我试图获得一个带有动态列的数据透视表。当user_id是一个字符串时,它可以正常工作,但是如果它是一个int,那么它似乎会失败
到目前为止,在过去的问题帮助下,我得到的是:
CREATE TABLE measure2 (inspection_date
date, user_id
int, score
int, comment text) ;
INSERT INTO measure2 (inspection_date
, user_id
, score
, comment) VALUES ('2012-10-16', 0, 0, null), ('2012-10-16', 1, 0, null), ('2012-10-16', 2, 0, null), ('2012-10-16', 3, 0, null), ('2012-10-17', 0, 1, null), ('2012-10-17', 1, 1, null), ('2012-10-17', 2, 1, null), ('2012-10-18', 3, 1, null) ;
SET @sql = NULL; SELECT GROUP_CONCAT(DISTINCT CONCAT( 'max(case when user_id = ''', user_id, ''' then score end) AS ', user_id ) ) INTO @sql FROM measure2;
SET @sql = CONCAT('SELECT inspection_date, ', @sql, ' FROM measure2 GROUP BY inspection_date');
PREPARE stmt FROM @sql; EXECUTE stmt; DEALLOCATE PREPARE stmt; 参见:http : //sqlfiddle.com/#!2/eab24/1
我确定这很简单,但是我想念什么呢?
谢谢
由于值在int其中,因此您要将它们设为列名,因此必须将值包装在反引号中
该SQL将看起来像:
max(case when user_id = 1 then score end) as 1
完整的查询将是:
SET @sql = NULL; SELECT GROUP_CONCAT(DISTINCT CONCAT( 'max(case when user_id = ''', user_id, ''' then score end) AS ', user_id, '
' ) ) INTO @sql FROM measure2;
SET @sql = CONCAT('SELECT inspection_date, ', @sql, ' FROM measure2 GROUP BY inspection_date');
PREPARE stmt FROM @sql; EXECUTE stmt; DEALLOCATE PREPARE stmt;来源:stack overflow
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