使用HAVING子句

时间：2015-06-28 14:33:05

标签： mysql unique-key

我为一个表创建了一个slug字段，它们需要是唯一的但是其中一些不是这样我认为我可以在它们的末尾添加随机字符以使它们唯一。

所以这是我的SELECT查询：

SELECT slug,count(*) as num FROM table GROUP BY slug HAVING num > 1

这是UPDATE查询：

UPDATE table SET slug = CONCAT(slug,'-',SUBSTRING(MD5(NOW()),1,2))

我无法将这2个查询合并。

2 个答案:

答案 0 :(得分：1)

您可以使用JOIN：

UPDATE mytable AS m
JOIN (SELECT slug
      FROM mytable 
      GROUP BY slug 
      HAVING COUNT(*) > 1) t
ON m.slug = t.slug      
SET m.slug = CONCAT(m.slug,'-',SUBSTRING(MD5(NOW()),1,2))

但是上面的问题是它没有生成唯一的字符串值。

Demo here

解决此问题的一种方法是使用由变量计算的行数：

UPDATE mytable AS m
CROSS JOIN (SELECT @row_number:=0, @slug := '') AS vars 
JOIN (
   SELECT slug
   FROM mytable 
   GROUP BY slug 
   HAVING COUNT(*) > 1 ) AS t ON m.slug = t.slug       
SET m.slug = CONCAT(m.slug, 
                    '-',
                    IF (@slug = m.slug,
                         IF (@slug := m.slug,@row_number:=@row_number+1, 
                                             @row_number:=@row_number+1),
                         IF (@slug := m.slug, @row_number:=1, 
                                              @row_number:=1)) 
                   )

Demo here

答案 1 :(得分：0)

尝试：

- !ruby/object:Google::APIClient::Schema::Youtube::V3::SearchResult
  data:
    kind: youtube#searchResult
    etag: ! '"Y3xTLFF3RLtHXX85JBgzzgp2Enw/RtuotxAng6F5sgkBlbg_LTSDi7s"'
    id:
      kind: youtube#video
      videoId: d5TsLsjtth8
    snippet:
      publishedAt: '2015-06-29T04:19:43.000Z'
      channelId: UCxdQj_S7w5O9lEm6v2uH_EA
      title: ! '◕‿◕☞ Funny Cats   Funny Cat Videos   Funny Cat Vine   Most Funny Cat
        2016  #2'
      description: funny vines clean version funny vines compilation 2015 new funny
        vines christian delgrosso funny vines cartoon voice overs funny fails dirt
        bike funny fails don't ...
      thumbnails:
        default:
          url: https://i.ytimg.com/vi/d5TsLsjtth8/default.jpg
        medium:
          url: https://i.ytimg.com/vi/d5TsLsjtth8/mqdefault.jpg
        high:
          url: https://i.ytimg.com/vi/d5TsLsjtth8/hqdefault.jpg
      channelTitle: ''
      liveBroadcastContent: none
- !ruby/object:Google::APIClient::Schema::Youtube::V3::SearchResult
  data:
    kind: youtube#searchResult
    etag: ! '"Y3xTLFF3RLtHXX85JBgzzgp2Enw/wXXxhJIuGlDPCjNyD6fxNnnp9yA"'
    id:
      kind: youtube#video
      videoId: 812W82_VDaA
    snippet:
      publishedAt: '2015-06-29T03:57:38.000Z'
      channelId: UCH9ev60cc7IFU_fqhBEpChw
      title: ! 'The Cat, the Vagabond and the Victim: A Cats in Trouble'
      description: ! 'The Cat, the Vagabond and the Victim: A Cats in Trouble http://www.amazon.co.uk/dp/B00U259982?tag=weiradlaemm06-21
        Feature * Heir of the cat... When ...'
      thumbnails:
        default:
          url: https://i.ytimg.com/vi/812W82_VDaA/default.jpg
        medium:
          url: https://i.ytimg.com/vi/812W82_VDaA/mqdefault.jpg
        high:
          url: https://i.ytimg.com/vi/812W82_VDaA/hqdefault.jpg
      channelTitle: ''
      liveBroadcastContent: none
- !ruby/object:Google::APIClient::Schema::Youtube::V3::SearchResult
  data:
    kind: youtube#searchResult
    etag: ! '"Y3xTLFF3RLtHXX85JBgzzgp2Enw/QWxRfjhIEHs95Rw1BSFjPwamYVY"'
    id:
      kind: youtube#video
      videoId: 4c2OvbRT1ZQ
    snippet:
      publishedAt: '2015-06-29T03:51:47.000Z'
      channelId: UCvrbFkZE2CXP8SVK3w5XS4A
      title: ネコのケンカ?  - cat fight? -
      description: 諦めなければいつかは叶うｗ.
      thumbnails:
        default:
          url: https://i.ytimg.com/vi/4c2OvbRT1ZQ/default.jpg
        medium:
          url: https://i.ytimg.com/vi/4c2OvbRT1ZQ/mqdefault.jpg
        high:
          url: https://i.ytimg.com/vi/4c2OvbRT1ZQ/hqdefault.jpg
      channelTitle: ''
      liveBroadcastContent: none
- !ruby/object:Google::APIClient::Schema::Youtube::V3::SearchResult
  data:
    kind: youtube#searchResult
    etag: ! '"Y3xTLFF3RLtHXX85JBgzzgp2Enw/Ezf1iUMSd4dY_5GJ7Rb0MxDaJcI"'
    id:
      kind: youtube#video
      videoId: -n040rD3nxI
    snippet:
      publishedAt: '2015-06-29T02:40:30.000Z'
      channelId: UCsukgxUI8Gkju1lKCOKBlcQ
      title: Funny Cat Joke
      description: King of shitty 10 second videos.
      thumbnails:
        default:
          url: https://i.ytimg.com/vi/-n040rD3nxI/default.jpg
        medium:
          url: https://i.ytimg.com/vi/-n040rD3nxI/mqdefault.jpg
        high:
          url: https://i.ytimg.com/vi/-n040rD3nxI/hqdefault.jpg
      channelTitle: realchris1Returns
      liveBroadcastContent: none
- !ruby/object:Google::APIClient::Schema::Youtube::V3::SearchResult
  data:
    kind: youtube#searchResult
    etag: ! '"Y3xTLFF3RLtHXX85JBgzzgp2Enw/TNpAkcwloC58Xi8aCVsmSXMspyA"'
    id:
      kind: youtube#video
      videoId: e5LJvFUM9k4
    snippet:
      publishedAt: '2015-06-29T02:40:12.000Z'
      channelId: UC64ta8zKaK5gXWPgTk37VNA
      title: ! 'Sam & Cat Season 1 : FULL Episode 1 - 36 FREE STREAMING HD QUALITY'
      description: ! 'Sam & Cat - Season 1 : Episode 1 - 36 FULL STREAMING , Visit
        Link On List All Episode http://youtube.vg/HVDX3KE8 And Enjoyed For 720p Until
        1280p High ...'
      thumbnails:
        default:
          url: https://i.ytimg.com/vi/e5LJvFUM9k4/default.jpg
        medium:
          url: https://i.ytimg.com/vi/e5LJvFUM9k4/mqdefault.jpg
        high:
          url: https://i.ytimg.com/vi/e5LJvFUM9k4/hqdefault.jpg
      channelTitle: ''
      liveBroadcastContent: none
- !ruby/object:Google::APIClient::Schema::Youtube::V3::SearchResult
  data:
    kind: youtube#searchResult
    etag: ! '"Y3xTLFF3RLtHXX85JBgzzgp2Enw/HcqCoYiw3qvNoxloToHL_LeyAk4"'
    id:
      kind: youtube#video
      videoId: x4RB5oF72AU
    snippet:
      publishedAt: '2015-06-29T02:07:49.000Z'
      channelId: UCFPV7m24Y-KM66v_aScWTRQ
      title: Kucing Berani serang Ular ( cat vs snake )
      description: Kucing Berani serang Ular ( cat vs snake )
      thumbnails:
        default:
          url: https://i.ytimg.com/vi/x4RB5oF72AU/default.jpg
        medium:
          url: https://i.ytimg.com/vi/x4RB5oF72AU/mqdefault.jpg
        high:
          url: https://i.ytimg.com/vi/x4RB5oF72AU/hqdefault.jpg
      channelTitle: ''
      liveBroadcastContent: none
- !ruby/object:Google::APIClient::Schema::Youtube::V3::SearchResult
  data:
    kind: youtube#searchResult
    etag: ! '"Y3xTLFF3RLtHXX85JBgzzgp2Enw/dTOXDCV4PSk4woUH3RTDfYWH7sc"'
    id:
      kind: youtube#video
      videoId: cfuq0Qs4154
    snippet:
      publishedAt: '2015-06-29T02:05:19.000Z'
      channelId: UCH1vIUNu9z4hosPO4IiEDKg
      title: MY CUTE CAT VIDEO XD
      description: I MADE THIS VIDEO FOR FUN BECAUSE IT WOULD BE A CUTE FUN IDEAXD.
      thumbnails:
        default:
          url: https://i.ytimg.com/vi/cfuq0Qs4154/default.jpg
        medium:
          url: https://i.ytimg.com/vi/cfuq0Qs4154/mqdefault.jpg
        high:
          url: https://i.ytimg.com/vi/cfuq0Qs4154/hqdefault.jpg
      channelTitle: Nlg31
      liveBroadcastContent: none
- !ruby/object:Google::APIClient::Schema::Youtube::V3::SearchResult
  data:
    kind: youtube#searchResult
    etag: ! '"Y3xTLFF3RLtHXX85JBgzzgp2Enw/3VF2zQBJ71Si2Zcar34cJGKDp6A"'
    id:
      kind: youtube#playlist
      playlistId: PLMPGTLYCAiq9gAh6UnpaXx_PtKENmh1P6
    snippet:
      publishedAt: '2015-06-29T01:52:34.000Z'
      channelId: UCl65ZDJ_D2QnvzknOzC_Syw
      title: Black Cat
      description: ''
      thumbnails:
        default:
          url: https://i.ytimg.com/vi/UexNlx4mj1g/default.jpg
        medium:
          url: https://i.ytimg.com/vi/UexNlx4mj1g/mqdefault.jpg
        high:
          url: https://i.ytimg.com/vi/UexNlx4mj1g/hqdefault.jpg
      channelTitle: ''
      liveBroadcastContent: none
- !ruby/object:Google::APIClient::Schema::Youtube::V3::SearchResult
  data:
    kind: youtube#searchResult
    etag: ! '"Y3xTLFF3RLtHXX85JBgzzgp2Enw/nldPN_K-A-jNCqF0I3MlOjByOog"'
    id:
      kind: youtube#video
      videoId: INraypSN3Q0
    snippet:
      publishedAt: '2015-06-29T01:35:33.000Z'
      channelId: UCVbqIMbp2qRhK6-YXYkOF7g
      title: ! 'Aksi kucing dubsmash lucu.. #funny #cat #pet'
      description: Hilarious cats.
      thumbnails:
        default:
          url: https://i.ytimg.com/vi/INraypSN3Q0/default.jpg
        medium:
          url: https://i.ytimg.com/vi/INraypSN3Q0/mqdefault.jpg
        high:
          url: https://i.ytimg.com/vi/INraypSN3Q0/hqdefault.jpg
      channelTitle: ''
      liveBroadcastContent: none
- !ruby/object:Google::APIClient::Schema::Youtube::V3::SearchResult
  data:
    kind: youtube#searchResult
    etag: ! '"Y3xTLFF3RLtHXX85JBgzzgp2Enw/2_PMO7FctA_79aqVhV0D83Yw7VY"'
    id:
      kind: youtube#video
      videoId: Bt6NgC0peLI
    snippet:
      publishedAt: '2015-06-29T01:06:00.000Z'
      channelId: UCpM_hmOVus872lSLIdbirXQ
      title: ! 'Conversation With a Cat: Should I Go Vegan?'
      description: I'm 80% vegan, but my cat won't hesitate to eat lizards/birds...
      thumbnails:
        default:
          url: https://i.ytimg.com/vi/Bt6NgC0peLI/default.jpg
        medium:
          url: https://i.ytimg.com/vi/Bt6NgC0peLI/mqdefault.jpg
        high:
          url: https://i.ytimg.com/vi/Bt6NgC0peLI/hqdefault.jpg
      channelTitle: LifeLibertyNow
      liveBroadcastContent: none

演示：http://sqlfiddle.com/#!9/01c68/1

我使用的是UPDATE t , ( SELECT slug FROM t GROUP BY slug HAVING count(*) > 1 ) x SET t.slug = CONCAT(t.slug,'-',SUBSTRING(MD5(rand()),1,2)) WHERE t.slug = x.slug ; 而不是rand()，因为后者不会提供唯一的字符串。

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