Sql 从多个表中获取数据_Sql_Postgresql_Select_Postgis

Sql 从多个表中获取数据

sql postgresql select

Sql 从多个表中获取数据,sql,postgresql,select,postgis,Sql,Postgresql,Select,Postgis,我有三张桌子——商店、土豆和西红柿（西红柿桌子看起来像土豆桌子）。马铃薯表中的id准确地说是商店的id——因此该商店的马铃薯价格 +----+-------+-----------+ | potato | +----+-------+-----------+ | id | price | date_time | +----+-------+-----------+ +----+-----+-----+------+------+ |

我有三张桌子——商店、土豆和西红柿（西红柿桌子看起来像土豆桌子）。马铃薯表中的id准确地说是商店的id——因此该商店的马铃薯价格

+----+-------+-----------+
|         potato         |
+----+-------+-----------+
| id | price | date_time |
+----+-------+-----------+

+----+-----+-----+------+------+  
|             shop             |
+----+-----+-----+------+------+
| id | lat | lng | name | geom |
+----+-----+-----+------+------+

我想做的是，选择离某个位置最多10公里的所有商店，以及西红柿和土豆的价格

现在，我有了这个查询，可以选择商店，还有土豆价格

SELECT
    shop.lat,
    shop.lng,
    shop.id,
    potato.date_time AS potato_date,
    potato.price as potato_price 
FROM 
    shop,
    potato 
WHERE
    potato.id = shop.id AND 
    ST_DWithin(
        ST_GeomFromText('POINT(xx.xxxxxx yy.yyyyyy)',4326),
        shop.geom,
        10*1000,
        true
    );

但我还想知道那家商店西红柿的价格。怎么做呢？

使用左连接

SELECT 
   shop.lat
  , shop.lng
  , shop.id
  , potato.date_time AS potato_date
  , potato.price as potato_price 
  , tomato.date_time as tomato_date
  , tomato.price as tomato_price
FROM shop
LEFT JOIN potato on potato.ID = shop.ID
LEFT JOIN tomato  on tomato.ID =  shop.ID 
WHERE  ST_DWithin(ST_GeomFromText('POINT(xx.xxxxxx yy.yyyyyy)',4326), shop.geom,10*1000, true );

如果每家商店都卖西红柿和土豆，你可以使用“内部联接”