SQL 查询 return 列值的实例但 return 附加字段

Question

我在 table 中有多个地段。这些批次通常出现一次，但可以重复。我想获取具有最早创建日期（列）的特定产品代码（列）的每个批次，带回与该批次相关的其他字段（到期日、仓库等）。

到目前为止，我有以下查询：

SELECT DISTINCT lot_number, prod_code, date_received, expiry_date, quantity 
FROM scheme.stquem  
WHERE prod_code = '001'  
AND lot_number != ''     //removes blanks   
ORDER BY lot_number

如何通过选择最早收到日期的批次来删除重复项？

Answer 1

使用group by和join:

SELECT s.lot_number, s.prod_code, s.date_received, s.expiry_date, s.quantity 
FROM scheme.stquem s JOIN
     (SELECT lot_number, min(date_received) as mindr
      FROM scheme.stquem
      WHERE prod_code = '001' AND lot_number <> ''     //removes blanks   
      GROUP BY lot_number
     ) sl
     ON sl.lot_number = s.lot_number and sl.mindr = s.date_received 
WHERE prod_code = '001'
ORDER BY s.lot_number;

Answer 2

仅当没有其他具有相同 prod_code 但更早日期的行时，才将 NOT EXISTS 用于 return 行：

SELECT lot_number, prod_code, date_received, expiry_date, quantity 
FROM scheme.stquem st1
WHERE prod_code = '001'  
AND lot_number != ''     //removes blanks   
AND NOT EXISTS (select 1 from scheme.stquem st2
                where st1.prod_code = st2.prod_code
                  and st2.date_received < st1.date_received)
ORDER BY lot_number

SQL 查询 return 列值的实例但 return 附加字段

SQL Query to return the instance of a column value but return additional fields

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