How to add some days to str_to_date() MySQL function?

You can use DATE_ADD() function from MySQL. Let us first create a table −

mysql> create table DemoTable
   -> (
   -> ShippingDate varchar(100)
   -> );
Query OK, 0 rows affected (0.67 sec)

Insert some records in the table using insert command −

mysql> insert into DemoTable values('06-01-2019');
Query OK, 1 row affected (0.15 sec)

mysql> insert into DemoTable values('01-04-2017');
Query OK, 1 row affected (0.19 sec)

mysql> insert into DemoTable values('29-06-2019');
Query OK, 1 row affected (0.47 sec)

Display all records from the table using select statement −

mysql> select *from DemoTable;

Output

+--------------+
| ShippingDate |
+--------------+
| 06-01-2019   |
| 01-04-2017   |
| 29-06-2019   |
+--------------+
3 rows in set (0.00 sec)

Following is the query to add some days to str_to_date() MySQL function. Here, we have added 6 days −

mysql> select date_add(str_to_date(ShippingDate,'%d-%m-%Y'),interval 6 day) as newShippingDate from DemoTable;

Output

+-----------------+
| newShippingDate |
+-----------------+
| 2019-01-12      |
| 2017-04-07      |
| 2019-07-05      |
+-----------------+
3 rows in set (0.00 sec)