Question

如何删除查询中的NULL单元格，因为即使CompanyName不存在，也会出现一些记录？

SELECT ClientID, CompanyName, FirstName, LastName, Street, City
  FROM Client
  WHERE CompanyName LIKE '%G%' Or FirstName LIKE '%J%' OR LastName LIKE '%J%'
  OR Street LIKE '%J%' OR City LIKE '%J%' Or ContactNo LIKE '%0%'
  AND ClientTypeID = 2

Answer 1

要排除CompanyName为null的所有行，您需要添加

AND CompanyName is NOT NULL

您可能需要在WHERE之后和最后OR条件之后使用括号

Answer 2

天真地，只需使用

SELECT ClientID, CompanyName, FirstName, LastName, Street, City
FROM Client
WHERE CompanyName is not NULL and (CompanyName LIKE '%G%' Or FirstName LIKE '%J%' Or LastName LIKE '%J%' Or Street LIKE '%J%' Or City LIKE '%J%' Or ContactNo LIKE '%0%'
AND ClientTypeID = 2)

Answer 3

CompanyName like '%G'

如果CompanyName为null，

将失败，不是吗？

如果您的数据库不是那样，只需添加

即可

AND CompanyName IS NOT NULL

Answer 4

SELECT ClientID, CompanyName, FirstName, LastName, Street, City
FROM Client
WHERE (CompanyName LIKE '%G%' Or FirstName LIKE '%J%' Or LastName LIKE '%J%' Or Street LIKE '%J%' Or City LIKE '%J%' Or ContactNo LIKE '%0%' AND ClientTypeID = 2) AND CompanyName IS NOT NULL;

问题是你有或有陈述。即使CompanyName不适合，LastName也可能适合。因为您在过滤结果中使用或将包括在内。

你正在混合或者是，并且两者都没有任何括号。你不应该这样做。你应该写一下：

SELECT ClientID, CompanyName, FirstName, LastName, Street, City
FROM Client
WHERE (CompanyName LIKE '%G%' Or FirstName LIKE '%J%' Or LastName LIKE '%J%' Or Street LIKE '%J%' Or City LIKE '%J%' Or ContactNo LIKE '%0%') AND ClientTypeID = 2;

或

SELECT ClientID, CompanyName, FirstName, LastName, Street, City
FROM Client
WHERE CompanyName LIKE '%G%' Or FirstName LIKE '%J%' Or LastName LIKE '%J%' Or Street LIKE '%J%' Or City LIKE '%J%' Or (ContactNo LIKE '%0%' AND ClientTypeID = 2);

Answer 5

从所有列中删除所有空值

declare @ex as nvarchar(max) = ''
declare @_null as nvarchar(max)
set @_null = ''

select @_null += 'isnull(' + QUOTENAME(column_name) + ',0) as ' + QUOTENAME(column_name) + ','

from sample.INFORMATION_SCHEMA.columns where TABLE_NAME = 'table';

set @_null = left(@_null,len(@_null) - 1);

set @ex = 'select ' + @_null + ' from table';

exec sp_executesql @ex;

如何删除具有NULL值的列？

5 个答案: