比较mysql中的两个逗号分隔值并获取匹配的计数

Compare comma separated values in mysql and get the matched output in countcolumn

比较mysql中的逗号分隔值,并在countcolumn中获取匹配的输出

Example:

id   values 
 1    1,2,3
 2    3
 3    1,3

By comparing id 1 and 2 the output should be 1

通过比较id 1和2,输出应为1

By comparing id 2 and 3 the output should be 1

通过比较id 2和3,输出应为1

By comparing id 3 and 1 the output should be 2

通过比较id 3和1,输出应为2

2 个解决方案

#1

Firstly, the data you listed should really be stored in a format where each row of the database stores a single id and a single value, i.e. the 3-element list would correspond to 3 rows. If that change was made to your structure then the following answer would be relevant Compare similarities between two result sets

首先,您列出的数据实际上应该以数据库的每一行存储单个ID和单个值的格式存储,即3元素列表对应于3行。如果对您的结构进行了更改,那么以下答案将是相关的。比较两个结果集之间的相似性

As it stands though, here's a nice little MySQL function I put together that you could use for your purposes. This takes in 2 arguments which are comma-separated lists and will return the number of elements in list 1 that appear in list 2.

尽管如此,这里有一个很好的小MySQL功能,我可以将它用于你的目的。这将引入2个以逗号分隔的列表参数,并返回列表1中出现在列表2中的元素数。

This will not as it stands prevent duplicate IDs in list 1 being counted twice in list 2 (i.e. '1,1,2' and '1,2' would return a value of 3) but you could figure out how to adjust this fairly easily to do that if you so wished.

这并不是因为它可以防止列表1中的重复ID在列表2中被计数两次(即'1,1,2'和'1,2'将返回值3)但是你可以弄清楚如何公平地调整它如果你愿意,很容易做到这一点。

To use this, just do

要使用它,就这样做

SELECT 
    countMatchingElements( '3' , '1,3' ) AS testCase1
    countMatchingElements( '1,2,3' , '1,3' ) AS testCase2
    countMatchingElements( '3' , '1,2,3' ) AS testCase3;

The stored function logic is as follows

存储的功能逻辑如下

CREATE DEFINER = `yourUserGoesHere`@`%` FUNCTION `countMatchingElements`(inFirstList VARCHAR(1000), inSecondList VARCHAR(1000))
 RETURNS tinyint(3) unsigned
    NO SQL
    DETERMINISTIC
    SQL SECURITY INVOKER
BEGIN
    DECLARE numReturn TINYINT UNSIGNED DEFAULT 0;
    DECLARE idsInFirstList TINYINT UNSIGNED;
    DECLARE currentListItem VARCHAR(255) DEFAULT '';
    DECLARE currentID TINYINT UNSIGNED;

    SET idsInFirstList = ( CHAR_LENGTH( inFirstList ) + 1 ) - CHAR_LENGTH( REPLACE( inFirstList , ',' , '' ) );
    SET currentID = 1;

    -- Loop over inFirstList, and for each element that is in inSecondList increment numReturn
    firstListLoop: REPEAT

        SET currentListItem = SUBSTRING_INDEX( SUBSTRING_INDEX( inFirstList , ',' , currentID ) , ',' , -1 );

        IF FIND_IN_SET( currentListItem , inSecondList ) THEN

            SET numReturn = numReturn + 1;

        END IF;

        SET currentID = currentID + 1;

    UNTIL currentID > idsInFirstList
    END REPEAT firstListLoop;

    RETURN numReturn;
END

2 个解决方案

#1

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