How to convert one row into multiple rows in mysql

Mysql method to turn one line into multiple lines: 1. To turn one line into multiple lines, the code is [substring_index(substring_index( a.rn,',',b.help_topic_id 1 ),',', - 1)]; 2. Convert multiple columns into multiple rows.

Mysql method to turn one row into multiple rows:

Put

Convert to

SELECT substring_index(substring_index( a.rn,',',b.help_topic_id + 1 ),',' ,- 1) AS rn FROM (select '1,2,3,4' as rn) a JOIN mysql.help_topic b ON b.help_topic_id < (length(a.rn) - length( replace(a.rn, ',', '') ) + 1)

Convert Picture A to Picture B

Picture a

图b

SELECT substring_index(substring_index( a.rn,',',b.help_topic_id + 1 ), ',' ,- 1 ) AS rn FROM (select SUBSTR(GROUP_CONCAT( REPEAT(CONCAT(number,','),fre) SEPARATOR ''),1,LENGTH(GROUP_CONCAT( REPEAT(CONCAT(number,','),fre) SEPARATOR ''))-1) as rn from numbers ) a JOIN mysql.help_topic b ON b.help_topic_id < (length(a.rn) - length( replace(a.rn, ',', '') ) + 1)

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