Question

基本上我有以下存储过程：

BEGIN
SET @query := CONCAT("SELECT *,
sqrt( 
        (POW(a.Latitude - co.CenterLatitude, 2)* 68.1 * 68.1) + 
        (POW(a.Longitude - co.CenterLongitude, 2) * 53.1 * 53.1) 
 ) AS distance
FROM table1 as r
JOIN table2 as co ON co.field1 = r.field2
JOIN table3 AS a ON r.field1 = a.field2
WHERE ",rid);

PREPARE stmt FROM @query;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

END

它有以下传递：

IN rid varchar(500), lat double, lon double

但我需要传递纬度和经度变量。我已经尝试设置它们然后将它们添加到查询中但它没有识别它们。这就是我想做的不成功的事情：

    BEGIN
    SET @lat := lat;
    SET @lon := lon;
    SET @query := CONCAT("SELECT *,
    sqrt( 
            (POW(a.Latitude - @lat, 2)* 68.1 * 68.1) + 
            (POW(a.Longitude - @lon, 2) * 53.1 * 53.1) 
     ) AS distance
    FROM table1 as r
    JOIN table2 as co ON co.field1 = r.field2
    JOIN table3 AS a ON r.field1 = a.field2
    WHERE ",rid);

    PREPARE stmt FROM @query;
    EXECUTE stmt;
    DEALLOCATE PREPARE stmt;

    END

我不知道如何做到这一点。有没有人有什么建议？提前谢谢!!

Answer 1

您可以将?占位符放在预准备语句中，然后在执行时提供值。

SET @query := CONCAT("SELECT *,
sqrt( 
        (POW(a.Latitude - ?, 2)* 68.1 * 68.1) + 
        (POW(a.Longitude - ?, 2) * 53.1 * 53.1) 
 ) AS distance
FROM table1 as r
JOIN table2 as co ON co.field1 = r.field2
JOIN table3 AS a ON r.field1 = a.field2
WHERE ",rid);
PREPARE stmt FROM @query;
EXECUTE stmt USING @lat, @lon;

Answer 2

Barmar的答案将是我首选的解决方案，但举一个例子来说明我最初的评论建议......

BEGIN
SET @query := CONCAT("SELECT *,
sqrt( 
        (POW(a.Latitude - ", lat, ", 2)* 68.1 * 68.1) + 
        (POW(a.Longitude - ", lon, ", 2) * 53.1 * 53.1) 
 ) AS distance
FROM table1 as r
JOIN table2 as co ON co.field1 = r.field2
JOIN table3 AS a ON r.field1 = a.field2
WHERE ",rid);

PREPARE stmt FROM @query;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

END

MySql存储过程，如何使用CONCAT

2 个答案: