The import utility can be used to import data into a table containing (nonidentity) generated columns whether or not the input data has generated column values.
If no generated column-related file type modifiers are used, the import utility works according to the following rules:
There are two ways you can simplify the import of data into tables that contain a generated column: the generatedmissing and the generatedignore file type modifiers.
create table table1 (c1 int,
c2 int,
g1 int generated always as (c1 + c2),
g2 int generated always as (2 * c1),
c3 char(1))
A user might want to
import data from a file (load.del) into TABLE1,
and this data might have been exported from a table that does not
have any generated columns. The following is an example of such a
file: 1, 5, J
2, 6, K
3, 7, I
One way to import this file would be to explicitly
list the columns to be imported through the IMPORT command
as follows: db2 import from import.del of del replace into table1 (c1, c2, c3)
For
a table with many columns, however, this syntax might be cumbersome
and prone to error. An alternate method of importing the file is to
use the generatedmissing file type modifier as follows:
db2 import from import.del of del modified by generatedmissing
replace into table1
1, 5, 10, 15, J
2, 6, 11, 16, K
3, 7, 12, 17, I
The user-supplied, non-NULL values of 10, 11,
and 12 (for g1), and 15, 16,
and 17 (for g2) result in the row being rejected
(SQL3550W). To avoid this, the user could issue the
following IMPORT command: db2 import from import.del of del method P(1, 2, 5)
replace into table1 (c1, c2, c3)
Again, this approach
might be cumbersome and prone to error if the table has many columns.
The generatedignore modifier simplifies the syntax
as follows: db2 import from import.del of del modified by generatedignore
replace into table1
For an INSERT_UPDATE, if the generated column is also a primary key and the generatedignore modifier is specified, the IMPORT command honors the generatedignore modifier. The IMPORT command does not substitute the user-supplied value for this column in the WHERE clause of the UPDATE statement.