Mysql 按类型限制查询结果

我有一张有两种不同类型（图像和视频）的桌子。我想得到每种类型最多2行。。。有什么帮助吗？因此，结果集将是4行

这是我目前的查询（这只是从1 type；image中获取的行）：

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进行两个单独的查询并使用两个结果集的并集

SELECT DISTINCT mm.mm_id, mm.mm_title, mm.mm_hash FROM boomla_multimedia mm, 
  boomla_multimedia_domain md 
WHERE mm.mm_id = md.mm_id AND cat_id = 4 AND md.dom_id = 26 AND mm.mm_published = 1
  AND mm.mm_media_type = 'image' ORDER BY mm.mm_id DESC LIMIT 0, 2

UNION

-- add here the select for 'video' type

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进行两个单独的查询并使用两个结果集的并集

SELECT DISTINCT mm.mm_id, mm.mm_title, mm.mm_hash FROM boomla_multimedia mm, 
  boomla_multimedia_domain md 
WHERE mm.mm_id = md.mm_id AND cat_id = 4 AND md.dom_id = 26 AND mm.mm_published = 1
  AND mm.mm_media_type = 'image' ORDER BY mm.mm_id DESC LIMIT 0, 2

UNION

-- add here the select for 'video' type

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请使用格式化选项（

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）使其下次更具可读性；）请使用格式化选项（

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）使其下次更具可读性；）