constraint c_dept_name  unique (deptname)
) in mb_data1"

--添加主键成功
db2inst1@sles11:~/sqllib> db2 "alter table d add constraint p_d_dept  primary key (dept)"

--删除表
db2inst1@sles11:~/sqllib> db2 drop table d                                              

--创建表d，列dept 允许为 null
db2inst1@sles11:~/sqllib> db2 "create table d (                                         
dept char(3) ,
deptname char(20) not null,
constraint c_dept_name  unique (deptname)
) in mb_data1"
DB20000I  The SQL command completed successfully.

--设置主键报错
db2inst1@sles11:~/sqllib> db2 "alter table d add constraint p_d_dept  primary key (dept)"
DB21034E  The command was processed as an SQL statement because it was not a
valid Command Line Processor command.  During SQL processing it returned:
SQL0542N  The column named "DEPT" cannot be a column of a primary key or
unique key constraint because it can contain null values.  SQLSTATE=42831

--添加not null 约束
db2inst1@sles11:~/sqllib> db2 "alter table d alter column dept set not null"            
DB20000I  The SQL command completed successfully.

--无法添加主键 为什么呢？
db2inst1@sles11:~/sqllib> db2 "alter table d add constraint p_d_dept  primary key (dept)"
DB21034E  The command was processed as an SQL statement because it was not a
valid Command Line Processor command.  During SQL processing it returned:
SQL0668N  Operation not allowed for reason code "7" on table "DB2INST1.D". 
SQLSTATE=57016

-----------------------------------------------------------------------------------------
--解决方案：重组表
db2 reorg table db2inst1.d