SQL查询:串联的许多列字符串类型中的许多列

Question

假设我的表包含以下列

 Roll_number numeric           not null
 Subject1    varchar(40)       null
 Subject2    varchar(40)       null
 . . .
 Subject8    varchar(40)       null

我必须使用SQL查询在所有这些主题1到8中搜索一个主题。在所有这些列中搜索子字符串搜索的最佳查询是什么，请记住，其中任何一个都可以具有无效的值。

我写了

select * 
from students_data 
where subject1="BIOLOGY" or subject2="BIOLOGY" . . . . or subject8="BIOLOGY" 

但是我需要一个简单的查询，因为实际上我的表中有20列以上

查询

select * from table1 where "BIOLOGY" in (subject1,subject2,subject3)

在 " bio" 在该表字段

Answer 1

您可以像这样使用IN谓词：

SELECT * 
FROM students_data 
WHERE 'BIOLOGY' IN (subject1, subject2, . . . , subject8);

Answer 2

怎么样？

SELECT * 
FROM students_data
WHERE subject1 + ' ' + subject2 + ' ' + ..... + subject8 LIKE '%BIOLOGY%';

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更新1

对于 null 值，在下面使用。

SELECT * 
FROM students_data
WHERE ISNULL(subject1,'') + ' ' + ISNULL(subject2,'')
+ ' ' + ..... + ISNULL(subject8,'') LIKE '%BIOLOGY%';

用于使用Bio，您可以使用LIKE '%BIO%';

Answer 3

这可能不会更快，但我相信它更清楚。

首先创建标准化视图（您可以以这种方式存储数据 - 这是理想的）

Create View SubjectData AS
(
   SELECT Roll_number, 1 AS SubjectNumber, Subject1 AS Subject FROM TABLE1
   UNION ALL
   SELECT Roll_number, 2 AS SubjectNumber, Subject2 AS Subject FROM TABLE1
   UNION ALL
   SELECT Roll_number, 3 AS SubjectNumber, Subject3 AS Subject FROM TABLE1
   UNION ALL
   SELECT Roll_number, 4 AS SubjectNumber, Subject4 AS Subject FROM TABLE1
   UNION ALL
   SELECT Roll_number, 5 AS SubjectNumber, Subject5 AS Subject FROM TABLE1
   UNION ALL
   SELECT Roll_number, 6 AS SubjectNumber, Subject6 AS Subject FROM TABLE1
   UNION ALL
   SELECT Roll_number, 7 AS SubjectNumber, Subject7 AS Subject FROM TABLE1
   UNION ALL
   SELECT Roll_number, 8 AS SubjectNumber, Subject8 AS Subject FROM TABLE1
)

现在选择很简单：

SELECT Roll_number, SubjectNumber from SubjectData where CONTAINS(Subject,'Bio')

n.b。注意包含的使用，应更快地做。

我没有测试上述查询，它们可能具有错别字。

Answer 4

在这种情况下，

SELECT * 
FROM students_data
WHERE 
nvl(subject1,'') + ' ' + nvl(subject2,'') + ' ' + ..... + nvl(subject8,'') 
LIKE '%BIO%';

如果您的数据库不支持，则可以使用ifnull()或decode()