January 19, 2004 at 3:55 am
Hi All . I had a strange experience with composite primary key in table . In that I found if Type of the column is set to char then , it allows null values while updation; but it dosent alow it in case of inserts.I opened the data window in Enterprise manager where I discovered this . I am using sql7.0 Please comment
January 19, 2004 at 4:57 am
My guess,
you have a table with nullable columns that you use with a unique index.
A primary key constraint cannot be defined on nullable columns.
With a unique index, you can insert/update one (1) row with nulls in one of the columns of the unique index.
CREATE TABLE [T_test] (
[col1] [int] NULL ,
[col2] [char] (3) NULL ,
[col3] [varchar] (50) NULL ,
) ON [PRIMARY]
GO
alter table [T_test]
add CONSTRAINT [PK_T_alzdba] PRIMARY KEY CLUSTERED
(
[col1],
[col2]
) ON [PRIMARY]
go
-- errormessage :
-- Server: Msg 8111, Level 16, State 1, Line 1
-- Cannot define PRIMARY KEY constraint on nullable column in table 'T_test'.
-- Server: Msg 1750, Level 16, State 1, Line 1
-- Could not create constraint. See previous errors.
Johan
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