Monday, March 24, 2014

A Better Query Language than SQL

SQL is a very rich and expressive language to query relational databases. But it is awkward in many aspects, and a lot of people perceive it to be evolving only slowly - even if that is not true, considering the pace of SQL standards. But the standard is one thing, the implementations another - especially in the enterprise. When we blog about SQL, we’re constantly surprised ourselves, how awesome the PostgreSQL dialect is. But often, PostgreSQL actually just implements the standard. So there is hope that we’re getting somewhere.

Nonetheless, in Leland’s article, there are a couple of ideas worth picking up. From our point of view, these are mainly:

Flexibility in ordering the SELECT clause and the table expression

In SQL, SELECT is always the first keyword. It must be expressed before the table expression. We’ve shown in a previous article that this is quite confusing for many SQL users. While the existing syntax should continue to exist, it would be good to be able to inverse the SELECT clause and the table expression.
1FROM table
2WHERE predicate
3GROUP BY columns
4SELECT columns
Remember, the table expression contains FROM, WHERE, GROUP BY clauses, as well as vendor-specific CONNECT BY clauses and others:
1<query specification> ::=
2  SELECT [ <set quantifier> ]
3    <select list> <table expression>
This language feature is already available in LINQ, by the way.

Implicit KEY JOINs

This feature is also available in jOOQ, using the ON KEY clause. Note that Sybase also supports ON KEY joins:
1from post
2key join user
3key join comment
4select *

Named projections

This is one of the features we really wish that the SQL language had. However, we wouldn’t count on specifying projections in a dedicated syntax. We had rather use an extension to the table expression syntax, allowing for a table to produce “side-tables” as such:
1from dbo.users
2with projection as (
3  firstName, lastName, phoneNumber, email
4)
5select projection.*
In the above example, projection is really nothing else than another table expression that is derived from the users table. From a SQL syntax semantics, this would be extremely powerful, because such projections would inherit all syntactic features of a regular table. We’ve blogged about this before, when we called that feature “common column expressions”.

Conclusion



Leland has lots of other ideas. He’s just at the beginning of a project that will still need a lot of refinement. The feedback he got on reddit, however, is rather good. Clearly, there is a lot of potential in creating “BQL” for SQL what
  • less is for CSS
  • Groovy is for Java
  • Xtend is for Java
  • jQuery is for JavaScript

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