数据库环境:SQL SERVER 2005

  有时候,想将查询查询数来的数据格式化一下,不希望显示NULL值,或者复制表的数据时,被插入的表不允许有NULL。

我们可以通过ISNULL()函数或者COALESCE()函数对数据进行转换。

  如果要转换的字段太多,不想一个个字段去转,是否有什么办法批量转换NULL值呢?

  实现思路:

  我们通过系统表sys.all_columns关联sys.types表找到某个表的所有字段及其类型,如果该字段是允许NULL的,则进行转换。

转换规则:如果是数值类型,则将NULL转换成0,否则,转换成空字符串。

  下面是SQL实现,已经将它封装到表变量中,需要的时候直接传个表名进去调用即可。

ALTER FUNCTION [dbo].[f_null_cast]
(
@table_name VARCHAR(20)--表名
)
RETURNS VARCHAR(MAX)
AS
BEGIN
DECLARE @sql_text VARCHAR(MAX);
WITH x0
AS ( SELECT TOP 200 ','
+ CASE WHEN c.is_nullable = 0 THEN c.name
WHEN t.name IN ( 'smallint', 'int',
'decimal' )
THEN 'ISNULL(' + c.name + ',0) as '
+ c.name
ELSE 'ISNULL(' + c.name
+ ','''') as ' + c.name
END AS name_column
FROM sys.all_columns AS c ,
sys.types AS t
WHERE c.system_type_id = t.system_type_id
AND t.name <> 'sysname'
AND c.object_id = OBJECT_ID(@table_name)
ORDER BY c.column_id--根据字段创建的先后顺序排序
)
SELECT @sql_text = 'select ' + STUFF(( SELECT name_column + ''
FROM x0
FOR
XML PATH('')
), 1, 1, '') + ' from '
+ @table_name
RETURN @sql_text END

  有一张testdemo表,表结构的定义语句如图1:

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" alt="" />

  执行SQL语句 “SELECT dbo.f_null_cast('testdemo') AS sql_text”,得到转换的结果如图2,图2的SQL是我用格式化工具

调整格式后的结果。

aaarticlea/png;base64,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" alt="" />

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