我有一张桌子

create table us
(
 a number
);

现在我有如下数据:

a
1
2
3
4
null
null
null
8
9

现在我需要一个查询来计算列a中的空值和非空值


当前回答

为了提供另一种选择,Postgres 9.4+允许对聚合应用FILTER:

SELECT
  COUNT(*) FILTER (WHERE a IS NULL) count_nulls,
  COUNT(*) FILTER (WHERE a IS NOT NULL) count_not_nulls
FROM us;

SQLFiddle: http://sqlfiddle.com/ # !17/80a24/5

其他回答

这在T-SQL中有效。如果你只是计算一些东西的数量,你想包括空值,使用COALESCE而不是case。

IF OBJECT_ID('tempdb..#us') IS NOT NULL
    DROP TABLE #us

CREATE TABLE #us
    (
    a INT NULL
    );

INSERT INTO #us VALUES (1),(2),(3),(4),(NULL),(NULL),(NULL),(8),(9)

SELECT * FROM #us

SELECT CASE WHEN a IS NULL THEN 'NULL' ELSE 'NON-NULL' END AS 'NULL?',
        COUNT(CASE WHEN a IS NULL THEN 'NULL' ELSE 'NON-NULL' END) AS 'Count'
    FROM #us
    GROUP BY CASE WHEN a IS NULL THEN 'NULL' ELSE 'NON-NULL' END

SELECT COALESCE(CAST(a AS NVARCHAR),'NULL') AS a,
        COUNT(COALESCE(CAST(a AS NVARCHAR),'NULL')) AS 'Count'
    FROM #us
    GROUP BY COALESCE(CAST(a AS NVARCHAR),'NULL')
select count(isnull(NullableColumn,-1))

正如我理解你的查询,你只需要运行这个脚本并获得Total Null,Total NotNull行,

select count(*) - count(a) as 'Null', count(a) as 'Not Null' from us;

这适用于Oracle和SQL Server(你可能可以让它在其他RDBMS上工作):

select sum(case when a is null then 1 else 0 end) count_nulls
     , count(a) count_not_nulls 
  from us;

Or:

select count(*) - count(a), count(a) from us;

如果你正在使用MS Sql Server…

SELECT COUNT(0) AS 'Null_ColumnA_Records',
(
    SELECT COUNT(0)
    FROM your_table
    WHERE ColumnA IS NOT NULL
) AS 'NOT_Null_ColumnA_Records'
FROM your_table
WHERE ColumnA IS NULL;

我不建议你这么做……但这里你有它(在同一张表中的结果)