Date Time Functions in SQL and the Use of Date Time Functions

Date Time functions in SQL

There are various Date time functions available in SQL which allow us to create trigger based on it. Date time function allow us to check whether an input string is a date or not. Also, we can check what’s the day or week number on a specific date using date time function.

Date Time

Let’s check various date time function available with us:

  1. IsDate

The isDate function is used to check whether the input string is a date or not.

Command: Select isDate(“2012-05-30”), it will return 1

If the input string is not a date, the IsDate date time function will return zero.

The isDate function works well on date, time and datetime datatype but not with datetime2 (timestamp with nanoseconds)

2. Day()

This date time function returns the “day number” of the specified input date string.

Command: Select Day(“2012-02-30 02:35:35”) – Returns 30

3. Month()

This sql date time function returns the “month number” of the specified input date string.

Command: Select Month(“2012-02-30 02:35:35”) – Returns 2

4. Day()

This sql date time function returns the “day number” of the specified input date string.

Command: Select Day(“2012-02-30 02:35:35”) – Returns 30

5. DateName()

The DateName() date time function returns a string value while other date time functions return integer value.

There are various attributes that can be used with the DateName() function. let’s me share some examples of it here:

  1. DateTime(Day, “Date value”|”DateTime Value”) – This function returns the day value (exception it is integer)

Command: Select DateTime(Day, “2013-05-23”) – the output will be 2

2. DateTime(WeekDay, “Date value”|”DateTime Value” – This function returns the week day value

Command: Select DateTime(WeekDay, “2013-05-23”) – the output will be Saturday.

3. DateTime(Month, “Date value”|”DateTime Value”)  – It returns the month value as a string

Command: Select DateTime(Month, “2013-05-23”) – the output will be May.

6. Datepart()

The DatePart() function works similar way as DateName function to find out the weekDay. the only difference between DatePart() and DateName() function is Datepart() returns an integer.

e.g. Select DatePart(WeekDay, “2013-05-25”) will return 2 if it is Tuesday

7. DateAdd()

This sql function will add day, month or year according to the specified value.

Command: Select DateAdd(Day|Month|Year, integer value of addition, Date Value)

e.g. Select DateAdd(Day, 10, “2013-05-20”) – This will output “2013-05-30”

Date Diff

8. DateDiff()

This sql function will add day, month or year according to the specified value.

Command: Select DateDiff(Day|Month|Year, Date value 1,Date value 2)

e.g. Select DateAdd(Month, “2013-05-20″,”2013-01-20”) – This will output 4

Cast and Convert Functions in SQL

Cast and convert functions allow you to convert one data type into another.

Syntax of Cast function:

Select cast(Column_name as Data type)

e.g. Select cast(date as nvarchar)

Syntax of Convert function:

Convert function lets you choose style parameter for string values only. The style feature is not available in cast function. By styling I mean a user defined format in which the output is required.

e.g. Select convert(data type, column_name, style)

There are some specific style codes like 103 means : dd/mm/yyyy. Thus the following example:

Select convert(nvarchar, DateOfBirth, 103)