Example: INSERT and GENERATED BY DEFAULT Identity Columns
The result of inserting values into the same table defined in “Example: INSERT and GENERATED ALWAYS Identity Columns” on page 380 shows the difference in the behavior of the two identity column types. Because GENERATED BY DEFAULT only generates values when an INSERT request does not supply them, the same insert operations produce different results.
Assume that column_1 of newly created table_1 is an identity column defined as GENERATED BY DEFAULT. The following INSERT requests generate numbers for column_1 of the inserted rows only if they do not specify a value for that column.
INSERT INTO table_1 (column_1, column_2, column_3)
VALUES (111,111,111);
INSERT INTO table_1 (column_1, column_2, column_2)
VALUES (,222,222);
Check the result of the insert operations by selecting all the rows from table_1.
SELECT *
FROM table_1;
*** Query completed. 2 rows found. 3 columns returned.
*** Total elapsed time was 1 second.
column_1 column_2 column_3
--------- --------- ---------
111 111 111
1 222 222