Most document- and KV-stores only support a subset of what can be expressed with SQL.
In fact, I have yet to see a feature that can not be expressed in SQL.
Thus, the advantages of using SQL are obvious:
* SQL is well understood and mature
* People already know SQL
* SQL parsers and clients are dime a dozen
* SQL lends itself reasonably well to interactive
use by humans. Much better than typing raw
javascript into a console (MongoDB) or having to write
actual code for every little data-manipulation task
(most others).
* Existing SQL-infrastructure can be leveraged.
For example your favorite ORM could easily grow an
adapter for a "NoSQL"-Db when it's just a slightly
different SQL dialect instead of a completely
distinct API.
Unlikely. How will SQL deal with low-level semantics that do not provide transactions in the way SQL-users understand them but requires the user to understand the concepts of the CAP principle? How well does SQL deal with conflicting data being returned from retrieval operation? If SQL is being used as nothing more than a small set of verbs (a la memcache) then why bother?
I certainly hope that document-store developers do not take the lazy route and prematurely converge on a standard like SQL. Fortunately it seems that few of them are particularly interested in this route and the more likely path seems to be providing multiple interfaces with RESTful HTTP, memcache, and a programmable/functional interface using JavaScript and/or the language the DB is coded in (Erlang and Java primarily.) Other possible candidates here are things like LINQ, Hive's QL, and Pig.
Unlikely. How will SQL deal with low-level semantics that do not provide transactions in the way SQL-users understand them but requires the user to understand the concepts of the CAP principle?
I'm not sure what you mean. SQL Databases have varying feature-sets already and SQL copes just fine. A "NoSQL" backend would simply be yet another type of database, lining up with e.g. MySQL and Postgres.
It's just a matter of applying the verbs (SELECT, CREATE, INSERT, UPDATE) in a meaningful way.
The individual stores could even extend the language to a degree, just like the RDBMS flavours do today. The important wins would be a common baseline (select foo from bar), a standarized way for human interaction (adhoc queries in a console are very useful) and a much easier migration path from traditional RDBMs.
How well does SQL deal with conflicting data being returned from retrieval operation?
Again I wonder what you mean?
If you're referring to versioned stores, or stores with particular semantics, then I'd imagine things like that to be simply embedded into the response. I.e. all tables returned by a select-statement could simply contain an additional column containing the tuple version. The user can then deal with that meta-data using the usual, time-tested SQL machinery (select .. where version=, group by, etc.)
Yes, this means every store needs slightly different treatment. But that's no different to how we treat RDBMs today - a common baseline with variance in the more specific features (column-types, indexes, triggers etc.).
I certainly hope that document-store developers do not take the lazy route and prematurely converge on a standard like SQL.
That's a strange wish to have as it only makes life harder for everyone. I don't see anything bad about SQL (the language) that would prevent it from taking this role.
Moreover the query language doesn't need to have ties into the underlying implementation - it's merely a common vocabulary.
SQL seems like a natural choice due to its ubiquity.
LINQ, in my book, is an ORM and operates at a different level of abstraction. Pig and HiveQL otoh are exactly what I have in mind - SQL dialects.
[Not converging on SQL] only makes life harder for everyone.
No, it makes life harder for people trying to use off-the-shelf ORMs and other RDBMS tools. I would much rather make life harder for them than make it harder for the developers of these databases.
I don't see anything bad about SQL (the language) that would prevent it from taking this role.
I, for one, do not think that it is expressive enough to cover all of the different paradigms being explored. It is based on a row/column view of the data that may not be appropriate and which may require additional hoops to be jumped through in order to get the data presentable for the assumptions that SQL makes. Who would be responsible for these transformations? IMHO it should be the end-user, but if SQL gains traction any time soon the db developers will be repeatedly browbeaten by DBAs who can't comprehend why anyone would not share their viewpoints regarding data structuring and could you please make things look like the RDBMs systems we are used to kthxbye...
Adding SQL seems to offer very little at this point except future headaches.
I, for one, do not think that it is expressive enough to cover all of the different paradigms being explored.
You are not alone with that opinion, I've seen it a couple times in similar discussions. Yet I'm missing a concrete example for a piece of functionality that can't be reasonably wrapped.
Browbeating is irrelevant in either direction. What matters for adoption is a sane interface for day-to-day use and that includes proper tooling for interactive use - an area where many of the contenders are still sorely lacking.
Good points, but SQL is 'only' a language, not a protocol. Servers still need to agree how to expose an HTTP API that could take SQL. Ideally such API would be RESTful.
I don't see that as a big problem. The queries will have to be parsed and processed inside the Database anyways. Thus the servers could simply accept SQL strings over HTTP - or any other transport protocol.
Most document- and KV-stores only support a subset of what can be expressed with SQL. In fact, I have yet to see a feature that can not be expressed in SQL.
Thus, the advantages of using SQL are obvious: