Create date from day, month, year fields in MySQL?

You can use in-built function STR_TO_DATE() from MySQL. The syntax is as follows −

SELECT
STR_TO_DATE(CONCAT(yourYearColumName,'-',LPAD(yourMonthColumName,2,'00'),'-',LPAD(yourDayColumName,2,'00')), '%Y-%m-%d') as anyVariableName from yourTableName;

To understand the above syntax, let us create a table. The query to create a table is as follows −

mysql> create table DateCreateDemo
   −> (
   −> `Day` varchar(2),
   −> `Month` varchar(2),
   −> `Year` varchar(4)
   −> );
Query OK, 0 rows affected (1.68 sec)

Insert values for all fields using insert command. The query is as follows −

mysql> insert into DateCreateDemo values('15','12','2018');
Query OK, 1 row affected (0.09 sec)

mysql> insert into DateCreateDemo values('10','11','2016');
Query OK, 1 row affected (0.37 sec)

mysql> insert into DateCreateDemo values('12','6','2017');
Query OK, 1 row affected (0.12 sec)

mysql> insert into DateCreateDemo values('9','8','2019');
Query OK, 1 row affected (0.17 sec)

mysql> insert into DateCreateDemo values('10','5','2020');
Query OK, 1 row affected (0.09 sec)

Display all records from the table using select statement. The query is as follows −

mysql> select *from DateCreateDemo;

The following is the output −

+------+-------+------+
| Day  | Month | Year |
+------+-------+------+
| 15   | 12    | 2018 |
| 10   | 11    | 2016 |
| 12   | 6     | 2017 |
| 9    | 8     | 2019 |
| 10   | 5     | 2020 |
+------+-------+------+
5 rows in set (0.00 sec)

Create a date using the above three fields which is ‘Day’,’Month’ and ‘Year’. The query is as follows −

mysql> select
   −> STR_TO_DATE(CONCAT(Year,'-',LPAD(Month,2,'00'),'-',LPAD(day,2,'00')), '%Y-%m-%d') as DateDemo from DateCreateDemo;

The following is the output −

+------------+
| DateDemo   |
+------------+
| 2018-12-15 |
| 2016-11-10 |
| 2017-06-12 |
| 2019-08-09 |
| 2020-05-10 |
+------------+
5 rows in set (0.06 sec)