Mysql SQL来获取同一列中不同日期的值的差异

如何获得特定日期特定列的值与上一日期相同列的值之间的差异

Current Table:
Date          Qty
8-Jan-17      100
9-Jan-17      120
10-Jan-17     180

Desired Output:

Date         Diff Qty
9-Jan-17      20
10-Jan-17     60

---

假设日期不重复，并且两者之间也没有间隔，这将起作用

    --Sample data as provided. This script works in SQL Server 2005+
    CREATE TABLE #Table1
        ([Date] datetime, [Qty] int)
    ;

    INSERT INTO #Table1
        ([Date], [Qty])
    VALUES
        ('2017-01-08 00:00:00', 100),
        ('2017-01-09 00:00:00', 120),
        ('2017-01-10 00:00:00', 180)
    ;

   --This script is plain SQL for any DMBS 

   select y.Date, y.Qty-x.Qty as 'Diff Qty'
   from #table1 x inner join #Table1 y 
     on x.Date+1=y.Date

结果

+-------------------------+----------+
|          Date           | Diff Qty |
+-------------------------+----------+
| 2017-01-09 00:00:00.000 |       20 |
| 2017-01-10 00:00:00.000 |       60 |
+-------------------------+----------+

---

假设日期不重复，并且两者之间也没有间隔，这将起作用

    --Sample data as provided. This script works in SQL Server 2005+
    CREATE TABLE #Table1
        ([Date] datetime, [Qty] int)
    ;

    INSERT INTO #Table1
        ([Date], [Qty])
    VALUES
        ('2017-01-08 00:00:00', 100),
        ('2017-01-09 00:00:00', 120),
        ('2017-01-10 00:00:00', 180)
    ;

   --This script is plain SQL for any DMBS 

   select y.Date, y.Qty-x.Qty as 'Diff Qty'
   from #table1 x inner join #Table1 y 
     on x.Date+1=y.Date

结果

+-------------------------+----------+
|          Date           | Diff Qty |
+-------------------------+----------+
| 2017-01-09 00:00:00.000 |       20 |
| 2017-01-10 00:00:00.000 |       60 |
+-------------------------+----------+

---

你到底在使用哪种数据库管理系统？你有身份栏吗？你的约会总是连续的吗？没有重复也没有遗漏日期？您使用的是哪种DBMS？你有身份栏吗？你的约会总是连续的吗？没有重复也没有错过的一天？