在Access 2010中对不同的列进行计数并在多列中显示结果

Question

我对SQL和Ms Access数据库很陌生。 已经在线搜索了一些帖子，但仍然对DISTINCT COUNT函数感到困惑。

是否可以通过以下简单方法完成以下操作而无需创建多个查询或VBA代码（由于性能问题）？或者可以使用子查询，如果可以，请问如何完成？ 请真正感谢您的建议。

非常感谢和欢呼 贝利

表格：材料

结果如下：

Answer 1

MS Access不支持COUNT(DISTINCT)，所以这很棘手。一种方法使用子查询。我认为这会起作用：

select c.col0,
       (select count(*)
        from (select distinct m2.col1
              from material as m2
              where m2.col0 = c.col0
             ) as m2
       ) as dcol1,
       (select count(*)
        from (select distinct m2.col2
              from material as m2
              where m2.col0 = c.col0
             ) as m2
       ) as dcol2,
       (select count(*)
        from (select distinct m2.col3
              from material as m2
              where m2.col0 = c.col0
             ) as m2
       ) as dcol3
from (select distinct col0 from material) as c;

我不确定100％MS Access是否支持两个级别的关联子句。如果没有，您可以这样写：

select c.col0,
       (select count(*)
        from (select distinct m2.col0, m2.col1
              from material as m2
             ) as m2
        where m2.col0 = c.col0
       ) as dcol1,

但是第一个更好的将具有更好的性能。

编辑：

对于这些查询，您需要在(col0, col1)上建立索引。

Answer 2

这建议我将GROUP BY与COUNT(DISTINCT)一起简单使用：

SELECT Col0, COUNT(DISTINCT Col1) AS DCol1, 
       COUNT(DISTINCT Col2) AS DCol2, COUNT(DISTINCT Col3) AS DCol3
FROM table t
GROUP BY Col0;

DISTINCT COUNT不是FUNCTION，有两件事，一个是FUNCTION，它是COUNT()，另一个是DISTINCT，可以用于唯一性。

您还可以将其与SELECT语句一起使用，以使整个行变得唯一。

编辑：如果DISTINCT函数中的COUNT()不起作用，则使用相关方法：

select distinct c.col0,
       (select count(*)
        from (select distinct m1.col1
              from material as m1
              where m1.col0 = m.col0
             ) as m1
       ) as dcol1,
       (select count(*)
        from (select distinct m2.col2
              from material as m2
              where m2.col0 = m.col0
             ) as m2
       ) as dcol2,
       (select count(*)
        from (select distinct m3.col3
              from material as m3
              where m3.col0 = m.col0
             ) as m3
       ) as dcol3
from material as m;