问题：
在尝试过程中还是遇到不少问题的，在此记录一下，以后再用时可以继续深入研究
1、GeoServer发布后，常常遇到这个错，度娘说是返回数据的格式问题，但是不知道怎么查。
经测试，用到case whe、Group by的都会报这个错
GeoServer 查询sql视图
标签：交互 sql int view ESS HERE UNC 数据库 视图
GeoServer 查询sql视图
OR REPLACE FUNCTION public.func_pipelength()
RETURNS TABLE(pipetype integer, pipelength double precision) AS
$BODY$
BEGIN
RETURN QUERY
select 1 as pipetype,sum(st_length(geom)) as pipelength from t_pressureline tp left join t_pressureline_type tpt on tp.pressuratingcode = tpt.id where tpt.belong = 1
union
select 2 as pipetype,sum(st_length(geom)) as pipelength from t_pressureline tp left join t_pressureline_type tpt on tp.pressuratingcode = tpt.id where tpt.belong = 2
union
select 3 as pipetype,sum(st_length(geom)) as pipelength from t_pressureline tp left join t_pressureline_type tpt on tp.pressuratingcode = tpt.id where tpt.belong = 3
union
select 0 as pipetype,sum(st_length(geom)) as pipelength from t_pressureline tp left join t_pressureline_type tpt on tp.pressuratingcode = tpt.id where tpt.belong is null;
END;