SELECT 语句中的 MySQL 存储过程变量

Question

我正在尝试创建一个存储过程。这是我到目前为止(不工作):

DELIMITER |
CREATE PROCEDURE getNearestCities(IN cityID INT)
    BEGIN
        DECLARE cityLat FLOAT;
        DECLARE cityLng FLOAT;
        SET cityLat = SELECT cities.lat FROM cities WHERE cities.id = cityID;
        SET cityLng = SELECT cities.lng FROM cities WHERE cities.id = cityID;
        SELECT *, HAVERSINE(cityLat,cityLng, cities.lat, cities.lng) AS dist FROM cities ORDER BY dist LIMIT 10;
    END |

HAVERSINE 是我创建的一个运行良好的函数。如您所见，我正在尝试从 cities 表中获取城市的 ID，然后将 cityLat 和 cityLng 设置为该记录的其他一些值。我显然在这里使用 SELECT 做错了。

这有可能吗？似乎应该如此。任何帮助都将不胜感激。

Answer 1

更正了一些内容并添加了替代选择 - 根据需要删除。

DELIMITER |

CREATE PROCEDURE getNearestCities
(
IN p_cityID INT -- should this be int unsigned ?
)
BEGIN

DECLARE cityLat FLOAT; -- should these be decimals ?
DECLARE cityLng FLOAT;

    -- method 1
    SELECT lat,lng into cityLat, cityLng FROM cities WHERE cities.cityID = p_cityID;

    SELECT 
     b.*, 
     HAVERSINE(cityLat,cityLng, b.lat, b.lng) AS dist 
    FROM 
     cities b 
    ORDER BY 
     dist 
    LIMIT 10;

    -- method 2
    SELECT   
      b.*, 
      HAVERSINE(a.lat, a.lng, b.lat, b.lng) AS dist
    FROM     
      cities AS a
    JOIN cities AS b on a.cityID = p_cityID
    ORDER BY 
      dist
    LIMIT 10;

END |

delimiter ;