mysql - 即使字段为空，如何运行 SQL 查询来返回

Question

目前，我正在运行此 SQL 查询来检索商店定位器的自定义帖子。一切都很好，除了我希望它返回项目，即使“电话”字段为空。截至目前，它只会拉入已填写该字段的内容。

这是我的查询运行时的样子:

有人知道吗？ (还有更有效的方法来运行它吗？)

SELECT   wp_posts.post_title as name, 

        address.meta_value as address,
        latitude.meta_value as lat,
        longitude.meta_value as lng,
        telephone.meta_value as phone,


        ( 3959 * acos(
        cos( radians( '%s' ) ) *
        cos( radians( CONVERT( latitude.meta_value, DECIMAL( 10, 6 ) ) ) ) *
        cos( radians( CONVERT( longitude.meta_value, DECIMAL( 10, 6 ) ) ) - radians( '%s' ) ) +
        sin( radians( '%s' ) ) * sin( radians( CONVERT( latitude.meta_value, DECIMAL( 10, 6 ) ) ) )
         ) ) AS distance

        FROM wp_postmeta as address, wp_postmeta as latitude, wp_postmeta as longitude, wp_postmeta as telephone,
         wp_posts

WHERE   
    (wp_posts.ID = address.post_id
        AND address.meta_key = '_dealer_address' )  

AND     (wp_posts.ID = latitude.post_id
        AND latitude.meta_key = '_dealer_latitude' )

AND     (wp_posts.ID = longitude.post_id
        AND longitude.meta_key = '_dealer_longitude' )      

AND     (wp_posts.ID = telephone.post_id
        AND telephone.meta_key = '_dealer_telephone' )  

Answer 1

根据 Marc B 在评论中的建议发布答案。

     SELECT  wp_posts.post_title as name, 
address.meta_value as address,
 latitude.meta_value as lat,
 longitude.meta_value as lng,
 telephone.meta_value as telephone,

   ( 3959 * acos(
    cos( radians( '%s' ) ) *
    cos( radians( CONVERT( latitude.meta_value, DECIMAL( 10, 6 ) ) ) ) *
    cos( radians( CONVERT( longitude.meta_value, DECIMAL( 10, 6 ) ) ) - radians( '%s' ) ) +
    sin( radians( '%s' ) ) * sin( radians( CONVERT( latitude.meta_value, DECIMAL( 10, 6 ) ) ) )
     ) ) AS distance

FROM wp_posts
LEFT JOIN wp_postmeta AS address ON(
wp_posts.ID = address.post_id
AND address.meta_key = '_dealer_address'
)
LEFT JOIN wp_postmeta AS latitude ON(
wp_posts.ID = latitude.post_id
AND latitude.meta_key = '_dealer_latitude'
)
LEFT JOIN wp_postmeta AS longitude ON(
wp_posts.ID = longitude.post_id
AND longitude.meta_key = '_dealer_longitude'
)
LEFT JOIN wp_postmeta AS telephone ON(
wp_posts.ID = telephone.post_id
AND telephone.meta_key = '_dealer_telephone'
)
WHERE wp_posts.post_type = 'dealers' HAVING distance < '%s' ORDER BY distance LIMIT 0 ,         20