7 ms·

create table x as (select * from person); select name from x where ...; there you go, just configure your editor to display "create table x" as "declare x =

• alphanumeric0 4y ago
  What if I wrote a very long, complicated query that I'd like to test against different tables (like test tables), and let's say I can't use stored functions or procedures. How could I pass different tables to my query?
  • dventimi 4y ago
    If you can't use stored procedures which are good for this very case, many databases offer dynamic SQL. That might work in some cases.
    • alphanumeric0 4y ago
      That's a good point. This would rule out SQLite for me.
    • mr_toad 4y ago
      Dynamic SQL isn’t SQL, and it’s not relational. It’s no different from using a language like Python to generate SQL queries.
      • dventimi 4y ago
        It's a little different. Anyway, this is under the constraint "no stored procedures."
  • adeelk93 4y ago
    Check out dbt - it's a great tool for organizing queries and solving such patterns
  • chrstr 4y ago
    CREATE TABLE data_a AS (SELECT 'a' AS test_case, 1 AS value); CREATE TABLE data_b AS (SELECT 'b' AS test_case, 2 AS value); CREATE VIEW data AS (SELECT * FROM data_a UNION ALL SELECT * FROM data_b); CREATE VIEW complicated_query AS (SELECT test_case, value+1 FROM data); SELECT * FROM complicated_query WHERE test_case = 'a'; SELECT * FROM complicated_query WHERE test_case = 'b';
    • alphanumeric0 4y ago
      Nice, that is what I was looking for. Of course, it'd need to point to production data as well, so maybe test_case is null, in that case: CREATE TABLE data_a AS (SELECT 'a' AS test_case, 1 AS value); CREATE TABLE data_b AS (SELECT 'b' AS test_case, 2 AS value); CREATE TABLE data_prod AS (SELECT NULL AS test_case, prod_table.value FROM prod_table); CREATE VIEW data AS (SELECT * FROM data_a UNION ALL SELECT * FROM data_b UNION ALL SELECT * FROM data_prod); CREATE VIEW complicated_query AS (SELECT test_case, value+1 FROM data); -- when testing SELECT * FROM complicated_query WHERE test_case = 'a'; SELECT * FROM complicated_query WHERE test_case = 'b'; -- when in 'production' SELECT * FROM complicated_query WHERE test_case IS NULL;
    • naasking 4y ago
      You just reinvented defunctionalization, which is a transformation from a domain that has first-class values to a domain where support is only second-class. Defunctionalization is typically used in programming languages to simulate first-class functions in languages where functions are only second-class citizens, like C and Pascal. This perfectly illustrates my point. You had to manually defunctionalize your data model and queries to support what I'm saying should be inherently part of SQL.
      • CRConrad 4y ago
        > languages where functions are only second-class citizens, like C and Pascal. 1) Only if you define Pascal as only Wirth's very first version. That changed almost immediately. 2) Only if you refuse to equate “pointer to function” with “function”. Which in C, where “everything is a pointer” (a bit like in Unix Linux “everything is a file”), seems rather silly.
  • Foobar8568 4y ago
    TVF ( Table-Valued Function) with Cross apply.
• naasking 4y ago
  You're still not getting it. First-class status means that anywhere a value or variable can be used, a query or table should also be able to appear, and vice versa. This means a table or query can appear as a return type, a parameter to a stored procedure or query, a variable, and so on. SQL just does not have this, it instead has 15 different second class ways to handle tables and queries that try to make up for the fact that they are not first-class values. These include CTEs, table valued functions, views, etc.
  • mr_toad 4y ago
    > You're still not getting it. First-class status means that anywhere a value or variable can be used, a query or table should also be able to appear, and vice versa. This means a table or query can appear as a return type, a parameter to a stored procedure or query, a variable, and so on. I doubt you could implement a query planner that would cope with that degree of flexibility. Which means you’d be forced to deal with the mechanics of the query, pushing you away from declarative SQL and into procedural and functional programming. At which point you might as well ditch SQL anyway.
    • naasking 4y ago
      Without these features, people have to resort to dynamically generated SQL queries in procedural or functional languages, which is much worse! SQL has also become significantly more complicated by adding all sorts of second-class features to get around this composability limitation (CTEs, table valued functions, views, etc.). Besides, I don't think it would be as bad as you say. You can approach it as a simple template expansion into flat SQL queries except where a data dependency occurs, at which point template expansion proceeds in stages, one for each dependency. LINQ on .NET provides most of the composability I'm talking about, although it has a few limitations as well. Still worlds better than raw SQL.
  • pgwhalen 4y ago
    Usually I balk at the idea of of someone describing a language feature as “first class” because it seems to wishy washy. But in this thread you’ve shown me that maybe the best definition is through “proof by negation,” by patiently responding to arguments and demonstrating why a certain usage and the ensuing restriction around it means it is not first class. Bravo!