mysql - sql查询通过逗号分隔获取结果

Question

我有 2 个表，想通过逗号分隔获取所有类别。

SELECT object_id, meta_value, name, event_level, event_temp_id FROM 
wp_em_meta, wp_terms, wp_em_events WHERE wp_em_meta.meta_key = 'category-image' 
AND wp_em_meta.object_id IN ($eventtid) AND wp_em_meta.object_id = wp_terms.term_id 
AND wp_em_meta.object_id = wp_em_events.event_temp_id

例如：

表格1

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在附加的图像中，我想获取结果为

Answer 1

你可以在 MySQL 中使用GROUP_CONCAT()函数

SELECT object_id, 
GROUP_CONCAT(event_level) as meta_value, 
name, event_level, event_temp_id FROM 
wp_em_meta, wp_terms, wp_em_events 
WHERE wp_em_meta.meta_key = 'category-image' 
AND wp_em_meta.object_id IN ($eventtid) AND wp_em_meta.object_id = wp_terms.term_id 
AND wp_em_meta.object_id = wp_em_events.event_temp_id
GROUP BY object_id