primary key ??

[dba_usa]

hi friends,
after creating a table with no constraints and then loading data into it, can we then define a primary key to that table ?

thanks

[marist89]

Sure,
ALTER TABLE xyz ADD CONSTRAINT pk_xyz PRIMARY KEY (pk_field);

[Shestakov]

Better :

ALTER TABLE xyz ADD CONSTRAINT pk_xyz PRIMARY KEY (pk_field)
using index
tablespace ...
pctfree XX
storage (...)
exception into .....;

because you loaded data into table and nobody never sure that PK column is primary key.

[dba_usa]

thanks , the primary key worked, but, after creating a table and if i have to make a column not null, which already has data in it what do i do?

[jmodic]

Simply alter the table.

ALTER TABLE my_table MODIFY (my_column NOT NULL);

If there is any NULL value in MY_COLUMN the above will fail. You will first need to set all rows to have non-null value in that column, then you add NOT NULL constraint.