How to find out number of days in a month in MySQL?

To find the number of days in month, use the below syntax.

select DAY(LAST_DAY(yourColumnName)) as anyVariableName from yourTableName;

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

mysql> create table DaysInaGivenMonth
-> (
-> MonthName datetime
-> );
Query OK, 0 rows affected (1.62 sec)

Insert some records in the table using insert command. The query is as follows.

mysql> insert into DaysInaGivenMonth values(now());
Query OK, 1 row affected (0.24 sec)

mysql> insert into DaysInaGivenMonth values(date_add(now(),interval -1 month));
Query OK, 1 row affected (0.16 sec)

mysql> insert into DaysInaGivenMonth values(date_add(now(),interval -2 month));
Query OK, 1 row affected (0.10 sec)

mysql> insert into DaysInaGivenMonth values(date_add(now(),interval -3 month));
Query OK, 1 row affected (0.20 sec)

mysql> insert into DaysInaGivenMonth values(date_add(now(),interval -4 month));
Query OK, 1 row affected (0.23 sec)

mysql> insert into DaysInaGivenMonth values(date_add(now(),interval -5 month));
Query OK, 1 row affected (0.15 sec)

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

mysql> select *from DaysInaGivenMonth;

The following is the output.

+---------------------+
| MonthName           |
+---------------------+
| 2019-01-01 21:34:26 |
| 2018-12-01 21:34:55 |
| 2018-11-01 21:35:14 |
| 2018-10-01 21:35:20 |
| 2018-09-01 21:35:23 |
| 2018-08-01 21:35:27 |
+---------------------+
6 rows in set (0.00 sec)

Here is the query to find out the number of days in the months listed above.

mysql> select DAY(LAST_DAY(MonthName)) as DaysInMonth from DaysInaGivenMonth;

The following is the output.

+-------------+
| DaysInMonth |
+-------------+
| 31          |
| 31          |
| 30          |
| 31          |
| 30          |
| 31          |
+-------------+
6 rows in set (0.00 sec)