread line to collapse

0 comments

sgarland6mo ago

Parent made it sound - to me - that you put an input in and hope for the best. If you understand the operators, you can quite confidently predict an output given an input.

halfcat6mo ago

> If you understand the operators

That’s the point. In an imperative language if you don’t yet understand (or make a typo, or whatever), you can just print/console.log and find out.

SkiFire136mo ago

sgarland6mo ago

teh_klev6mo ago

>hides the execution.

But you're not prevented from finding out how your query was executed. For example EXPLAIN (MySQL, Postgres) or query analyser for MSSQL.

crazygringo6mo ago

You missed the "performance" part.

Depending on how you write your query and how you structure your data, a query can take 0.005 seconds or 500 seconds.

SQL hiding the execution is an extremely leaky abstraction. To get the performance you need, you have to plan your possible queries in advance together with how to structure the data.

I mean, it doesn't matter if you only have 100 rows per table, but once you're dealing with multiple tables with millions of rows each it's everything.

greekrich926mo ago

If you use bubblesort instead of quicksort it will take longer as well. Knowing the language and understanding the schema solves this.

j / k navigate · click thread line to collapse