Postgres選擇多個選擇爲

我想在PostGIS函數中使用兩個SELECT語句的輸出。Postgres選擇多個選擇爲

這樣做的正確語法是什麼？我在第二個SELECT語句處或附近收到語法錯誤。

SELECT ST_Split(tracks, roads) 
FROM 
(
    SELECT * FROM (SELECT ST_Buffer(road_geom,50) FROM table1 WHERE a = '' AND b = '') as roads, 
    SELECT * FROM (SELECT the_geom FROM table2 WHERE c = '' AND d = '') as tracks 

)

錯誤輸出：

ERROR: syntax error at or near "SELECT" 
LINE 5: SELECT * FROM (SELECT the_geom FROM table2... 
    ^
********** Error ********** 
ERROR: syntax error at or near "SELECT" 
SQL state: 42601 
Character: 178

謝謝！

來源

2013-10-25 Matt

演示使用CTE的一種方法：在http://www.postgresql.org/docs/current/static/queries-with.html

來源

2013-10-25 16:54:18 bma

感謝您的快速和準確的回覆

WITH roads as (SELECT ST_Buffer(road_geom,50) as road FROM table1 WHERE a = '' AND b = ''), tracks as (SELECT the_geom as track FROM table2 WHERE c = '' AND d = '') SELECT ST_Split((select track from tracks), (select road from roads));

文檔。 – Matt

有一點需要注意的是，從「道路」和「軌道」虛擬表（「WITH」塊中的子句）選擇'' - 如果它們能返回多於一行的查詢將會失敗，所以你應該給它們兩個添加「LIMIT 1」（我的意思是在「WITH」子句中）。 – bma

是的 - 我最終將循環中的分割包裝起來。再次感謝你的幫助！ – Matt

Postgres選擇多個選擇爲

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