Greetings, Dev! In this article, we will be discussing the date part in SQL Server. Date and time are an integral part of any database management system, and SQL Server is no exception. Understanding the date part in SQL Server is critical for efficiently manipulating, querying, and managing date and time data. We will start by introducing the concept of the date part and move on to the different functions and operators available in SQL Server.
Introduction to Date Part
Before we dive into the different functions and operators, let us first understand what the date part is. The date part is a component of the date and time data that refers to a specific portion of the date or time value. For example, in the date ‘2022-02-01′, the year is the date part. Similarly, in the time ’17:25:30’, the minute is the date part.
Manipulating the date parts is essential when working with SQL Server as it allows us to extract specific information from a date or time value. This information can then be used to perform calculations, comparisons, and other operations.
What is the Date Part Function in SQL Server?
The date part function in SQL Server is used to extract a specific date part from a date or time value. The function returns an integer value that represents the specified date part. The syntax for the function is as follows:
Function |
Description |
|---|---|
DATEPART(datepart, date) |
Returns the specified date part of a date or time value. |
The datepart parameter is a string or an expression that specifies the date part to be returned. This parameter can be any of the following:
Date Part |
Description |
|---|---|
year |
Returns the year of the specified date value. |
quarter |
Returns the quarter of the year for the specified date value. |
month |
Returns the month of the year for the specified date value. |
dayofyear |
Returns the day of the year for the specified date value. |
day |
Returns the day of the month for the specified date value. |
week |
Returns the week of the year for the specified date value. |
weekday |
Returns the weekday number for the specified date value. |
hour |
Returns the hour of the day for the specified time value. |
minute |
Returns the minute of the hour for the specified time value. |
second |
Returns the second of the minute for the specified time value. |
millisecond |
Returns the millisecond of the second for the specified time value. |
The date parameter is a date or time value from which the specified date part is to be returned.
Examples of Date Part Function in SQL Server
Let us take a few examples to demonstrate the usage of the date part function in SQL Server:
Example 1: Extracting the Year
To extract the year from a date value, we can use the following syntax:
SELECT DATEPART(year, '2022-02-01')The query will return the following result:
| Result |
|---|
| 2022 |
Example 2: Extracting the Month
To extract the month from a date value, we can use the following syntax:
SELECT DATEPART(month, '2022-02-01')The query will return the following result:
| Result |
|---|
| 2 |
Example 3: Extracting the Hour
To extract the hour from a time value, we can use the following syntax:
SELECT DATEPART(hour, '17:25:30')The query will return the following result:
| Result |
|---|
| 17 |
Operators for Date Part in SQL Server
In addition to the date part function, SQL Server provides several operators that can be used to perform operations on date and time values. These operators allow us to add, subtract, and compare date and time values based on specific date parts.
Arithmetic Operators
The arithmetic operators available for date and time values are:
Operator |
Description |
|---|---|
+ |
Adds two date or time values together. |
– |
Subtracts one date or time value from another. |
When using the arithmetic operators with date and time values, it is necessary to enclose them in brackets to ensure the correct precedence of operators. For example:
SELECT DATEADD(month, 1, '2022-02-01') - '2022-01-01'The query will return the number of days between February 1, 2022, and January 1, 2022.
Comparison Operators
The comparison operators available for date and time values are:
Operator |
Description |
|---|---|
> |
Returns true if the left operand is greater than the right operand. |
>= |
Returns true if the left operand is greater than or equal to the right operand. |
< |
Returns true if the left operand is less than the right operand. |
<= |
Returns true if the left operand is less than or equal to the right operand. |
= |
Returns true if the left operand is equal to the right operand. |
<> |
Returns true if the left operand is not equal to the right operand. |
The comparison operators can be used to compare date and time values based on specific date parts. For example, to compare two dates based on the year, we can use the following syntax:
SELECT * FROM orders WHERE DATEPART(year, order_date) = 2022This will return all the orders that were placed in the year 2022.
FAQ
What is the difference between GETDATE() and SYSDATETIME() functions?
The GETDATE() function returns the current date and time value in the format of ‘yyyy-mm-dd hh:mm:ss’. The SYSDATETIME() function, on the other hand, returns the current date and time value in the format of ‘yyyy-mm-dd hh:mm:ss.mmmmmm’. The SYSDATETIME() function provides greater precision as it includes microseconds in the value.
Can the DATEPART() function be used with datetimeoffset data type?
Yes, the DATEPART() function can be used with the datetimeoffset data type. However, the function will return the specified date part in the UTC (Coordinated Universal Time) time zone. To retrieve the date part in a specific time zone, it is necessary to use the AT TIME ZONE clause.
What is the difference between DATEDIFF() and DATEADD() functions?
The DATEDIFF() function returns the difference between two date or time values in the specified date part. The DATEADD() function, on the other hand, adds a specified time interval to a date or time value. Both functions are useful in different scenarios based on the desired outcome.
Can the DATEPART() function be used with varchar data type?
No, the DATEPART() function cannot be used with the varchar data type. The date part function only works with the date and time data types in SQL Server.
What is the difference between YEAR() and DATEPART(year, date) function?
The YEAR() function is a T-SQL built-in function that returns the year of a specified date or time value. The DATEPART(year, date) function, on the other hand, is a date part function that can be used to extract the year from a date or time value. Both functions are similar in that they return the year of a date or time value, but the DATEPART() function provides greater flexibility as it can be used to extract other date parts as well.
Conclusion
In this article, we discussed the date part in SQL Server and the various functions and operators available for working with date and time data. We also demonstrated the usage of the DATEPART() function and the arithmetic and comparison operators. Remember, understanding the date part in SQL Server is essential for effectively managing date and time data in any database management system.