SQL 汇总计数显示总计为 NULL

Question

我需要知道如何用总数替换 NULL。

这是我使用 ROLLUP 查询的副本。

SELECT    DATEPART(YEAR, study_date) AS 'Year',
          COUNT(distinct study_uid) AS 'Studies'
FROM local_studies
GROUP BY rollup (DATEPART(YEAR, study_date))
ORDER BY  'Year' DESC

这是输出：

  Year  Studies
2020    497
2019    165743
2018    165043
2017    182712
2016    210700
2015    219373
2014    214097
2013    211566
2012    212900
2011    217957
2010    213542
2009    193510
2008    95434
2007    53722
2006    44422
2005    12119
2004    129
2003    65
2000    4
NULL    2413535

我喜欢用 'Total' 替换“NULL”值：（如下所示）

  Year  Studies
2020    497
2019    165743
2018    165043
2017    182712
2016    210700
2015    219373
2014    214097
2013    211566
2012    212900
2011    217957
2010    213542
2009    193510
2008    95434
2007    53722
2006    44422
2005    12119
2004    129
2003    65
2000    4
Total   2413535

任何将 NULL 转换为单词 TOTAL 的建议都将不胜感激。

Answer 1

我一般只用coalesce():

SELECT COALESCE(DATENAME(YEAR, study_date), 'Total') AS Year,
       COUNT(distinct study_uid) AS 'Studies'
FROM local_studies
GROUP BY rollup (DATENAME(YEAR, study_date))
ORDER BY Year DESC;

请注意，这将切换为使用 DATENAME()，因此该列是字符串而不是数字。

此外，如果值可能是 NULL，则效果不佳。为此，有 GROUPING() 函数。

Answer 2

SELECT    CASE GROUPING_ID(DATEPART(YEAR, study_date)) WHEN 1 THEN 'Total' ELSE CAST(DATEPART(YEAR, study_date) AS VARCHAR(10)) END AS 'Year',
          COUNT(distinct study_uid) AS 'Studies'
FROM local_studies
GROUP BY rollup (DATEPART(YEAR, study_date))
ORDER BY  GROUPING_ID(DATEPART(YEAR, study_date)), 'Year' DESC;

SQL 汇总计数显示总计为 NULL

SQL Count with rollup shows totals as NULL

sql

sql-server

rollup