ranking

MySQL Group By with top N number of each kind

断了今生、忘了曾经 提交于 2019-11-26 14:39:42
问题 I have a table like this: Rank Letter 1 A 2 A 3 B 4 A 5 C 6 A 7 C 8 C 9 B 10 C And I need the top 2 of each letter ordered by ascending rank: Rank Letter 1 A 2 A 3 B 5 C 7 C 9 B How would I do it? It's fairly straightforward to get just the top 1 using GROUP BY, but I can't seem to get it working for multiple entries 回答1: select distinct rank, letter from table1 t2 where rank in (select top 2 rank from table1 t2 where t2.letter = t1.letter order by rank) order by letter, rank EDIT: (my first

selecting top N rows for each group in a table

会有一股神秘感。 提交于 2019-11-26 12:42:12
问题 I am facing a very common issue regarding \"Selecting top N rows for each group in a table\". Consider a table with id, name, hair_colour, score columns. I want a resultset such that, for each hair colour, get me top 3 scorer names. To solve this i got exactly what i need on Rick Osborne\'s blogpost \"sql-getting-top-n-rows-for-a-grouped-query\" That solution doesn\'t work as expected when my scores are equal. In above example the result as follow. id name hair score ranknum -----------------

78 Ranking SVM

大憨熊 提交于 2019-11-26 10:17:13
0 引言 通过训练SVM获取特征向量权重参数,进而对特征进行排序的方法,成为Ranking SVM. 1 中文版介绍 https://blog.csdn.net/clheang/article/details/45767103 2 H. Joachims 提供的Ranking SVM的源码实现 http://www.cs.cornell.edu/people/tj/svm_light/svm_rank.html 3 Ranking SVM 在dlib中的实现 http://dlib.net/ 来源: https://www.cnblogs.com/ghjnwk/p/11317711.html

h5排名展示

久未见 提交于 2019-11-26 08:23:09
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String similarity algorithms?

旧时模样 提交于 2019-11-26 07:24:06
问题 I need to compare 2 strings and calculate their similarity, to filter down a list of the most similar strings. Eg. searching for \"dog\" would return dog doggone bog fog foggy Eg. searching for \"crack\" would return crack wisecrack rack jack quack I have come across: QuickSilver LiquidMetal Do you know of any more string similarity algorithms? 回答1: It seems you are needing some kind of fuzzy matching. Here is java implementation of some set of similarity metrics http://www.dcs.shef.ac.uk/

A better similarity ranking algorithm for variable length strings

邮差的信 提交于 2019-11-26 03:24:15
问题 I\'m looking for a string similarity algorithm that yields better results on variable length strings than the ones that are usually suggested (levenshtein distance, soundex, etc). For example, Given string A: \"Robert\", Then string B: \"Amy Robertson\" would be a better match than String C: \"Richard\" Also, preferably, this algorithm should be language agnostic (also works in languages other than English). 回答1: Simon White of Catalysoft wrote an article about a very clever algorithm that

A better similarity ranking algorithm for variable length strings

泪湿孤枕 提交于 2019-11-25 23:12:26
I'm looking for a string similarity algorithm that yields better results on variable length strings than the ones that are usually suggested (levenshtein distance, soundex, etc). For example, Given string A: "Robert", Then string B: "Amy Robertson" would be a better match than String C: "Richard" Also, preferably, this algorithm should be language agnostic (also works in languages other than English). Simon White of Catalysoft wrote an article about a very clever algorithm that compares adjacent character pairs that works really well for my purposes: http://www.catalysoft.com/articles

Using LIMIT within GROUP BY to get N results per group?

吃可爱长大的小学妹 提交于 2019-11-25 21:35:19
问题 The following query: SELECT year, id, rate FROM h WHERE year BETWEEN 2000 AND 2009 AND id IN (SELECT rid FROM table2) GROUP BY id, year ORDER BY id, rate DESC yields: year id rate 2006 p01 8 2003 p01 7.4 2008 p01 6.8 2001 p01 5.9 2007 p01 5.3 2009 p01 4.4 2002 p01 3.9 2004 p01 3.5 2005 p01 2.1 2000 p01 0.8 2001 p02 12.5 2004 p02 12.4 2002 p02 12.2 2003 p02 10.3 2000 p02 8.7 2006 p02 4.6 2007 p02 3.3 What I\'d like is only the top 5 results for each id: 2006 p01 8 2003 p01 7.4 2008 p01 6.8