時間戳..只需要第一個和最後一個

Question

我有一個查詢返回估計的日期和時間戳。每個估算可以有多個時間戳。我只需要第一張和最後一張郵票。我怎樣才能做到這一點？我的查詢是這樣的：

SELECT LogDateTime, Operator, Program, Explanation, TransactionCode 
FROM SystemLog 
WHERE Program = 'Estimating' 
ORDER BY TransactionCode 

Answer 1

使用min()和max()聚合函數：

SELECT 
    min(LogDateTime) as first_LogDateTime, 
    max(LogDateTime) as last_LogDateTime, 
    Operator, Program, Explanation, TransactionCode 
FROM SystemLog 
WHERE Program = 'Estimating' 
GROUP BY Operator, Program, Explanation, TransactionCode 
ORDER BY TransactionCode