计算联接表中的行，但如果不存在行则显示 0 - mysql

Posted 2023-03-28

【中文标题】计算联接表中的行，但如果不存在行则显示 0 - mysql

【英文标题】：count rows in joined table but display 0 if no rows exist - mysql

【发布时间】：2011-01-13 22:21:26

【问题描述】：

响应标题表是一个连接表，用于显示对特定调查的响应。如果没有行，因此没有响应，我希望计数显示为 0。但它正在跳过该行，因为在表中找不到连接参数 (survey_id)。

SELECT DATE_FORMAT(launched_date,'<nobr>%e-%b-%Y %H:%i:%s</nobr>'),
survey.NAME,
survey.iris_type,
survey.launched_by,
COUNT(response_header_2010.survey_id) AS response_count,
survey.survey_id,
survey.NAME 

FROM survey, response_header_2010

WHERE survey.STATUS='Live' 
AND survey.iris_type!='Recipient List'
AND response_header_2010.survey_id = survey.survey_id
AND client_id = '98'

GROUP BY  survey.survey_id, survey.NAME

ORDER BY response_count

【参考方案1】：

您想使用 LEFT JOIN 而不是您当前拥有的 INNER JOIN。

SELECT DATE_FORMAT(launched_date,'<nobr>%e-%b-%Y %H:%i:%s</nobr>'),
survey.NAME,
survey.iris_type,
survey.launched_by,
COUNT(response_header_2010.survey_id) AS response_count,
survey.survey_id,
survey.NAME 

FROM survey
LEFT JOIN response_header_2010
    ON survey.survey_id = response_header_2010.survey_id
WHERE survey.STATUS='Live' 
AND survey.iris_type!='Recipient List'
AND client_id = '98'

GROUP BY  survey.survey_id, survey.NAME

ORDER BY response_count