SQL 获取最近的日期答案

【问题标题】：SQL Get Most Recent DateSQL 获取最近的日期
【发布时间】：2015-05-22 04:58:43
【问题描述】：

我希望有人可以帮助我。我不太擅长 SQL。我看过无数其他帖子，只是无法弄清楚。我有以下数据，需要获取最近的日期。那将是 1993 年 9 月 1 日。

524 | David | NULL | 1991 | 01 | H | 1991-07-01 00:00:00.000

524 | David | NULL | 1992 | 01 | H | 1992-07-01 00:00:00.000

524 | David | NULL | 1993 | 09 | H | 1993-09-01 00:00:00.000

我尝试了以下查询，但没有返回任何结果。谁能告诉我我做错了什么？

SELECT student_crs_hist.id_num,   
     name_format_view.last_first_middle_suf,   
     year_term_table.pesc_session_type,   
     student_crs_hist.yr_cde,   
     student_crs_hist.trm_cde, 
     student_crs_hist.TRANSACTION_STS,
     year_term_table.TRM_BEGIN_DTE
   FROM student_crs_hist,   
     name_format_view,   
     year_term_table
   WHERE  
   student_crs_hist.id_num = name_format_view.id_num
     and student_crs_hist.yr_cde = year_term_table.yr_cde 
     and student_crs_hist.trm_cde = year_term_table.trm_cde 
     and student_crs_hist.TRANSACTION_STS <> 'D' 
     and student_crs_hist.id_num = 524
     and year_term_table.TRM_BEGIN_DTE = (select max(year_term_table.TRM_BEGIN_DTE) from year_term_table)
Group By
     student_crs_hist.id_num,   
     name_format_view.last_first_middle_suf,   
     year_term_table.pesc_session_type,   
     student_crs_hist.yr_cde,   
     student_crs_hist.trm_cde, 
     student_crs_hist.TRANSACTION_STS, 
     year_term_table.TRM_BEGIN_DTE

【问题讨论】：

标签： sql sql-server max

【解决方案1】：

您可能想要最高日期，但也需要所有其他列。

为此，您需要一个窗口聚合函数：

SELECT *
FROM 
 (
   SELECT student_crs_hist.id_num,   
        name_format_view.last_first_middle_suf,   
        year_term_table.pesc_session_type,   
        student_crs_hist.yr_cde,   
        student_crs_hist.trm_cde, 
        student_crs_hist.TRANSACTION_STS,
        year_term_table.TRM_BEGIN_DTE,
    -- group maximum = maximum date per id_num
        MAX(TRM_BEGIN_DTE) OVER (PARTITION BY student_crs_hist.id_num) AS maxDate
      FROM student_crs_hist,   
        name_format_view,   
        year_term_table
      WHERE  
      student_crs_hist.id_num = name_format_view.id_num
        AND student_crs_hist.yr_cde = year_term_table.yr_cde 
        AND student_crs_hist.trm_cde = year_term_table.trm_cde 
        AND student_crs_hist.TRANSACTION_STS <> 'D' 
        AND student_crs_hist.id_num = 524
 ) AS dt
WHERE TRM_BEGIN_DTE = maxDate  -- only the rows with the maximum date

【讨论】：

【解决方案2】：

    SELECT student_crs_hist.id_num,   
     name_format_view.last_first_middle_suf,   
     year_term_table.pesc_session_type,   
     student_crs_hist.yr_cde,   
     student_crs_hist.trm_cde, 
     student_crs_hist.TRANSACTION_STS,
     year_term_table.TRM_BEGIN_DTE
   FROM student_crs_hist,   
     name_format_view,   
     year_term_table
   JOIN (
       SELECT student_crs_hist.id_num, MAX(year_term_table.TRM_BEGIN_DTE) AS MaxDate
       FROM student_crs_hist,   
         name_format_view,   
         year_term_table
       WHERE  
       student_crs_hist.id_num = name_format_view.id_num
         and student_crs_hist.yr_cde = year_term_table.yr_cde 
         and student_crs_hist.trm_cde = year_term_table.trm_cde 
         and student_crs_hist.TRANSACTION_STS <> 'D' 
         and student_crs_hist.id_num = 524
         and year_term_table.TRM_BEGIN_DTE = (select max(year_term_table.TRM_BEGIN_DTE) from year_term_table)
       GROUP BY student_crs_hist.id_num
   ) MaxDateJoin ON student_crs_hist.id_num = MaxDateJoin.id_num AND year_term_table.TRM_BEGIN_DT = MaxDateJoin.MaxDate
   WHERE  
   student_crs_hist.id_num = name_format_view.id_num
     and student_crs_hist.yr_cde = year_term_table.yr_cde 
     and student_crs_hist.trm_cde = year_term_table.trm_cde 
     and student_crs_hist.TRANSACTION_STS <> 'D' 
     and student_crs_hist.id_num = 524
     and year_term_table.TRM_BEGIN_DTE = (select max(year_term_table.TRM_BEGIN_DTE) from year_term_table)
Group By
     student_crs_hist.id_num,   
     name_format_view.last_first_middle_suf,   
     year_term_table.pesc_session_type,   
     student_crs_hist.yr_cde,   
     student_crs_hist.trm_cde, 
     student_crs_hist.TRANSACTION_STS, 
     year_term_table.TRM_BEGIN_DTE

【讨论】：

我试图通过在 select 语句中执行 max(year_term_table.TRM_BEGIN_DTE) 将其合并到我的查询中，但它会带回所有记录。我的其他 SQL 是否有问题？
我认为问题是您按 year_term_table.TRM_BEGIN_DTE 分组，因此它将返回每个日期的记录。尝试更新版本，它应该返回每个 id_num 的一条记录和最大日期。

【解决方案3】：

对于在同一 id_num 中没有相同值的列，您需要使用 MAX 函数：

SELECT student_crs_hist.id_num
    ,name_format_view.last_first_middle_suf
    ,year_term_table.pesc_session_type
    ,max(student_crs_hist.yr_cde)
    ,max(student_crs_hist.trm_cde)
    ,student_crs_hist.TRANSACTION_STS
    ,max(year_term_table.TRM_BEGIN_DTE)
FROM student_crs_hist
    ,name_format_view
    ,year_term_table
WHERE student_crs_hist.id_num = name_format_view.id_num
    AND student_crs_hist.yr_cde = year_term_table.yr_cde
    AND student_crs_hist.trm_cde = year_term_table.trm_cde
    AND student_crs_hist.TRANSACTION_STS <> 'D'
    AND student_crs_hist.id_num = 524
    AND year_term_table.TRM_BEGIN_DTE = (
        SELECT max(year_term_table.TRM_BEGIN_DTE)
        FROM year_term_table
        )
GROUP BY student_crs_hist.id_num
    ,name_format_view.last_first_middle_suf
    ,year_term_table.pesc_session_type
    ,student_crs_hist.TRANSACTION_STS

【讨论】：