## Adding a Number of Days to a Date in T-SQL

Have you ever wanted to add or subtract a certain number of days from a date in SQL Server? Whether you need to calculate the arrival date of a package or adjust the departure date of a flight, T-SQL provides a simple solution.

In this article, we’ll explore how to add a specific number of days to a date using T-SQL’s powerful DATEADD() function.

## Using the DATEADD() Function

First, let’s review what the DATEADD() function is and what it does. In T-SQL, DATEADD() is a built-in function that adds a specified time interval to a given date.

The syntax of the DATEADD() function is as follows:

`DATEADD(interval, number, date)`

Here, interval refers to the unit of time you want to add or subtract (e.g., day, month, year), number specifies how many units you want to add or subtract, and date is the starting date to which you want to apply the interval. For example, suppose you wanted to add 7 days to the current date.

You could accomplish this with the following T-SQL statement:

`SELECT DATEADD(day, 7, GETDATE())`

In this case, the interval is “day” since we’re adding days, the number is 7, and the starting date is the current date (which we obtain using the GETDATE() function). The result of this statement would be a date 7 days into the future from the current date.

## Arguments for DATEADD()

Let’s examine each of the arguments for the DATEADD() function in more detail.

### Unit of Time

The first argument of DATEADD() specifies the unit of time you want to add or subtract. The following table lists the supported values for this argument:

Interval | Abbreviation |
---|---|

year | yy, yyyy |

quarter | qq, q |

month | mm, m |

dayofyear | dy, y |

day | dd, d |

week | wk, ww |

hour | hh |

minute | mi, n |

second | ss, s |

millisecond | ms |

microsecond | mcs |

nanosecond | ns |

### How Many

The second argument of DATEADD() specifies how many units of time you want to add or subtract. This argument can be a positive or negative integer.

If you want to add units of time, you should use a positive number. If you want to subtract units of time, you should use a negative number.

### Column

The third argument of DATEADD() specifies the starting date to which you want to apply the interval. This argument can be a column that stores date values or any expression that returns a date value (e.g., a variable that holds a date value).

In most cases, you’ll use GETDATE() to get the current date and time or a column from a table.

## Example with Flight Departure Dates

Now that you understand how the DATEADD() function works, let’s look at a practical example of how to use it to adjust the departure dates for flights. Suppose you have a table called Flights that contains flight information, including the departure date.

Here’s what the table might look like:

Code | DepartureDate |
---|---|

101 | 2022-01-01 |

102 | 2022-01-03 |

103 | 2022-01-05 |

## Changing Departure Dates for Flights

Suppose you want to update the departure date for all flights so that they depart 3 days later than originally scheduled. You can accomplish this with the following T-SQL statement:

```
UPDATE Flights
SET DepartureDate = DATEADD(day, 3, DepartureDate)
```

In this case, we’re updating the Flights table by adding 3 days to the DepartureDate column. The result is that all flights will depart 3 days later than originally scheduled.

## Using DATEADD() Function for all Flights

To see the new departure dates for all flights, you can simply query the Flights table:

```
SELECT Code, DepartureDate AS ChangedDepartureDate
FROM Flights
```

This will return a table that shows the flight codes and the updated departure dates:

Code | ChangedDepartureDate |
---|---|

101 | 2022-01-04 |

102 | 2022-01-06 |

103 | 2022-01-08 |

## Conclusion

In conclusion, the DATEADD() function in T-SQL provides a simple and efficient way to add or subtract a specified number of days from a date. By understanding the different arguments for the function, you can easily adjust dates for a variety of practical scenarios, such as changing flight schedules or calculating due dates for projects.

With this knowledge, you can handle date manipulation in T-SQL with confidence and ease.

## 3) Discussion on DATEADD() Function

The DATEADD() function in T-SQL is a useful tool for adding or subtracting a defined number of units of time from a given date. This function is extremely flexible and can be used for manipulating dates, times, and datetime values.

### Functionality of DATEADD()

The DATEADD() function enables you to add or subtract a specified number of units of time to or from date values in SQL Server. This function can be used with different units of time such as days, months, years, hours, minutes, seconds, milliseconds, and so on.

The result of using DATEADD() is always a new date, time, or datetime value, depending on the inputs provided. DATEADD() can be extremely useful when working with data that has dates or times as a vital component.

For instance, it could be used to adjust due dates for payments or project timelines. Additionally, some applications in finance like calculating interests and maturities rely on date manipulation.

The function can also be used to build a calendar or a booking system application.

### Arguments for DATEADD() Explained

The syntax of the DATEADD() function uses three arguments. The first argument is the interval, which represents the unit of time to be added.

The second argument is the number of units of time to be added. The third argument is an expression that returns a date or time value or a column that stores date or time values.

When specifying the interval argument of DATEADD(), you can use a variety of abbreviations that correspond to different units of time. For instance, to add a number of days, you would use the keyword ‘day’ or its abbreviation ‘d’.

Other abbreviations can be used for months, years, hours, minutes, seconds, and so forth. It is crucial to ensure that the interval abbreviation is appropriately used in the query.

The second argument of DATEADD() specifies the number of time units that should be added to or subtracted from the original date or time value. This argument can be either a positive or negative integer value.

If it is positive, the date or time value will be advanced into the future, and if it is negative, the date or time value will be shifted into the past. The third and final argument of DATEADD() simply refers to the original date or time value that you are looking to add or subtract the designated amount of time to.

This will essentially be the starting point of your date manipulation operation. 5)

## Conclusion

In conclusion, the DATEADD() function is a versatile and valuable tool for date and time manipulation in SQL Server.

With the use of simple interval abbreviations, you can easily adjust dates and times to whatever specific needs you have. When using this function, it’s crucial to ensure that the input format and order of arguments are correct to avoid errors.

Overall, when you need to add or subtract a certain number of units of time to a given date, DATEADD() is an excellent solution. With its straightforward syntax, it is easy to understand, flexible, and provides a quick and reliable way to perform date manipulation.

By mastering this function, you can accomplish a range of tasks in SQL Server with ease and efficiency. In conclusion, the DATEADD() function in T-SQL is an essential tool for date and time manipulation.

By using this function, you can conveniently add or subtract a specific number of units of time to a given date. To use this function effectively, it is essential to understand the three arguments of the function, which include interval, number, and expression.

When used appropriately, DATEADD() provides a simple and efficient solution to date manipulation, making it an essential tool for anyone working with SQL Server. Overall, by mastering this function and understanding its usage, you can quickly and efficiently perform date manipulation tasks and achieve your goals with ease.