Hello Dev! Are you ready to learn about one of the most important functions in SQL Server? Look no further than the “convert” function, which allows you to change the data type of a value from one type to another. Whether you’re a seasoned SQL pro or just starting out, this guide will help you master the ins and outs of the convert function and how to use it to your advantage.
What is the Convert Function?
The convert function is a powerful tool in SQL Server that allows you to change the data type of a value from one type to another. This is particularly useful when dealing with data that has been input in the wrong format, or when using data that is stored in a different format than what is needed for a particular operation. Converting data types is an essential part of working with SQL Server, and using the convert function can help you do it quickly and efficiently.
How Does the Convert Function Work?
The convert function takes two arguments: the first is the target data type that you want to convert the value to, and the second is the value that you want to convert. For example, if you have a value that is stored as a string (VARCHAR) but you need it to be a number (INT), you can use the convert function to convert it:
Original Value |
Converted Value |
|---|---|
’42’ |
42 |
In this example, we used the convert function to change the data type of the value from a string to an integer, which is useful in many situations where data needs to be compared or used in calculations.
What Data Types Can Be Converted?
The convert function in SQL Server supports a wide range of data types, including:
- bigint
- bit
- datetime
- float
- int
- money
- nchar
- nvarchar
- real
- smallint
- tinyint
- uniqueidentifier
- varbinary
- varchar
As you can see, the convert function supports a wide range of data types, which makes it a versatile tool for many different situations.
Using the Convert Function in SQL Server
Converting Strings to Integers
One of the most common uses of the convert function is to convert string values to integer values. This is particularly useful when working with data that has been input in the wrong format, or when dealing with data that needs to be compared or used in calculations.
To convert a string value to an integer value using the convert function, you can use the following syntax:
SELECT CONVERT(INT, '42')In this example, we are converting the string value ’42’ to an integer value using the convert function. The result of this operation will be an integer value of 42, which can be used in any operation that requires an integer value.
Converting Integers to Strings
Another common use of the convert function is to convert integer values to string values. This is useful when working with data that needs to be output in a particular format, or when dealing with data that needs to be displayed in a user interface.
To convert an integer value to a string value using the convert function, you can use the following syntax:
SELECT CONVERT(VARCHAR, 42)In this example, we are converting the integer value 42 to a string value using the convert function. The result of this operation will be a string value of ’42’, which can be used in any operation that requires a string value.
Converting Dates to Strings
The convert function can also be used to convert date values to string values. This is useful when working with data that needs to be output in a particular format, or when dealing with data that needs to be displayed in a user interface.
To convert a date value to a string value using the convert function, you can use the following syntax:
SELECT CONVERT(VARCHAR, GETDATE(), 101)In this example, we are converting the current date and time to a string value using the convert function. The result of this operation will be a string value of ‘MM/DD/YYYY’, which is the standard date format in the United States.
Converting Strings to Dates
The convert function can also be used to convert string values to date values. This is useful when working with data that has been input in the wrong format, or when dealing with data that needs to be compared or used in calculations.
To convert a string value to a date value using the convert function, you can use the following syntax:
SELECT CONVERT(DATETIME, '05/23/2022', 101)In this example, we are converting the string value ’05/23/2022′ to a date value using the convert function. The result of this operation will be a date value of May 23, 2022, which can be used in any operation that requires a date value.
FAQs
What happens if I try to convert a string value to an integer value if the string is not a valid number?
If you try to convert a string value to an integer value using the convert function and the string is not a valid number, the operation will fail and an error will be returned. It’s important to make sure that the data you are converting is in the correct format before attempting to use the convert function.
Can I customize the format of the output when converting data types?
Yes, you can customize the format of the output when using the convert function to change data types. By specifying a format code as the third argument of the convert function, you can control the format of the output. For example, if you want to output a date in the format ‘YYYY/MM/DD’, you can use the following syntax:
SELECT CONVERT(VARCHAR, GETDATE(), 111)In this example, the format code 111 specifies that the date should be output in the format ‘YYYY/MM/DD’.
What happens if I try to convert a value to a data type that is too small to hold the value?
If you try to convert a value to a data type that is too small to hold the value, the operation will fail and an error will be returned. It’s important to make sure that the data type you are converting to is large enough to hold the value that you are converting.
Can I convert data types in a WHERE clause?
Yes, you can use the convert function to change data types in a WHERE clause. For example, if you have a column that contains string values that represent numbers, you can use the convert function to convert those values to numbers and then use them in a comparison. Here’s an example:
SELECT *FROM MyTableWHERE CONVERT(INT, MyColumn) > 42In this example, we are selecting all rows from the table MyTable where the value in the column MyColumn, when converted to an integer, is greater than 42.