尝试填充别名列，其中X = 1，多个连接，子查询

Question

我在下面的查询中返回了我期望的所有列。但是，date_met列似乎返回一个。）所有结果的相同日期和b。）任何结果的错误日期。看起来它真的只是在date_start列中选择最新的日期，考虑到它是2016-11-06，这是一个有效的date_start，但它超出了主要的查询BETWEEN ...

我对子查询非常可怕，所以我不确定我到底错在哪里：

SELECT 
    the_thresholds.client_id,
    the_thresholds.zipcode,
    ziplatlongs.county,
    ziplatlongs.city,
    ziplatlongs.stateabbr,
    the_thresholds.email,
    the_thresholds.threshold_snow AS snow_threshold,
    SUM(certifications.total_snow) AS rollingTotal,
    SUM(certifications.total_snow) >= the_thresholds.threshold_snow AS targetMet,
    IF(SUM(certifications.total_snow) >= the_thresholds.threshold_snow,
        MIN(certifications.date_start),
    0) AS dateMet
FROM
    `customer_settings`.`snowfall_thresholds` AS the_thresholds
        INNER JOIN
    `snowfall_certification`.`the_certifications` AS certifications ON `the_thresholds`.`zipcode` = `certifications`.`zipcode`
        INNER JOIN
    `zipcodes`.`ziplatlongs` AS ziplatlongs ON `the_thresholds`.`zipcode` = `ziplatlongs`.`zipcode`
WHERE
    DATE(`certifications`.`date_start`) BETWEEN '2015-10-01' AND '2016-05-31'
GROUP BY `the_thresholds`.`zipcode`

正如我所说的，它正在返回我期望的所有列，我只是无法将它放到达到阈值的正确dateMet。