Question

我们有MYTABLE的查询，并希望加入OTHER_TABLE以从中获取链接数据。但它似乎没有用。

SELECT *,3956 * 2 * ASIN(SQRT( POWER(SIN(($orig_lat - abs(wlatitude)) * pi()/180 / 2),2) 
+ COS($orig_lat * pi()/180 ) * COS(abs(wlatitude) *  pi()/180) * POWER(SIN(($orig_lon - wlongitude) *  pi()/180 / 2), 2) )) 
as distance FROM MYTABLE dest having distance < $dist ORDER BY distance

如何在不出错的情况下将此添加到查询中？

LEFT JOIN OTHER_TABLE ON MYTABLE.column=OTHER_TABLE.column

Answer 1

无论你做什么，你都不会得到'错误'，而是你不需要的结果。

如果连接是1到1，或多对一，则不会得到任何相乘的行。

如果连接是一对多，则右侧的每个对应行数可能会在左侧获得乘法内容，具体取决于您的条件。

请参阅http://en.wikipedia.org/wiki/Relational_algebra#Joins_and_join-like_operators了解连接逻辑。

到您的查询，对于任何其他查询，techincal订单是：

select # ... 
from # table 
join # table
on  # condition
join # another table
on # another condition
where # condition
group # clause
having # condition applied after grouping
order by # ..

Answer 2

没有深入查询，但它应该是这样的。

SELECT
    *,
    3956 * 2 * ASIN(SQRT( POWER(SIN(($orig_lat - abs(wlatitude)) * pi()/180 / 2),2) + COS($orig_lat * pi()/180 ) * COS(abs(wlatitude) *  pi()/180) * POWER(SIN(($orig_lon - wlongitude) *  pi()/180 / 2), 2) ))
        as distance
FROM MYTABLE dest
LEFT JOIN OTHER_TABLE ON MYTABLE.column=OTHER_TABLE.column
HAVING distance < $dist
ORDER BY distance

Answer 3

SELECT *, 3956 * 2 * ASIN(SQRT( POWER(SIN(($orig_lat - abs(wlatitude)) * pi()/180 / 2),2) 
+ COS($orig_lat * pi()/180 ) * COS(abs(wlatitude) *  pi()/180) * POWER(SIN(($orig_lon - wlongitude) *  pi()/180 / 2), 2) )) AS distance 
FROM MYTABLE dest 
LEFT JOIN OTHER_TABLE ON dest.column = OTHER_TABLE.column 
HAVING distance < $dist ORDER BY distance

Answer 4

使用左连接可能有可能获得重复尝试使用distinct也使用适当的表别名

SELECT DISTINCT 
  *,
  3956 * 2 * ASIN(
    SQRT(
      POWER(
        SIN(
          ($orig_lat - ABS(dest.wlatitude)) * PI() / 180 / 2
        ),
        2
      ) + COS($orig_lat * PI() / 180) * COS(ABS(dest.wlatitude) * PI() / 180) * POWER(
        SIN(($orig_lon - dest.wlongitude) * PI() / 180 / 2),
        2
      )
    )
  ) AS distance 
FROM
  MYTABLE dest 
  LEFT JOIN OTHER_TABLE o ON dest.column=o.column
HAVING distance < $dist 
ORDER BY distance

MYSQL将JOIN添加到查询中

4 个答案: