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

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;

其他回答

如果我理解正确,你想在一个列中计数所有NULL和所有NOT NULL…

如果是正确的:

SELECT count(*) FROM us WHERE a IS NULL 
UNION ALL
SELECT count(*) FROM us WHERE a IS NOT NULL

阅读评论后,编辑了完整的查询:]


SELECT COUNT(*), 'null_tally' AS narrative 
  FROM us 
 WHERE a IS NULL 
UNION
SELECT COUNT(*), 'not_null_tally' AS narrative 
  FROM us 
 WHERE a IS NOT NULL;

在我的例子中,我想要多列之间的“空分布”:

SELECT
       (CASE WHEN a IS NULL THEN 'NULL' ELSE 'NOT-NULL' END) AS a_null,
       (CASE WHEN b IS NULL THEN 'NULL' ELSE 'NOT-NULL' END) AS b_null,
       (CASE WHEN c IS NULL THEN 'NULL' ELSE 'NOT-NULL' END) AS c_null,
       ...
       count(*)
FROM us
GROUP BY 1, 2, 3,...
ORDER BY 1, 2, 3,...

根据“……它可以很容易地扩展到更多的列,只要需要

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')

如果是mysql,你可以尝试这样做。

select 
   (select count(*) from TABLENAME WHERE a = 'null') as total_null, 
   (select count(*) from TABLENAME WHERE a != 'null') as total_not_null
FROM TABLENAME

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)