2005年IDC调查的RDBMS市场份额:     2008年IDC调查的Data Warehouse市场份额:   2008年做的未来dbms安装部署计划调查:     2008 rdbms market share:     Worldwide RDBMS Product Revenue by Top 10 Vendor and Operating Environment, 2009:   根据IDC以往的调查，2006年关系型数据库的市场总额为167亿美元，2007年为188亿美元。 大量报告显示Oracle仍维持着RDBMS市场的龙头老大地位，当然这种领导优势并不显著。 
Analyzing the RDBMS Market in 2009
The RDBMS market, as reported in Worldwide Database Management Systems 2009 Vendor Shares (IDC #223912, June 2010),
grew slightly in 2009, to $20.6 billion, but license revenue actually declined a little.
Vendors took in just over $11 billion in software license revenue.
This revenue, broken down by vendor and operating environment, is shown in Table 1.
Since maintenance revenue is largely driven by past purchases, it tends to resist the bumps
caused by shifting economic conditions. Although some customers deferred or negotiated a reduction
in their maintenance contacts due to the economic crisis and its consequent tight IT budgets,
that revenue category showed some growth.
By contrast, decisions to put off database projects and upgrades hurt RDBMS license sales.

The top 3 vendors continue to well outpace the rest of the market, as indicated in Table 2,
but Microsoft has overtaken IBM in terms of license revenue and is creeping ever closer to Oracle.
Oracle remains the dominant RDBMS vendor, with 31.8% of RDBMS license revenue in 2009.

Table 3 shows the RDBMS market license revenue broken out by operating environment.
Figure 1 shows the same information graphically. Although Windows was knocked off its strong growth track,
it was, at least, in positive territory. All other operating environments showed a decline.
For a detailed discussion of the vendors and their strategies,
see Worldwide Database Management Systems 2009 Vendor Shares (IDC #223912, June 2010).