That's because it's an impossible question. Different DBMS's have varying strengths and weaknesses when use for varying purposes. Without narrowing down the use to which the DBMS is put, it's impossible to say which is "most popular".
Also, bear in mind that "most popular" and "best" are usually not the same thing.
Hi bear, I totally agree. However, i'm writing a university paper where i want to discuss how various organisations may choose one database over another for some of the reasons you mention. It would be nice to include some information on current trends thats all. Maybe i should rephrase my question to biggest market share? I *assume* that Oracle or SQL Server will be around the top with MySQL somewhere picking up the rear etc....however would just like to get my hands on a crediable survey to support this.
Quite often, the decision was made 20 years ago. Maybe it was because the user was an IBM customer, so went for DB2. Frequently, they are still using the same DBMS as they are efectively locked into it. What they might do, though, is migrate from mainframes to UNIX servers. LINUX is quite popular these days ...
I googled: "market share" ibm oracle database sybase
and came up with a couple hits. I'm sure more could be found. However, the question itself probably has no one easy answer. The answer is complicated. For example how do you define market share. Who leads market share if?
1) A vendor sells 100,000 licenses at $100 each and each database instance has one end user (a total of 100,000 users) 2) Another vendor sells 10,000 licenses at $20,000 each and these database instances have 20,000,000 end users. 3) An open source project is given away free with Linux and everyone that uses Linux gets it, but only a fraction of users that get the database actuaally use it. Because open source products are free to download, it is much harder to track their actual usage.
Vendors can spin these numbers any way they want.
Also, there are different database segments. Sybase, my company is the market leader on wallstreet, and we have the leading small footprint database. So our overall market numbers may be meaningless if you are in those 2 areas.
I suspect without being a little more specific your question has no answer.
I was particulary interested in the survey question asking developers what database servers they are currently choosing for new projects. I certainly did not expect to see SQL Server rated so highly!
I know such surveys can never truly be reflective of the current situation, or indeed take into account some of the points you and Roger above made. However, i will raise similar points that you have when discussing such matters in my paper.