Hi,
I'm new to DB2, but am relatively familiar with databases, and I've run
into something I don't fully understand. I created a table tab4, then,
after the fact, altered the table so that one of the columns must not
contain null values. I used the command:
db2inst1@reihe5 1:~> db2 "alter table tab4 ADD CHECK (sp1 is NOT NULL)"
// using "alter table add constraint" didn't work
I then created a table tab5, defining the column as NOT NULL at
creation time.
db2inst1@reihe5 1:~> db2 "create table tab5 (sp1 int NOT NULL)"
Running "describe table" against each of the two, I get an unexpected
result:
db2inst1@reihe5 1:~> db2 "describe table tab4"
Column Type Type
name schema name Length
Scale Nulls
------------------------------ --------- ------------------ --------
----- ------
SP1 SYSIBM INTEGER 4
0 Yes
SP2 SYSIBM CHARACTER 10
0 Yes
2 record(s) selected.
db2inst1@reihe5 1:~> db2 "describe table tab5"
Column Type Type
name schema name Length
Scale Nulls
------------------------------ --------- ------------------ --------
----- ------
SP1 SYSIBM INTEGER 4
0 No
1 record(s) selected.
// expected behavior since I defined sp1 as NOT NULL at create time
Since I added the check constraint to tab4, why does the "Nulls" column
still show "Yes"? Is there a way to change that other than dropping the
table and recreating it?
Thanks,
Mike
2  4357  mi*********@gma il.com wrote: Since I added the check constraint to tab4, why does the "Nulls" column
still show "Yes"? Is there a way to change that other than dropping the
table and recreating it?
DB2 treats NOT NULL as column property.
CHECK (c1 IS NOT NOT) on the other hand is a check constraint like any
other.
Describe only tests for the column preperty.
Currently in DB2 for LUW you would have to drop and recreate the table
to alter the NOT NULL column property.
DB2 V8.2 has an ALTE TABEL "wizard" built into control center which
automates that process.
Cheers
Serge
--
Serge Rielau
DB2 SQL Compiler Development
IBM Toronto Lab
Serge,
Thanks for responding. I had a suspicion that it might have been
something along those lines, but you locked it in for me.
Mike
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