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How do SQL developers go about keeping up on current techniques and trends in the SQL world? Are there any blogs, books, articles, techniques, etc that are being used to keep up to date and in the know?
There are a lot of opportunities out their for OO, procedural, and functional programmers to take part in a variety of open source projects, but it seems to me that the FOSS avenue is a bit more closed for SQL developers.
Thoughts?
Find challenging questions that test your TRANSACT-SQL knowledge ... personally I enjoy Joe Celko's SQL Puzzles and Answers.
Joe Celko's SQL Puzzles and Answers http://ecx.images-amazon.com/images/I/51DTJ099P7L._SL500_BO2,204,203,200_PIsitb-dp-500-arrow,TopRight,45,-64_OU01_AA240_SH20_.jpg
The thing about the SQL language is that it is pretty much a static target. Pretty soon you are looking at increasing your understanding of set theory and the problem domain itself rather than the details of the language.
The real meat is on either side of the language, in either the databases themselves (how to store, retrieve, and organize large data sets) or in the applications (with ORMs and such)
I skimmed the answers and apparently nobody has mentioned Stephane Faroult's work.
I strongly suggest you should consider "The Art of SQL" (http://www.amazon.com/Art-SQL-Stephane-Faroult/dp/0596008945), I found it really interesting and - amazingly enough, even fun to read.
How about http://sqlblog.com/
I improve by analyzing slow and complex queries and looking for ways to improve them. This can be done in SQL Server by analyzing the Query Plan tools and looking for bottlenecks. Also I find the Visual Quickstart Guide guide to be good for quick reference.
Joe Celko's SQL Puzzles and Answers and SQL for Smarties are the two best generic SQL books out there. Both are great sources to give you ideas for that tricky problem you used to think you needed a cursor or some client library to accomplish. For any truly interested SQL geek, these book are also pretty good for casual reading rather than as a mere desk reference. Two thumbs up.
While not a SQL Server expert, in general I find that community based events are great ways to keep up on current patterns. The underlying result of participating in a community of developers/DBAs/Marketing Pros/insert profession here is that you are learning new thought patterns and excercising critical thought. This is a great way to grow as whatever professional you are.
There aren't current techniques and trends in SQL. There's only that stuff you should already know but don't. The proper way to learn that stuff, is pain... so much pain.
Join a mailing list for the DB flavour you use...or lurk on stackoverflow ;)
Most "current" stuff is not SQL itself, but how the database stores the information, and how to retrieve it more quickly. Check out this other thread: What are some references, lessons and or best practices for SQL optimization training
The only real bleeding edge is in query planning, index structures, sort algorithms, things like that, not the SQL itself.
The fact that you asked this question is already a good sign. Avoiding complacency is "piece of advice #1". There is no substitute for writing and optimizing SQL. Practical use is the best way to stay sharp, but there is a risk of a "forest for the trees" scenario, where we tend to use what is comfortable and familiar. Trying new tactics, examining new approaches, and looking for new ways to train our brains to think about sets, SQL, relational theory, and staying on top of new developments in the particular dialects we employ are all hallmarks of good SQL developers.
There are many good blogs out there these days. I work mostly in the Microsoft arena, so I like SQLTeam.com.
Usenet is a good place to hang out and make a contribution. There are many SQL-related newsgroups. Often, you will find that working on someone else's problem helps you learn a new tactic or forces you to research a dusty corner of the language that you do not encounter every day. ISPs seem destined to shut all of the Usenet down, though, because of nefarious use, so this one may be going the way of the Dodo bird.
Also, some IRC servers have a vibrant sql channels where you can make the same sort of a difference (just take a thick skin with you).
Lastly, this very website might be another place to hang, where you can read over the answers to difficult questions, see how that might apply in your own world, practice the techniques, and internalize them. Contribute too, because seeing how others vote your solutions up or down is 100% pure honest feedback.
Of course, there are many wonderful books out there, too. Anything by Celko is a winner, and on the SQL Server side, Kalen Delaney and Ron Soukup have written some winners.
Best thing I've run into is working on other people's SQL code. Especially legacy business code. You want to test your skills against something, start changing some "voodoo code" that no one else understands. :)
Beyond that, I just try to keep an eye on changes with new releases of SQL and see if there's anything I can take advantage of.
gleam tips when using phpmyadmin
it's nice and verbose
Here is one with some interesting SSIS information.
http://blogs.conchango.com/jamiethomson/default.aspx
There is also some good information in the Wiki here:
http://wiki.lessthandot.com/index.php/Main_Page
For those who say SQL never changes, SQL Server 2005 and 2008 have some huge changes in the T-SQl that will help solve some difficult problems that were horrible to do in SQL Server 2000 and are much easier once you learn the new syntax, so yes there is stuff to keep up with.
Also performance tuning and SSIS are extremely complex subjects with much to learn.
I do find that developers who choose not to learn advanced SQL skills tend to write poorly performing SQL code and once the number of records grows in their databases, the applications they wrote tend to become glacially slow and very difficult to fix at that point. Right now I'm working with developers to fix some bad code they wrote that is causing timeouts on the site on virtually every query. Obviously, this is now an emergency and it would have been easy to write the code in a more efficeint manner at the start if the developer had better SQL skills.
I've never heard of the term "SQL developer." SQL should be a skill in your toolbox, like sorting, whatever framework you like, JavaScript, and so on. The best way to continue to improve your SQL skills to continue using it.
As a developer, and not a DBA, I keep an eye on various developer resources, and that often is DB related, but I don't specifically 'try to keep up'.
I know plenty, but I also know that there is so much more that there is to know. And in every project I have to learn something new. And every project also involves me taking a different approach to a similar task I'd encountered in the past.
Should I ever get to the stage where I think I'm doing the same things all the time, perhaps I'll make a concious effort to take specific steps. But currently, and for the foreseeable future, I'm learning organically, on-the-job, and as my projects dictate.
Reading:
Books - Celko (also read across to some Oracle-biased books)
Blogs - the above mentioned, plus SSWUG
Webinars and Conference - Best way to keep up with vendor-specific stuff like
SSIS/SSRS/SSAS
Practice:
Improving code (mine and others)
Refactoring
Mentoring/training other developers
Honestly, it's one of those things that you just get better at with time. Read as much as you can to know what's possible. Some things will take a while to really understand. I was scared off by sub queries for a long time until I pretty much had no choice but to use them.
When you get more experiance and need to do more complex things, you will just learn your way.
SqlServerCentral - great source of articles, scripts, advice
Unfortunately to access the articles you need to register (it is free though)
I guess one thing they could learn from StackOverflow is to remove login barrier
We've written a full tutorial, and you can test your SQL skills at a separate site (also created by our me, in the interests of full declaration).
SQL developers, or DBAs?
Aside from learning different dialects of SQL (Oracle, SQL Server, etc) in your day to day work, SQL doesn't actually change all that much. Sure you can bring in more advanced concepts as you develop your skills, work out where to implement stored procedures, etc, but in the end it's just SQL. The most important thing is to get your schema correct and maintainable.
Now administering the databases is a whole different thing, with a range of tools, and the database software itself getting updated every few years. Oracle at least have newsletters and websites and magazines that presumably include lots of information and examples and best practice scenarios.
To be honest, I don't see much a need for extreme SQL skills. Once I can create transactions (for DB consistency) and basic triggers (for cross-table consistency), I'm usually fine keeping program logic... in the program, and not putting it into whatever database I'm using. I've not found much depth to SQL worth investigating for a lifetime, unlike general programming, which keeps expanding in depth.
Related
I just started a new job recently and I'm trying to learn all of the bits and pieces of the database but I've never done a job like this before. It seems like it's difficult to go about it in a systematic way without some kind of in-depth documentation on everything which doesn't exist at the moment as I'm at a startup. It's in PostgreSQL, I'm not sure what other information you guys'll need to help me out. I'm learning SQL and have plenty of resources I can use to improve there, but are there any exercises or ways of studying the database that I can use to better familiarize myself with the underlying logic and what all of the individual tables/columns/views are and how they relate. If there's any other information that would help you to help me then just let me know and I'll provide it as best I can.
I use DataGrip from JetBrains to explore databases and for creating queries. DataGrip also has a handy tool to diagram relationships between tables. Unfortunately, the tool is not free, but it comes in handy for sure.
There are many great database tools available online; DataGrip just happens to be the one I use most.
Also, there is a great post on Quora with plenty of links to learning resources.
Good luck with your new job.
DataGrip's Diagram tool
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If someone knew little about databases and wanted to learn about them from scratch, which database would you recommend learning with and why?
MySQL seems ubiquitous, but are there others that are more modern that have learned lessons from the past, or others that are simply nicer or more logical to work with?
Universal compatibility/libraries is not a big concern, unless it is something truly obscure. Mac (Unix) compatibility is a must.
If you just want to be learning the SQL language, and not database administration, I would recommend working with SQLite. If you're on a Mac, it should already be installed. It is a much simpler system than most RDBMSes; there is no server to set up, and client to connect to the server. There are no directories of cryptic files, or anything of the sort. To get started, you can just type:
sqlite3 mydatabase.db
And start working with it. It's so much lighter weight and easier to set up and use than the other database systems that I think it's a good choice for a beginner.
Now, SQLite is a fairly small and lightweight language. If you need be getting into any kind of really complex queries and data mining, I would recommend PostgreSQL. It has a fairly advanced query optimizer, and a pretty long list of SQL features.
And if you want to learn a database as something to use for back-end storage for web programming or something of the sort, MySQL is what I'd choose. It's ubiquitous, supported by almost any web host, and it's pretty fast for very simple queries and updates, which is generally what you need for a web system. It has some real gotchas to avoid when setting it up; you have to choose between several different storage engines, and it can take a lot of work to convince it to actually work with Unicode data. But it's good to learn mostly for its ubiquity.
From what I've seen (at least on the web), MySQL and PostgreSQL are the most ubiquitous free database systems. If you're considering learning one of them, check this comparison out.
You may also want to consider learning SQLite, a "self-contained, embeddable, zero-configuration SQL database engine." It's really easy to get up and going, stored in a single file, and as its description says, has no complicated configuration. SQLite has proved enormously popular as a persistent data store for local apps on the desktop/iPhone. If you're going down this route on a Mac/iPhone, you may also want to check out Core Data, which is an abstraction layer Apple developed on top of SQLite(but can work with pretty much any DB), to simplify working with a database. As a bonus, Core Data includes a nice GUI for forming relationships and entities. You can check out this tutorial for more information.
If you really, truly, want to "learn from scratch", then theory is the first thing to learn. And that means : NOT products, not any. Not DB2, not MySQL, not oracle, not any-of-them.
Hugh Darwen has a freely available e-book entitled "An Introduction to Relational Database Theory". The material is quite "accessible" and quite unlike most other theory textbooks. It's also the accompanying textbook for his university course on database technology.
Chris Date has several books, of which "Introduction to database systems" is the most comprehensive, also the standard textbook in the field, but maybe a little too abstract for some.
If you think that all you need is "just to know a product" and that you can do equally well "without all that theory", then in that case, please disregard this response, because the wording of your question is dishonest.
Sad thing about databases is that each and every one works bit differently. I would most likely pick MySQL first and play with it a bit. Then get PostgreSQL and do the same.
If you need to use databases in corporate environment then I would aim to test also Oracle and SQL Server which both have express versions that can be installed free for yourself.
http://www.microsoft.com/express/sql/download/
http://www.oracle.com/technology/software/products/database/index.html
At start all databases are more or less confusing but I would pick MySQL as first because it can do most of the basic functionalities and has a lot of help available.
I'd go with mysql. It's easy to setup, easy to mess around with via with mysql client, and it's well documented. If you're just starting out, you probably won't need most of the features offered by other databases, like stored procedures and the like.
First of all, MySQL is both ubiquitous and modern.
ANSI SQL is more or less the same in all RDBMs, so you can learn any of them and you'll be good.
Once you've mastered ANSI SQL, then all you've got left is the localized solutions for each one of them, which won't be portable to other systems - and so, totally discouraged to use, unless they simplify your tasks in a way justifying it.
MySQL, PostgreSQL, SQLite - pick one. PostgreSQL is more like Oracle, and in my opinion a bit more mature. It's had stored procedures, triggers, and referential integrity longer than MySQL has. I'll admit that I have both installed, but I use MySQL more often because it's quick and easy.
But do be aware that non-SQL alternatives are out there and growing in importance. BigTable, object databases like db4o, are worth being aware of. "No SQL" is out there.
If you are just getting your feet wet, MYSQL is a great one to start with. Easy install on any platform, great community support and lots of free tools to work with (SQLYog is a favorite of mine).
I agree that theory is very important. Depending on how you learn best, digging in and tinkering may be the thing to do before you try to absorb 40 years of thought on relational systems.
Codd and Date are legends in the field and can help you understand the broader points of relational theory, but are hard to absorb before you have context for the topic.
If you are looking for more pragmatic/immediate guidance, I'd suggest a book like "Databases for Mere Mortals" and anything written by Joe Celko.
Once you get comfortable with the basics, there are lots of other platforms to explore as well. As mentioned above, SQLLite and PostGres are two other great choices for the Mac OS.
If you want to learn SQL : the best way is to choose database who implement more features of the SQL standard. So I would recommand Firebird or PostgreSQL
I might be "sidetracking" a bit with this answer, but I think we're in the same situation!
Check out the "The Manga Guide to Databases"! I haven't read it myself yet, but it's on the way in the mail as we speak! I've heard good things about it from friends and colleges, and it's got some good reviews as well. Albeit a bit "controversial," it's supposed to be a fun and surprisingly in-depth introduction to fundamental techniques and principles!
Alex wrote: "Reading a textbook without incrementally testing your knowledge on an actual database is not going to produce good results for the majority of people."
My book and my university course both use Dave Vooorhis's Rel for that very purpose.
Hugh
A database in the cloud: Amazon EC2, Google App Engine or Microsoft Azure
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Why did object oriented databases fail?
I find it astonishing that:
foo bar = new foo();
bar.saveToDatabase();
Lost to:
foo bar = new foo();
/* write complicated code to extract stuff from foo */
/* write complicated code to write stuff to database */
Related questions:
Are Object oriented databases still
in use?
Object Oriented vs Relational
Databases
Why have object oriented databases not been successful (yet)?
Probably because of their coupling with specific programming languages.
First, I don't believe they have "failed" entirely. There are still some around, and they're still used by a couple of companies, as far as I know.
anyway, probably because a lot of the data we want to store in a database is relational in nature.
The problem is that while yes, OO databases are easier to integrate into OO programming languages, relational databases make it easier to define queries and, well, relations between the data stored. Which is often the complicated part.
I have been using db4o (an object oriented database) lately on my personal pet projects, just because it is so quick to set up & get going. No need with the itty, gritty details.
That aside, as I see it, the main reasons why they haven't become popular are:
Reporting is more difficult on object oriented databases. Related to this, it is also easier to manually look into the actual data in a relational database.
Microsoft and Oracle base so much of their business on relational databases.
Lots of businesses already have relational databases in place.
The IT departments often have relational database expertise.
And, as Jan Aagaard, have pointed out, lately it is because the problem have been solved in a different way, giving programmers the object oriented feel even though they program against a relational database.
There are countless numbers of existing applications out there storing their data in relational databases. This data is the lifeblood of those companies. They have collectively invested huge amounts in storing, maintaining and reporting on this data. The cost and risk of moving this priceless information into a fundamentally different environment is extremely high.
Now consider that ORM tools can map modern application data structures into traditional relational models, and you remove pretty much any incentive to migrate to OODBMS. They provide a low-risk alternative to a very costly high risk migration.
Because, as much as ODBMS advertisements were laden with derogatory language about ORM systems, it wasn't that hard to make ORMs do the job, and without all the various hits taken in switching to a pure ODBMS.
What actually happened is that your first code sample won, it just happens to be on a RDBMS persistence layer.
I think it is because the problem was solved differently. You might be using a relational database behind the scenes when you are coding in Ruby on Rails or LINQ to SQL, but it feels like you are working with objects.
Very subjective, but a few reasons come to mind:
Performance has not been as good as relational databases (or at least that's the perception)
Again with performance - relational databases allow you to do things like denormalizing data to further improve performance.
Legacy support for all the non-OO apps that need to access the data.
I think a lot of your answer lies in the "Why we abandoned Object Databases" answer of "Object Oriented vs Relational Databases".
As far as your example goes, it doesn't have to be that way. Linq to SQL is actually a quite nice basic layer over a DBMS, and Linq to Entities (v2 -- v1 sucked) will be pretty cool too. (N)Hibernate has been solving the problem you're having for years now using RDBMSes.
So I guess my answer to you is that O/R mappers are getting to the point where they solve your problem nicely, and you don't need an ODBMS to get what you need.
They will succeed some day. They are future.
Looking back to software technologies in history, the trend is sacrificing performance to reduce complexity (Assembly => C => C++ => .NET). An application which takes 30 minutes to code now, some days in past took a month.
ORMs are right answer to wrong question. Currently, they are the choice, since they make life easier in the absence of a better solution. But they cannot handle the level of complexity they aimed to. "Problems cannot be solved by the same level of thinking that created them." A.E
As others mentioned relational databases are heavily used and relied and replacing them forces a lot of risks. Look the interval between SQL versions and the major changes between these versions and other Microsoft products (conservative approach, which is necessary here). Also I'll add the following items:
Current approach still works. You may argue it will work forever (we
can code assembly yet), but here I mean it doesn't
work logically when, the AVERAGE level of projects complexity and
the time to develop them on relational databases rings the bell.
Major companies did not involved seriously. When the market signals, they do.
The problem is not well-defined yet. Unfortunately current failures help.
It need some improvements in other sciences (QC, AI) rather than
computer. Storing and querying multidimensional data on flat
infrastructure and without enough smartness for self-organizing are
the top obstacles at the theoretic level.
Why not?
I guess they were a solution to a problem nobody was having, or not having enough to pay for it.
Further, OOP and set-based programming are not always very comptatble.
Personally, when I started reading about OO databases, I couldn't help but think "Boy, I hope I never have to work on one of those, update 1 million rows out of a 6 million row table and then make sure all appropriate records in other tables get updated as well"
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I'm running into Db performance issues with an OTLP project I'm working on. Another developer and I have reached the end of our accumulated performance knowledge and seek out an individual to join the team to help us speed up our application.
For some background we've done schema changes to denormalize pieces of the data, optimized every query, ran multiple database tuning advisers to get our indexes just right, tuned MSSql's server options.
We don't need somebody to come in and tell us joins can be slow and what deadlocking is, we need somebody who knows what to do after exhausting all the steps listed above.
Anybody have any tips or experiences hiring OLTP DBA's to share? What kind of questions can we ask the DBA during the interview process?
Its an odd situation to be in, we know we need somebody who knows more than the current team, but we don't know what questions to ask because we don't know what the next steps are. Does that make sense?
Ok, this tells me something:
For some background we've done schema changes to denormalize pieces of the data, optimized every query, ran multiple database tuning advisers to get our indexes just right, tuned MSSql's server options.
You've already matched or exceeded what 90% of people who call themselves DBAs will be able to do.
The problem is that a lot of DBAs aren't really programmers, they are more on the system administration side of things. You need a DBA programmer who is not only really good at TSQL, but who knows your other programming language(s) as well.
I spend a significant portion of my time on database tuning issues like this, and the solution often involves significant redesigns all the way from the front end back to the database schema. You can't solve these problems in isolation, and without complete control (and total understanding) of the entire architecture, you'll never get the performance you need.
You might be the best person for the job, and it might be smarter for you to hire somebody to take busy work off your plate so you can concentrate on the OLTP performance problems.
You have to be vary careful here, you can end up hiring a Guru DBA, have him improve the database performance significantly and still have issues with your application that are rooted in its architecture.
A few ideas:
Take the most complex query you optimized give it to the candidate DBA with QA and get him/her to optimise it again. Have them describe what they did and how they did it.
Make sure this person understands hardware, when you would use multiple filegroups, raid arrays, data partitioning, 64 vs 32 bit performance etc...
Look for someone who also has some software architecture background.
Ask them a few harder SQL server questions eg. What is the OVER statement? Are GUIDs good primary keys and why, is int identity preferable?
De-tune your DB back a little to before your own optimization and give it to them. See if they can tune it to perform as good or better compared to the changes you made.
Ask why they chose that technique.
Take up references and find out about the environments they've come from which are most likely to match your own.
A good DBA will be able to tell you in the interview at a high level what steps they would take next. You should pay more attention to the thought processes here, rather than the solution to the problem. When the DBA has given some solutions, go back and quiz them and ask them why the problem should be solved in those ways.
This method will very quickly distinguish the men from the boys, as it were.
How close are you to the max performance of the db? It is very easy to create an OLTP problem that is unsolvable with this technology. As Eric said, total architecture redesign might be in order. More ram, just add more ram :)
Certainly without seeing the database it is hard to say what could be the best way to optimize. Given what you have done, likely you need to hire a database designer - one with experience designing and tuning databases in the size range that you have. In asking how they would approach the problem see if the interviewer would look at first the poorly performing queries and run profiler to see what is happening and to identify them. The person should be able to answer specific questions on parameter sniffing and how to avoid it, what are the methods that can be used to avoid cursors, why do statistics need to be updated, what makes a query saregable. There are some common things that I would look at in performance tuning. Is the network maxed out (Sometimes it isn't the database), is the overall design poorly thought out, are you using SQl code that in general performs badly? If all your searches allow a wildcard as the first character for instance, it isn't even possible to get them to be fast. If your joins are on multi-column natural keys, they are slower than they should be. Are you storing more than one piece of information in a field causing lots of manipulation to get data back out? Are you using cursors? Are you using functions? Are you reusing code when you shouldn't be? Are you always returning the minimum information needed? Are you closing connections? Are you getting deadlocks? Are your table rows too wide? Do you have too many records in particular tables (purging old records or putting them to an archive database can make a huge difference)? How much of your code is row oriented and not set oriented? These are examples of the kinds of things an experienced database person would look at and thus the kinds of things they should talk about in the interview.
Some bad code examples (you know what you have already optimized) can give you a good idea as to their approach to how they would tune. YOu want someone who is methodical and has depth of SQL knowledge.
There are some good books on performance tuning - I would suggest getting them and getting familar with them before interviewing.
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Modern database systems today come with loads of features. And you would agree with me that to learn one database you must unlearn the concepts you learned in another database. For example, each database would implement locking differently than others. So to carry the concepts of one database to another would be a recipe for failure. And there could be other examples where two databases would perform very very differently.
So while developing the database driven systems should the programmers need to know the database in detail so that they code for performance? I don't think it would be appropriate to have the DBA called for performance later as his job is to only maintain the database and help out the developer in case of an emergency but not on a regular basis.
What do you think should be the extent the developer needs to gain an insight into the database?
I think these are the most important things (from most important to least, IMO):
SQL (obviously) - It helps to know how to at least do basic queries, aggregates (sum(), etc), and inner joins
Normalization - DB design skills are an major requirement
Locking Model/MVCC - Its nice to have at least a basic grasp of how your databases manage row locking (or use MVCC to accomplish similar goals with optimistic locking)
ACID compliance, Txns - Please know how these work and interact
Indexing - While I don't think that you need to be an expert in tablespaces, placing data on separate drives for optimal performance, and other minutiae, it does help to have a high level knowledge of how index scans work vs. tablescans. It also helps to be able to read a query plan and understand why it might be choosing one over the other.
Basic Tools - You'll probably find yourself wanting to copy production data to a test environment at some point, so knowing the basics of how to restore/backup your database will be important.
Fortunately, there are some great FOSS and free commercial databases out there today that can be used to learn quite a bit about db fundamentals.
I think a developer should have a fairly good grasp of how their database system works, not matter which one it is. When making design and architecture decisions, they need to understand the possible implications when it comes to the database.
Personally, I think you should know how databases work as well as the relational model and the rhetoric behind it, including all forms of normalization (even though I rarely see a need to go beyond third normal form). The core concepts of the relational model do not change from relational database to relational database - implementation may, but so what?
Developers that don't understand the rationale behind database normalization, indexes, etc. are going to suffer if they ever work on a non-trivial project.
I think it really depends on your job. If you are a developer in a large company with dedicated DBAs then maybe you don't need to know much, but if you are in a small company then it may be really helpful knowing more about databases. In small companies you may wear more than one hat.
It cannot hurt to know more in any situation.
It certainly can't hurt to be familiar with relational database theory, and have a good working knowledge of the standard SQL syntax, as well as knowing what stored procedures, triggers, views, and indexes are. Obviously it's not terribly important to learn the database-specific extensions to SQL (T-SQL, PL/SQL, etc) until you start working with that database.
I think it's important to have a basic understand of databses when developing database applications just like it's important to have an understanding of the hardware your your software runs on. You don't have to be an expert, but you shouldn't be totally ignorant of anything your software interacts with.
That said, you probably shouldn't need to do much SQL as an application developer. Most of the interaction with the database should be done through stored procedures developed by the DBA, I'm not a big fan of including SQL code in your application code. If your queries are in stored procedures, then the DBA can change the implementation of the stored procedure, or even the database schema, and so long as the result is the same it doesn't require any changes to your application code.
If you are uncertain about how to best access the database you should be using tried and tested solutions like the application blocks from Microsoft - http://msdn.microsoft.com/en-us/library/cc309504.aspx. They can also prove helpful to you by examining how that code is implemented.
Basic things about Sql queries are must. then you can develop simple system. but when you are going to implement Complex systems you should know Normalization, Procedures, Functions, etc.