使用 T-SQL 从 SQL 服务器获取最旧的记录

Question

I have a T-SQL query where I need to find the oldest date record. I have written it like this:

SELECT
    T0.ItemCode, T0.OpenQty AS 'Qty', MIN(T1.DocDate) AS 'DocDate', 
    T1.DocNum, T1.CardCode, T1.SlpCode AS 'Sales Person', T0.WhsCode
FROM
    RDR1 T0
INNER JOIN
    ORDR T1 ON T0.DocEntry = T1.DocEntry
WHERE 
    T0.linestatus = 'O'
GROUP BY 
    T0.ItemCode, T0.OpenQty , T1.DocNum, T1.CardCode, T1.SlpCode , T0.WhsCode

but it is not returning the oldest date record.

Data is shown in this screenshot:

Answer 1

You can use ROW_NUMBER() to rank the records by ascending T1.DocDate in a inner query, and then select the oldest in the outer query:

Select *
From (
    Select  
        T0.ItemCode, 
        T0.OpenQty as 'Qty', 
        T1.DocDate,
        T1.DocNum, 
        T1.CardCode, 
        T1.SlpCode as 'Sales Person', 
        T0.WhsCode,
        Row_Number() Over(Order By T1.DocDate) rn
    From RDR1 T0
    Inner Join ORDR T1 on T0.DocEntry = T1.DocEntry
    Where T0.linestatus = 'O'
) x
Where rn = 1

This will give you the oldest record in the table. If you need to get the oldest record per group, then you can add a PARTITION BY clause to the ROW_NUMBER() function.

Note: this also assumes that T1.DocDate is of a date-like datatype, which seems to be (and should be) the case by looking at your sample data.

Answer 2

Why are you writing Self join? If you need to get 10 oldest record from table then just sort the table according date in ascending order and list top 10 rows.

For Example -

Select  top 10 T0.ItemCode, T0.OpenQty as 'Qty', T1.DocDate as 'DocDate', T1.DocNum, T1.CardCode, T1.SlpCode as 'Sales Person', T0.WhsCode
From RDR1 T0
Where T0.linestatus = 'O'
order by T1.DocDate