SQL Server 2008 Spatial, PostgreSQL/PostGIS 1.3
General Overview
FeatureSQL Server 2008 (RC0)MySQL 5.1/6PostgreSQL 8.3/PostGIS 1.3/1.4
OS
Windows XP, Windows Vista, Windows 2003, Windows 2008
Windows XP, Windows Vista, (haven't tested on 2008), Linux, Unix, Mac
Windows 2000+ (including Vista and 2003, haven't tested on 2008), Linux, Unix, Mac
Licensing
Commercial - Closed Source, Various levels of features based on version, Express version has full spatial support but limitation on database size and only use one processor.
Commercial Open Source (COSS), some parts GPL. Here is an interesting blog entry on the subject MySQL free software but not Open Source. The comments are actually much more informative than the article itself.
FLOSS (PostgreSQL is BSD, PostGIS is GPL Open Source - you can use for commercial apps but if you make changes to the core libraries of PostGIS, you need to give that back to the community)
Free GIS Data Loaders
shp dataloader for SQL Server 2008 developed by Morten Nielsen (doesn't yet work with RC0)
OGR2OGR, shp2mysql.pl script
included shp2pgsql, OGR2OGR, QuantumGIS SPIT, SHP loader for PostGIS also developed by Morten using SharpMap.NET various others
Commercial GIS Data Loaders
Manifold, Safe FME Objects, ESRI ArcGIS 9.3 (in a later service pack)
Safe FME Objects
Manifold, FME Objects, ESRI ArcGIS 9.3
Application drivers available specifically for spatial component
? Not yet - SharpMap.NET eventually and probably built into new ADO.NET 3.5+
GDAL C++, SharpMap via OGR, AutoCAD FDO
SharpMap.Net, JDBC postgis.jar included with postgis, JTS etc. tons for Java, GDAL C++, AutoCad FDO beta support
Free Object/Relational Mapping
NHibernateSpatial (this is a .NET object relational spatial mapper) - beta support
Hibernate Spatial - this is a java object relational mapper
NHibernateSpatial and HibernateSpatial
Free Desktop Viewers and Editors
Will be built into SQL Manager, but not available in RC0 and only useful for viewing
GvSig
OpenJump, QuantumGIS, GvSig, uDig
相关文档：
几个删除重复记录的SQL语句
2009-03-02 10:08
比如现在有一人员表 （表名：peosons）
若想将姓名、身份证号、住址这三个字段完全相同的记录查询出来
select p1.* from persons p1,persons p2 where p1.id<>p2.id &nb ......
做个矩阵，其实就是个二维数组，关键是要从数据库里调些数据，sql语句不熟练，就边学边用，同步地记些笔记，方便查阅
关于distinct和order by 发了个帖子（第一次哦）
首帖：
用的是oracle的数据库
目的是想选出唯一的userid（原有重复值）,并且按照filepos排序（原filepos是1，2，3.。。不重复的序号）
......
SQLServer和Oracle是大家经常用到的数据库，在此感谢作者总结出这些常用函数以供大家参考。
数学函数：
1.绝对值
S:SELECT abs(-1) value
O:SELECT abs(-1) value from dual
2.取整(大)
S:SELECT ceiling(-1.001) value
O:SELECT ceil(-1.001) value from dual
3.取整（小） ......
ORDER BY 排序
ASC 升序(默认)
DESC 降序
select * from s_emp order by dept_id , salary desc
部门号升序，工资降序
关键字distinct也会触发排序操作。
select * from employee order by 1; //按第一字段排序
NULL被认为无穷大。order by 可以跟别名。
select table_name ......
我们使用oracle的人都知道可以通过rownum伪列得到查询结果序列前面的指定的行，为了下面更好的进行说明问题，我们先来创建一个数据表table1：
create table table1
(AAA integer primary key,
BBB varchar(30));
然后在table1中插入9条数据：
insert into table1 values (8, 'good');
insert into table1 values (7 ......
