The field value in SQL Server cannot be empty

Environment: sqlserver 2008

Create a test table and add two fields. Field A is set to the primary key, which is not empty and unique. Field B is not restricted.

 

Execute insert into test values ('', 'A'), but the execution is successful.

The record can be queried. Field A does not have a value.

 

I am a bit confused. I will test the insert into test values (null, 'A') again.

Tip:

Primary error 0x80004005, secondary error 25005
> Insert into test values (null, 'A ')
The column cannot contain null values. [Column name = A, table name = test]

 

It turns out that the concept of not null in sqlserver can only be null, which is quite different from that in Oracle. Please note that!