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Can a primary key have null values? If we try to insert a
null value in a primary key column, will it work or give an
error code?

Question Posted / ratheesh nellikal

Answer Posted / ratheesh nellikal

In DB2 you can not create a primary key on a column which
is not 'not null'.
If you are trying to create a primary key on a column which
is not 'not null' then dbb2 will return an error like this

SQL0542N "feild_name" cannot be a column of a primary key
or unique key because it can contain null values.
SQLSTATE=42831

But once u alter the table and set the column to 'NOT NULL'
then you can make it as primary key.

Now if u r trying to insert an null value to ur primary key
column then db2 will trows an error like

SQL0407N Assignment of a NULL value to a NOT NULL
column "TBSPACEID=5, TABLEID=404, COLNO=0" is not allowed.
SQLSTATE=23502.

In short you can not make a column which can hold 'NULL'
value as your primary key and you can not insert a 'NULL'
value into your primary key feild.

Cheers,
Ratheesh Nellikal

Is This Answer Correct ?    7 Yes 1 No



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