Which are the SQL improvements you are waiting for?

Question

Dealing with SQL shows us some limitations and gives us an opportunity to imagine what could be.

Which improvements to SQL are you waiting for? Which would you put on t

Answer 1

A decent way of walking a tree with hierarchical data. Oracle has CONNECT BY but the simple and common structure of storing an object and a self-referential join back to the table for 'parent' is hard to query in a natural way.

Answer 2

On my wish list is a database supporting sub-queries in CHECK-constraints, without having to rely on materialized view tricks. And a database which supports the SQL standard's "assertions", i.e. constraints which may span more than one table.

Something else: A metadata-related function which would return the possible values of a given column, if the set of possible values is low. I.e., if a column has a foreign key to another column, it would return the existing values in the column being referred to. Of if the column has a CHECK-constraint like "CHECK foo IN(1,2,3)", it would return 1,2,3. This would make it easier to create GUI elements based on a table schema: If the function returned a list of two values, the programmer could decide that a radio button widget would be relevant - or if the function returned - e.g. - 10 values, the application showed a dropdown-widget instead. Etc.

Answer 3

WITH clause for other statements other than SELECT, it means for UPDATE and DELETE.

For instance:

WITH table as (
  SELECT ...
)
DELETE from table2 where not exists (SELECT ...)

Answer 4

Support in SQL to specify if you want your query plan to be optimized to return the first rows quickly, or all rows quickly.

Oracle has the concept of FIRST_ROWS hint, but a standard approach in the language would be useful.

Answer 5

Check constraints with subqueries, I mean something like:

CHECK ( 1 > (SELECT COUNT(*) FROM TABLE WHERE A = COLUMN))

Answer 6

Implicit joins or what it should be called (That is, predefined views bound to the table definition)

SELECT CUSTOMERID, SUM(C.ORDERS.LINES.VALUE) FROM CUSTOMER C

A redesign of the whole GROUP BY thing so that every expression in the SELECT clause doesn't have to be repeated in the GROUP BY clause

Some support for let expressions or otherwise more legal places to use an alias, a bit related to the GROUP BY thing, but I find other times what I just hate Oracle for forcing me to use an outer select just to reference a big expression by alias.