用于计数非空值

select count(*) from us where a is not null;

用于计算空值

 select count(*) from us where a is null;

用于计数非空值

select count(*) from us where a is not null;

用于计算空值

 select count(*) from us where a is null;

我有一个类似的问题:要计算所有不同的值，空值也算作1。简单的计数在这种情况下不起作用，因为它不考虑空值。

下面是一个适用于SQL的代码片段，不涉及选择新值。 基本上，执行distinct后，还使用row_number()函数返回新列(n)中的行号，然后对该列执行计数:

SELECT COUNT(n)
FROM (
    SELECT *, row_number() OVER (ORDER BY [MyColumn] ASC) n
    FROM (
        SELECT DISTINCT [MyColumn]
                    FROM [MyTable]
        ) items  
) distinctItems

试试这个. .

SELECT CASE 
         WHEN a IS NULL THEN 'Null' 
         ELSE 'Not Null' 
       END a, 
       Count(1) 
FROM   us 
GROUP  BY CASE 
            WHEN a IS NULL THEN 'Null' 
            ELSE 'Not Null' 
          END 

SELECT SUM(NULLs) AS 'NULLS', SUM(NOTNULLs) AS 'NOTNULLs' FROM 
    (select count(*) AS 'NULLs', 0 as 'NOTNULLs' FROM us WHERE a is null
    UNION select 0 as 'NULLs', count(*) AS 'NOTNULLs' FROM us WHERE a is not null) AS x

这很糟糕，但它将返回一个带有2个cols的记录，指示null和非null的计数。

以防你想把它记录在一条记录里:

select 
  (select count(*) from tbl where colName is null) Nulls,
  (select count(*) from tbl where colName is not null) NonNulls 

;-)