在mysql中允许的列数是多少，类似地分组？

Question

我正在寻找我可以在＆＃34中使用多少列;按顺序＃34;例如，我有一个列名为asc，START_DATE asc，SKU_GROUP asc，并希望在order子句中添加SKU_NAME asc。我目前正在使用1组，但出于好奇，MySQL中可以使用多少个？

SELECT pop.SUB_ELEMENT, pop.NAME, sub_element.LDESC AS SUB_NAME, DATE_FORMAT(journey_visits.START_DATE, '%b %d %Y %h:%i %p' ) AS START_DATE, visit_sku.IS_CHECK,visit_sku.TYPE AS `SKU_TYPE`,brand.LDESC AS `SKU_GROUP`,sku.LDESC AS `SKU_NAME`,sku.SKU AS `MATERIAL` FROM visit_sku 
LEFT JOIN journey_visits  ON journey_visits.VISIT_ID = visit_sku.VISIT_ID 
LEFT JOIN pop ON journey_visits.POP_ID = pop.POPID
LEFT JOIN sub_element ON sub_element.SubElementID=pop.SUB_ELEMENT
LEFT JOIN sku ON visit_sku.SKU_ID = visit_sku.SKU_ID AND visit_sku.SKU_ID = sku.SKU  
LEFT JOIN brand ON sku.brandid = brand.BRANDID
WHERE  DATE(journey_visits.START_DATE)  BETWEEN '2016-04-01' AND '2016-04-03'
ORDER BY NAME, START_DATE, SKU_NAME

Answer 1

没有限制，您可以按结果集中的所有列排序或分组，但后者将无用。