我的 MySQL 查询 (UNION) 有什么问题？

Question

我希望你能把我带到这里。我正在使用 PMS 系统，我想运行一个简单的 SELECT 语句来根据客户的包裹到达和交易类型获取密码列表。 'transferConfirmation' table 已经有客户 ID 和密码并为每个实例显示一行但是由于某种原因，当我使用以下查询时：

SELECT `tc`.`transferID` AS `transferID`,
       `c`.`firstName` AS `firstName`,
       `c`.`lastName` AS `lastName`,
       `tc`.`secretCode` AS `secretCode`,
       'Purchase Order' AS `transactionType`
FROM (((((`db`.`transferconfirmation` `tc`
          JOIN `db`.`customer` `c` on((`tc`.`customerID` = `c`.`customerID`)))
         JOIN `db`.`transfer` `t` on((`t`.`transferID` = `tc`.`transferID`)))
        JOIN `db`.`transferentry` `te` on((`t`.`transferID` = `te`.`transferID`)))
       JOIN `db`.`purchaseorder` `po` on((`te`.`referenceID` = `po`.`purchaseOrderID`)))
      JOIN `db`.`purchaseorderentry` `poe` on(((`po`.`purchaseOrderID` = `poe`.`purchaseOrderID`)
                                               AND (`te`.`referenceEntryID` = `poe`.`purchaseOrderEntryID`))))
WHERE (`poe`.`collectionStatus` = 0)
UNION ALL
SELECT `tc`.`transferID` AS `transferID`,
       `c`.`firstName` AS `firstName`,
       `c`.`lastName` AS `lastName`,
       `tc`.`secretCode` AS `secretCode`,
       'Shipping Order' AS `transactionType`
FROM (((((`db`.`transferconfirmation` `tc`
          JOIN `db`.`customer` `c` on((`tc`.`customerID` = `c`.`customerID`)))
         JOIN `db`.`transfer` `t` on((`t`.`transferID` = `tc`.`transferID`)))
        JOIN `db`.`transferentry` `te` on((`t`.`transferID` = `te`.`transferID`)))
       JOIN `db`.`shippingorder` `so` on((`te`.`referenceID` = `so`.`shippingOrderID`)))
      JOIN `db`.`shippingorderentry` `soe` on(((`so`.`shippingOrderID` = `soe`.`shippingOrderID`)
                                               AND (`te`.`referenceEntryID` = `soe`.`shippingOrderEntryID`))))
WHERE (`soe`.`collectionstatus` = 0)

我不断得到重复数据的结果，唯一不同的是交易。我想我的问题是，如果密码已被选择一次，我如何防止任何其他行显示相同的代码。

Answer 1

使用 UNION 运算符。 UNION 运算符将从每个查询中删除重复记录（UNION ALL 会保留它们）。

SELECT transferID, firstName, lastName, secretCode,
    'Purchase Order' AS transactionType
FROM ...
UNION
SELECT transferID, firstName, lastName, secretCode,
    'Purchase Order' AS transactionType
FROM ...

我的 MySQL 查询 (UNION) 有什么问题？

What is wrong with my MySQL query (UNION)?

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