Question

我有一张这样的桌子。

id ___ d1 ___ d2 ___ d3 ___ d4 ___ d5 ___ d6 ___ d7 ___ d8
----------------------------------------------------------
01 ___ XX ___ "" ___ "" ___ "" ___ "" ___ "" ___ "" ___ "" (There are 7 ""s)
02 ___ XX ___ XX ___ XX ___ "" ___ "" ___ "" ___ "" ___ "" (There are 5 ""s)
03 ___ XX ___ XX ___ "" ___ "" ___ "" ___ "" ___ "" ___ "" (There are 6 ""s)
04 ___ XX ___ "" ___ "" ___ "" ___ "" ___ "" ___ "" ___ "" (There are 7 ""s)

我希望看到这样的输出：

id ___ count
------------
01 ___ 7
02 ___ 5
03 ___ 6
04 ___ 7

我该怎么做？简单地说，我想计算空字符串，但在同一行。

Answer 1

您可以使用case语句，并将结果加起来：

SELECT
    id
,   (    CASE d1 WHEN '' THEN 1 ELSE 0 END
    +    CASE d2 WHEN '' THEN 1 ELSE 0 END
    +    CASE d3 WHEN '' THEN 1 ELSE 0 END
    +    CASE d4 WHEN '' THEN 1 ELSE 0 END
    +    CASE d5 WHEN '' THEN 1 ELSE 0 END
    +    CASE d6 WHEN '' THEN 1 ELSE 0 END
    +    CASE d7 WHEN '' THEN 1 ELSE 0 END
    +    CASE d7 WHEN '' THEN 1 ELSE 0 END
    ) as TotalSpaces
FROM myTable

Answer 2

我倾向于使用将布尔值视为整数的MySQL快捷方式：

select id,
       ((d1 = '') + (d2 = '') + (d3 = '') + (d4 = '') + (d5 = '') +
        (d6 = '') + (d7 = '') + (d8 = '')
       ) as "Count"
from table t;

伯爵＆＃34;＆＃34;同一行上的（空字符串）

2 个答案: