This function is used to calculate the number of days in which start_date is increased by days.

To obtain the date with a specified change range based on the current date, use this function together with the current_date or getdate function.

Note that the logic of this function is opposite to that of the date_sub function.

date_add(string startdate, int days)

**Table 1** Parameters
Parameter	Mandatory	Type	Description
start_date	Yes	DATE or STRING	Start date The following formats are supported: yyyy-mm-dd yyyy-mm-dd hh:mi:ss yyyy-mm-dd hh:mi:ss.ff3
days	Yes	BIGINT	Number of days to be added If the value is greater than 0, the number of days is increased. If the value is less than 0, the number of days is subtracted. If the value is 0, the date does not change. If the value is NULL, NULL is returned.

The return value is of the DATE type, in the yyyy-mm-dd format.

If the value of start_date is not of the DATE or STRING type, the error message "data type mismatch" is displayed.
If the value of start_date is of the DATE or STRING type but is not in one of the supported formats, NULL is returned.
If the value of start_date is NULL, NULL is returned.
If the value of days is NULL, NULL is returned.

The value 2023-03-01 is returned after one day is added.

select date_add('2023-02-28 00:00:00', 1);

The value 2023-02-27 is returned after one day is subtracted.

select date_add(date '2023-02-28', -1);

The value 2023-03-20 is returned.

select date_add('2023-02-28 00:00:00', 20);

If the current time is 2023-08-14 16:00:00, 2023-08-13 is returned.

select date_add(getdate(),-1);

The value NULL is returned.

select date_add('2023-02-28 00:00:00', null);