Question

有人知道为什么CASE WHEN（）总是返回“是”，即使有一些数据记录（按RecordID）在data_records_ga表中没有条目吗？

目前我不确定为什么最外面的SELECT * FROM (...) AS X在那里，但是我的问题在于内部SELECT data_records.RecordID, (...及其相关的子查询。

对于不满足子查询条件的记录，我希望看到“否”，并将其插入“已完成”字段。

    SELECT * FROM (
        SELECT
            data_records.RecordID,
            (
                CASE WHEN (
                    SELECT COUNT(drga.Comment) AS count
                    FROM `data_records_ga` drga
                    INNER JOIN `data_records` dr
                    ON dr.RecordID = drga.RecordID
                    WHERE drga.FieldName = 'GA_completed'
                    AND drga.Comment = 1
                    AND dr.RecordID = drga.RecordID
                    HAVING COUNT(drga.Comment) > 0
                ) > 0
                THEN 'Yes'
                ELSE 'No'
                END
            ) AS Completed,
        FROM `data_records`
        LEFT JOIN data_records_ga on data_records.RecordID = data_records_ga.RecordID
        GROUP BY RecordID ORDER BY RecordID
    ) AS X

Answer 1

这很可能是因为您的子查询未以任何方式链接到其父查询，因此您只选择了将获得“是”的行。尝试将此行添加到子查询的WHERE子句中：

AND dr.RecordID = data_records.RecordID

并删除：

AND dr.RecordID = drga.RecordID

上一行是多余的，因为您已经在子查询中将表连接在一起了。

MySQL从子查询的另一个表中获取列数

1 个答案: