How to convert MM/YY to YYYY-MM-DD with a specific day in MySQL?

To convert, use STR_TO_DATE(), as in the below syntax. Concatenate the day value with CONCAT() −

select str_to_date(concat('yourDateValue/', yourColumnName), '%d/%m/%y') as anyAliasName
from yourTableName;

Let us create a table −

mysql> create table demo46
−> (
−> id int not null auto_increment primary key,
−> short_date varchar(20)
−> );
Query OK, 0 rows affected (0.60 sec)

Insert some records into the table with the help of insert command −

mysql> insert into demo46(short_date) values('09/18');
Query OK, 1 row affected (0.08 sec)

mysql> insert into demo46(short_date) values('12/20');
Query OK, 1 row affected (0.12 sec)

mysql> insert into demo46(short_date) values('11/20');
Query OK, 1 row affected (0.20 sec)

Display records from the table using select statement −

mysql> select *from demo46;

This will produce the following output −

+----+------------+
| id | short_date |
+----+------------+
|  1 | 09/18      |
|  2 | 12/20      |
|  3 | 11/20      |
+----+------------+
3 rows in set (0.00 sec)

Following is the query to convert MM/YY to YYYY-MM-DD in MySQL.

mysql> select str_to_date(concat('24/', short_date), '%d/%m/%y') as Convert_In_Full_Date
−> from demo46;

This will produce the following output −

+----------------------+
| Convert_In_Full_Date |
+----------------------+
| 2018−09−24           |
| 2020−12−24           |
| 2020−11−24           |
+----------------------+
3 rows in set (0.00 sec)