具有计算列类型的SQL视图变为可为空

Question

I have got a sql table view where one of the columns is calculated: 0.1 * [column_name] where [column_name] is of type Decimal not NULL .

Received view field becomes Decimal NULL because of some reason.

Why NOT NULL changes to NULL ?

Regards Mariusz

Answer 1

You can force it back to being not null by wrapping it in an ISNULL:

create table T (
    Value decimal(38,12) not null
)
go
create view V1
as
    select 0.1 * Value as Value from T
go
create view V2
as
    select ISNULL(0.1 * Value,0) as Value from T
go

V1's value column is marked as nullable, V2's isn't. Strangely, this is one place where you can't use the more standards compliant COALESCE :

create view V3
as
    select COALESCE(0.1 * Value,0) as Value from T
go

V3 resembles V1.

Answer 2

您忘记了发布代码，但这可能是因为左联接或右联接找不到匹配的行...