MySQL query to add days with interval of 45 days and display the output in a new column

For this, you can use date_add(). Let us first create a table −

mysql> create table DemoTable1930
   (
   DueTime datetime
   );
Query OK, 0 rows affected (0.00 sec)

Insert some records in the table using insert command −

mysql> insert into DemoTable1930 values('2017-10-21');
Query OK, 1 row affected (0.00 sec)
mysql> insert into DemoTable1930 values('2019-12-14');
Query OK, 1 row affected (0.00 sec)
mysql> insert into DemoTable1930 values('2018-11-26');
Query OK, 1 row affected (0.00 sec)
mysql> insert into DemoTable1930 values('2014-06-16');
Query OK, 1 row affected (0.00 sec)

Display all records from the table using select statement −

mysql> select * from DemoTable1930;

This will produce the following output −

+---------------------+
| DueTime             |
+---------------------+
| 2017-10-21 00:00:00 |
| 2019-12-14 00:00:00 |
| 2018-11-26 00:00:00 |
| 2014-06-16 00:00:00 |
+---------------------+
4 rows in set (0.00 sec)

Here is the query to add days −

mysql> select DueTime,date_add(DueTime, interval 45 day) as ManyDays from DemoTable1930;

This will produce the following output −

+---------------------+---------------------+
| DueTime             | ManyDays            |
+---------------------+---------------------+
| 2017-10-21 00:00:00 | 2017-12-05 00:00:00 |
| 2019-12-14 00:00:00 | 2020-01-28 00:00:00 |
| 2018-11-26 00:00:00 | 2019-01-10 00:00:00 |
| 2014-06-16 00:00:00 | 2014-07-31 00:00:00 |
+---------------------+---------------------+
4 rows in set (0.00 sec)