Assume that column_1 of newly created table_1 is an identity column defined as GENERATED ALWAYS. The following INSERT statements automatically generate numbers for column_1 of the inserted rows, even if they 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 inserts 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 --------- --------- --------- 2 111 111 1 222 222
- Even though the value 111 was specified for column_1 in the first insert, the value is rejected and replaced by the generated value 2 because column_1 is defined as GENERATED ALWAYS.
- A warning is returned to the requestor when a user-specified value is overridden by a system-generated number.
- The first number in the identity column sequence is not necessarily allocated to the first row inserted because of parallelism.