如何查询mysql来计算数据库字段中的空值？

lyr7nygr 于 2021-06-21 发布在 Mysql

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如何查询mysql来计算数据库表列中的“null”值。我的查询总是0打印。

$rawm_jan_full=Yii::app()->db->createCommand("SELECT COUNT(trainings_id) AS trail_list from children WHERE MONTH(timestamp) = '1' AND YEAR(timestamp) ='".$previous_year."' AND trainings_id IS NULL ")->queryRow();

print_r($rawm_jan_full);

mysql php singlestore

来源：https://stackoverflow.com/questions/50171780/how-to-query-mysql-to-count-null-values-in-database-field

3条答案

按热度按时间

yqlxgs2m1#

$rawm_jan_full=Yii::app()->db->createCommand("SELECT COUNT(case when trainings_id is null then 1 else trainings_id end ) AS trail_list from children WHERE MONTH(timestamp) = '1' AND YEAR(timestamp) ='".$previous_year."' AND trainings_id IS NULL ")->queryRow();

 Replace COUNT(trainings_id )  with    COUNT(case when trainings_id is null then 1 else trainings_id end ) in order to include null in your count result

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busg9geu2#

请使用queryall而不是queryrow。

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bvuwiixz3#

你可以用queryall

$rawm_jan_full=Yii::app()->db->createCommand("SELECT COUNT(trainings_id) AS trail_list from children WHERE MONTH(timestamp) = '1' AND YEAR(timestamp) ='".$previous_year."' AND trainings_id IS NULL ")->Queryall();

print_r($rawm_jan_full);

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如何查询mysql来计算数据库字段中的空值？

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