字段列表中的“条形码”列不明确

Question

SELECT barcode, t3.employee,
SEC_TO_TIME(SUM(TIMESTAMPDIFF(SECOND, dateandtime, (SELECT IFNULL(MIN(dateandtime),NOW())
                                                  FROM wwtlog b
                                                 WHERE b.barcode = a.barcode
                                                   AND b.dateandtime  > a.dateandtime
                                                   AND b.inorout = 'IN'
                                                )))) timeused
FROM wwtlog a
    JOIN (SELECT t1.barcode, t1.employee FROM wwtlog t1
  JOIN (SELECT barcode, MAX(id) id FROM wwtlog GROUP BY barcode) t2
ON t1.id = t2.id AND t1.barcode = t2.barcode) t3 ON t1.barcode = barcode
WHERE inorout = 'OUT' and barcode IN (SELECT t1.barcode FROM wwtlog t1
                                JOIN (SELECT barcode, MAX(dateandtime) dateandtime FROM wwtlog GROUP BY barcode) t2
                                ON t1.barcode = t2.barcode AND t1.dateandtime = t2.dateandtime WHERE inorout = 'IN')
GROUP BY barcode;

Any help on this would be fantastic, I started getting this when I added the join in to get t3.employee. I have a feeling that I don't know what I'm doing.

Im trying to get Unique Barcode, with the total time between time IN and time OUT time stamps. I was trying to use the join to get the employee that last had the item(barcode) checked out or in. if you take out the join for t3.employee, and just ask for employee, it gives me the first record employee for each barcode, not the last one.

Answer 1

You are using the column barcode but this column is present in several table try assign the table alias ar each barcode column

SELECT a.barcode, t3.employee,
SEC_TO_TIME(SUM(TIMESTAMPDIFF(SECOND, dateandtime, (SELECT IFNULL(MIN(dateandtime),NOW())
                                                  FROM wwtlog b
                                                 WHERE b.barcode = a.barcode
                                                   AND b.dateandtime  > a.dateandtime
                                                   AND b.inorout = 'IN'
                                                )))) timeused
FROM wwtlog a
    JOIN (SELECT t1.barcode, t1.employee FROM wwtlog t1
  JOIN (SELECT barcode, MAX(id) id FROM wwtlog GROUP BY barcode) t2
ON t1.id = t2.id AND t1.barcode = t2.barcode) t3 ON t1.barcode = a.barcode
WHERE inorout = 'OUT' and a.barcode IN (SELECT t1.barcode FROM wwtlog t1
                                JOIN (SELECT barcode, MAX(dateandtime) dateandtime FROM wwtlog GROUP BY barcode) t2
                                ON t1.barcode = t2.barcode AND t1.dateandtime = t2.dateandtime WHERE inorout = 'IN')
GROUP BY a.barcode;

expecially at the main table eg: wwtlog a

Answer 2

You're missing a table reference at ON t1.barcode = barcode. Since barcode column is in multiple tables it needs to be strictly identified so as not to be ambiguous.