SQL is a programming language that is used to communicate with databases and to manage the data stored in them. One of the most important aspects of SQL is working with dates and times. In many cases, you may need to query data that is based on a specific date or time range. However, there are also times when you need to work with the date or time itself, such as when you want to subtract a day from the current date. In this article, we will explore how to work with dates in SQL, specifically using the GETDATE function and how to subtract a day from that date without including the time using code examples.
The GETDATE Function
The GETDATE function is a built-in function in SQL that returns the current date and time. The syntax of the GETDATE function is as follows:
GETDATE()
This function will return a datetime value, which is a combination of both a date and a time. Here is an example of how you can use the GETDATE function to retrieve the current date and time:
SELECT GETDATE();
This statement will return the current date and time in the following format:
2022-05-19 16:28:36.240
Subtracting a Day from the Current Date
Now that we know how to retrieve the current date and time using the GETDATE function, let's take a look at how we can subtract a day from that date without including the time. One method is to use the DATEADD function in SQL. The DATEADD function allows you to add or subtract a specified time interval from a given date. To subtract a day from the current date, we can use the following code:
SELECT DATEADD(DAY, -1, CAST(GETDATE() AS DATE))
In this example, we are using the DATEADD function to subtract one day from the current date. We are using the DAY argument to specify that we want to subtract a day. The -1 argument specifies that we want to subtract one day. Finally, we are using the CAST function to cast the result as a date only value, which removes the time component from the value. Here is the result:
2022-05-18
Notice that the time component has been stripped from the result, giving us only the date value of one day ago.
Another method to achieve the same result is to use the CONVERT function. You can use the CONVERT function to convert the datetime value returned by the GETDATE function into a date value only, then subtract one day from that. Here is an example of how to do that:
SELECT CONVERT(DATE, DATEADD(DAY, -1, GETDATE()))
This statement first uses the DATEADD function to subtract one day from the current date and time, then converts the result into a date value only using the CONVERT function. Here is the result:
2022-05-18
Again, the time component has been removed, giving us only the date value of one day ago.
Conclusion
In this article, we have explored how to work with dates and times in SQL. Specifically, we looked at how to retrieve the current date and time using the GETDATE function, and how to subtract a day from the current date without including the time. We covered two methods for achieving this, using the DATEADD and CONVERT functions. While there are many other date and time functions available in SQL, mastering these fundamentals is essential for working with databases effectively.
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GETDATE Function
The GETDATE function is a commonly used function in SQL that returns the current date and time according to the system on which the SQL Server is running. It is a non-deterministic function and is evaluated every time it is referenced in a query. It is often used in queries to limit results based on the current date and time or to populate timestamp columns.
For example, suppose you want to retrieve all the records that have a timestamp of today, you can use the GETDATE function in the WHERE clause of your query as follows:
SELECT *
FROM myTable
WHERE CAST(myTimestamp AS DATE) = CAST(GETDATE() AS DATE)
This statement retrieves all the records from the myTable table where the date component of myTimestamp column is equal to the current date.
DATEADD Function
The DATEADD function is used to add or subtract a specified amount of time to a given date. It takes three arguments: the date part to be added or subtracted, the amount of time to be added or subtracted, and the initial date to which the change will be applied.
The first argument is a string that specifies which datepart to add or subtract. It can be any of the following:
- 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)
The second argument is an integer that specifies the amount of time to add or subtract. The third argument is the initial value to which the change will be applied. For example, to add 10 days to the current date, you can use the following expression:
SELECT DATEADD(day, 10, GETDATE())
This statement returns a datetime value that is 10 days into the future from the current date and time.
CAST and CONVERT Functions
The CAST and CONVERT functions are used to convert one data type to another. The CAST function is used to convert an expression of one data type to another data type, while the CONVERT function is used to convert an expression from one data type to another data type using a specific style.
To convert a datetime value to a date-only value, you can use the CAST function as follows:
SELECT CAST(GETDATE() AS DATE)
This statement returns the date component of the current date and time.
Alternatively, you can use the CONVERT function as follows:
SELECT CONVERT(DATE, GETDATE())
This statement also returns the date component of the current date and time.
Conclusion
Working with dates and times is an essential part of SQL. In this article, we explored the fundamentals of working with dates, including the GETDATE, DATEADD, CAST, and CONVERT functions. By mastering these functions, you can efficiently query your databases and manipulate dates and times to meet your specific requirements.
Popular questions
Sure, here are 5 questions and answers related to the topic of 'SQL GETDATE minus 1 day without time with code examples':
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What is the purpose of the GETDATE function in SQL?
Answer: The GETDATE function is used to return the current date and time according to the system on which the SQL Server is running. This function is commonly used in queries to limit results based on the current date and time or to populate timestamp columns. -
What is the difference between the DATEADD and CONVERT functions in SQL?
Answer: The DATEADD function is used to add or subtract a specified amount of time to a given date, while the CONVERT function is used to convert an expression from one data type to another data type using a specific style. Both functions can be used to subtract a day from the current date and time, but they have different syntax. -
How can you subtract a day from the current date without including the time component in SQL?
Answer: To subtract a day from the current date without including the time component, you can use either the DATEADD or CONVERT function along with the GETDATE function. Here is an example of using the DATEADD function: SELECT DATEADD(DAY, -1, CAST(GETDATE() AS DATE)). This statement subtracts one day from the current date and time, and then casts the result as a date value only, ignoring the time component. -
Can you use the GETDATE function in a query to limit results based on a specific date range?
Answer: Yes, the GETDATE function can be used in queries to limit results based on a specific date range. For example, to retrieve all the records that have a timestamp of today, you can use the GETDATE function in the WHERE clause of your query, like this: SELECT * FROM myTable WHERE CAST(myTimestamp AS DATE) = CAST(GETDATE() AS DATE) -
What are some other date and time functions available in SQL?
Answer: There are many date and time functions available in SQL, including DATEDIFF, DATEPART, DATENAME, DATEFROMPARTS, and EOMONTH, among others. These functions can be used to calculate the difference between two dates, extract specific parts of a date, construct a date from its components, and find the last day of a month, respectively.
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