多列多計數

Question

我是sql新手。 我想數一數：

Select count(*) from table where col1= x and col2=x and Col3=x. 

我需要在所有不同的列中計數相同的值。 任何幫助將不勝感激。

Answer 1

您可以使用條件聚合：

Select sum(case when col1='x' then 1 else 0 end) as count_col1,
       sum(case when col2='x' then 1 else 0 end) as count_col2,
       sum(case when col3='x' then 1 else 0 end) as count_col3
  from tab;

如果要具有這些計數值的總和，請將上述查詢視為內部查詢，並使用以下方法：

 Select q.*,
        q.count_col1 + q.count_col2 + q.count_col3 whole_sum
   from     
     (
        Select sum(case when col1='x' then 1 else 0 end) as count_col1,
               sum(case when col2='x' then 1 else 0 end) as count_col2,
               sum(case when col3='x' then 1 else 0 end) as count_col3
          from tab  
      ) q

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