Question

我有一些要在R环境中调用的PostgreSQL / PostGIS tablefunc查询。有什么方法可以执行此操作？

Ex：

dbGetQuery(con, "SELECT * FROM CROSSTAB(
'SELECT factor1, factor2, ROUND(SUM(ST_AREA(geom))::numeric, 3) FROM table GROUP BY factor1, factor2 ORDER BY 1,2',
'SELECT factor2 FROM table GROUP BY factor2 ORDER BY factor2 '
) AS ct("factor1" varchar, "factor2value1" varchar, "factor2value2" varchar, "factor2value3" varchar)
")

Answer 1

如果您成功连接到Postgres，则任何兼容的Postgres查询都可以使用。因此，如果一条SQL语句可在Postgres（即psql，pgAdmin）中工作，则它应在与R相连的客户端（如R）中工作。注意：crosstab需要扩展名。只需在SQL语句中用反斜杠转义双引号即可将其编译为R中的字符：

sql <- "SELECT * 
        FROM CROSSTAB(
           'SELECT factor1, factor2, 
                   ROUND(SUM(ST_AREA(geom))::numeric, 3) 
            FROM table 
            GROUP BY factor1, factor2 
            ORDER BY 1,2'
           ,
           'SELECT factor2 
            FROM table 
            GROUP BY factor2 
            ORDER BY factor2 '
         ) AS ct(\"factor1\" varchar, \"factor2value1\" varchar,
                 \"factor2value2\" varchar, \"factor2value3\" varchar)"

dbGetQuery(con, sql)

有什么方法可以在R中调用PostgreSQL tablefunc模块吗？

1 个答案: