DATEADD

DATEADD is a date and time arithmetic function primarily associated with SQL Server's Transact-SQL. It returns a new date/time value obtained by adding a specified interval to a given date/time input. The function is widely used in queries, stored procedures, and ETL processes to shift dates forward or backward by a given amount.

Syntax: DATEADD(datepart, number, date). datepart is the component to be added (for example year, quarter, month, day, hour, minute, second, millisecond; many implementations also accept common abbreviations such as yy for year or dd for day). number is an integer. Positive values move forward in time; negative values move backward. date is the base date/time value, which can be a date, datetime, datetime2, smalldatetime, or similar types depending on the database.

Return type: The function returns a value of the same data type as the input date.

Examples: DATEADD(day, 7, '2023-01-01') yields 2023-01-08. DATEADD(month, -1, '2023-05-15') yields 2023-04-15.

Notes: When the resulting date is invalid for the target date part (for example, adding months to a day that does not exist in the resulting month), behavior is defined by the database system and may adjust to the last valid day or raise an error. Time zone and offset considerations may apply if the input includes such components.

Portability: DATEADD is specific to SQL Server; other databases provide similar functionality under different names or via arithmetic with intervals (for example, DATE_ADD in MySQL, or adding an INTERVAL in PostgreSQL and Oracle). Always consult the respective documentation for precise syntax and behavior.