查看表的前两条记录时的SQL查询

我有一个用于工资/费率历史记录的员工表。看起来

Employee# EffectDate Salary 00016 2014-01-03 78100.00 00016 2013-07-03 75130.00 00016 2013-01-06 72140.00 00114 2014-07-15 85610.00 00244 2014-01-10 54130.00 00244 2013-06-30 50140.00 00634 2013-12-25 72560.00 00634 2013-04-05 69348.00 00634 2012-01-01 64530.00 我正在尝试为员工获取一行，显示当前工资、上次生效日期和最近一次工资

Employee# CurrentSalary LastChange PreviousSalary 00016 78100.00 2014-01-03 75130.00 00114 85610.00 2014-07-15 NULL 00244 54130.00 2014-01-10 50140.00 00634 72560.00 2013-12-25 69348.00

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使用Microsoft SQL 2012，从我的头顶快速变型：

select
    t.Employee,
    (select top 1 Salary
        from table as a
        where a.Employee = t.Employee and a.EffectDate = t.LastChange
        order by EffectDate desc) as CurrentSalary,
    t.LastChange,
    (select top 1 Salary
        from table as a
        where a.Employee = t.Employee and a.EffectDate < t.LastChange
        order by EffectDate desc) as PreviousSalary
from (
    select Employee, max(EffectDate) as LastChange
    from table
    group by Employee) as t

这里有一种方法将行数与max和case一起使用，这是一种旋转形式：

with cte as (
  select *,
    row_number() over (partition by employeenum order by effectdate desc) rn
  from salary
  )
select employeenum,
  max(case when rn = 1 then salary end) currentsalary,
  max(case when rn = 1 then effectdate end) lastchange,
  max(case when rn = 2 then salary end) previoussalary
from cte
group by employeenum

试试这个，使用CTE，您可以通过分区然后在查询中使用这个行号来获得一个行号

DECLARE @tbl TABLE (
    EmployeeId    VARCHAR (20)  ,
    EffectiveDate DATE          ,
    salary        DECIMAL (8, 2));

INSERT  INTO @tbl (EmployeeId, EffectiveDate, salary)
VALUES           (00016, getdate(), 7852.00);

INSERT  INTO @tbl (EmployeeId, EffectiveDate, salary)
VALUES           (00016, getdate() + 1, 7952.00);

INSERT  INTO @tbl (EmployeeId, EffectiveDate, salary)
VALUES           (00016, getdate() + 2, 8052.00);

INSERT  INTO @tbl (EmployeeId, EffectiveDate, salary)
VALUES           (00017, getdate(), 7852.00);

INSERT  INTO @tbl (EmployeeId, EffectiveDate, salary)
VALUES           (00017, getdate() + 1, 7952.00);

INSERT  INTO @tbl (EmployeeId, EffectiveDate, salary)
VALUES           (00018, getdate(), 7852.00);

WITH   cteSalary
AS     (SELECT EmployeeId,
               EffectiveDate,
               salary,
               ROW_NUMBER() OVER (PARTITION BY EmployeeId 
                              ORDER BY EffectiveDate DESC) AS rn
        FROM   @tbl)
SELECT a.EmployeeId,
       a.EffectiveDate,
       a.salary,
       b.salary AS 'Previous salary'
FROM   cteSalary AS a
       LEFT OUTER JOIN
       cteSalary AS b
       ON a.EmployeeId = b.EmployeeId
          AND b.rn = 2
WHERE  a.rn = 1;

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您是否要求我们为您编写SQL查询？您尝试过哪些代码？这不是一个代码外包社区。为什么你反对根据你的评论进行聚合？多个相关子查询肯定比单个聚合子查询慢。谢谢。简单，可以在我当前的SQL查询中对表进行分区。带有AND子句的SELECTTOP1是我出错的地方。再次感谢！