Oracle 21c

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CREATE TABLE table_name (col1, col2, col3) AS
SELECT LEVEL, LEVEL, LEVEL FROM DUAL CONNECT BY LEVEL <= 3;
3 rows affected

SELECT * FROM table_name;


COL1
COL2
COL3


1
1
1

2
2
2

3
3
3


INSERT INTO table_name (col1, col2, col3)
SELECT col1, col2, col3 + 1
FROM   table_name
3 rows affected

SELECT * FROM table_name;


COL1
COL2
COL3


1
1
1

2
2
2

3
3
3

1
1
2

2
2
3

3
3
4


INSERT INTO table_name (col1, col2, col3)
SELECT col1, col2, col3 + COUNT(*) OVER ()
FROM   table_name
6 rows affected

SELECT * FROM table_name;


COL1
COL2
COL3


1
1
1

2
2
2

3
3
3

1
1
2

2
2
3

3
3
4

1
1
7

2
2
8

3
3
9

1
1
8

2
2
9

3
3
10


DROP TABLE table_name;
CREATE SEQUENCE table_name__col3__seq;
CREATE TABLE table_name (col1, col2, col3) AS
SELECT LEVEL, LEVEL, table_name__col3__seq.NEXTVAL FROM DUAL CONNECT BY LEVEL <= 3;
3 rows affected

SELECT * FROM table_name;


COL1
COL2
COL3


1
1
1

2
2
2

3
3
3


INSERT INTO table_name (col1, col2, col3)
SELECT col1, col2, table_name__col3__seq.NEXTVAL
FROM   table_name
3 rows affected

SELECT * FROM table_name;


COL1
COL2
COL3


1
1
1

2
2
2

3
3
3

1
1
4

2
2
5

3
3
6