Structured Query Language (SQL) is a domain-specific language utilized for managing, storing, and organizing relational databases. The SQL Server TRY_CAST() function is a powerful tool used in SQL for data type conversion.
This function is different from the CAST() function as it can handle data conversions that might produce errors by returning a NULL value instead of throwing an error. The TRY_CAST() function can streamline the conversion of data types and drastically reduce the chances of errors.
In this article, we will provide an overview of the syntax of TRY_CAST(), its arguments and behavior, and compare it with the CAST() function. We will also explore how TRY_CAST() handles NULL values and errors, and how one can troubleshoot such issues.
Syntax of TRY_CAST()
The TRY_CAST() function is an SQL Server function that tries to convert an expression of one data type to another. If the conversion can be performed, it returns the converted value; otherwise, it returns a NULL value.
The syntax for the TRY_CAST() function is as follows:
TRY_CAST(expression as data_type)
Here, the expression is the value, variable, or a column that needs to be converted, and data_type is the target data type. For example:
SELECT TRY_CAST('245A' as INT) as Result;In the above example, we are trying to convert the string value ‘245A’ into an integer using TRY_CAST().
Since this string value cannot be converted into an integer because of the alphabetic character, TRY_CAST() function will return a NULL value.
Arguments of TRY_CAST()
The TRY_CAST() function has two primary arguments: the expression and the data_type to which the expression needs to be cast.
The expression argument can either be a literal value or a variable. The data_type argument specifies the data type that the expression needs to be cast into.
The data_type argument can be any of the SQL Server data types, such as INT, VARCHAR, NVARCHAR, etc.
Behavior of TRY_CAST()
The TRY_CAST() function tries to convert a given expression into the target data_type.
If the conversion is successful, the function returns the converted value. If it is not possible to convert the expression into the target data_type, the function returns a NULL value.
This is significantly different from the CAST() function, which, if unable to perform the conversion, throws an error.
TRY_CAST() vs CAST()
The primary difference between TRY_CAST() and CAST() is the handling of errors and NULLs. TRY_CAST() is designed to handle data conversions that may produce errors.
If it cannot perform the conversion, it simply returns a NULL value. On the other hand, CAST() will result in an error if the conversion cannot be performed.
Handling NULLs and Errors in TRY_CAST()
Since TRY_CAST() returns a NULL when an error is encountered, it is essential to handle NULLs properly in SQL queries. One way to handle NULL values in TRY_CAST() is by using the ISNULL() or COALESCE functions.
The ISNULL() function checks if the value is NULL, and if it is, it replaces it with a specified default value. COALESCE is similar to ISNULL(), except it can be used with multiple arguments.
Another way to handle NULL values is through the use of the CASE statement. Additionally, if there are issues with conversion, the TRY…CATCH statement can be used to catch and handle errors and then take corrective action.
Conclusion
In conclusion, the TRY_CAST() function is a valuable tool for data conversion in SQL Server. It can handle conversions that may produce errors and reduce chances of failures.
We have provided an overview of the syntax of the TRY_CAST() function, its arguments and behavior, and compared it with the CAST() function. We have also discussed how TRY_CAST() handles NULL values and errors, and how they can be handled using various functions and statements in SQL.
Being proficient in the use of TRY_CAST() and its related functions can save a lot of time and effort in dealing with data conversions in SQL. TRY_CAST() is a powerful SQL Server function that ensures that data type conversions are successful, often avoiding errors that can be time-consuming to debug.
TRY_CAST() Returning NULL
One example of how TRY_CAST() can be of use is when you need to convert a value, but the conversion would result in an error. If you try to apply CAST() instead of TRY_CAST() in this situation, it will raise an error.
The TRY_CAST(), on the other hand, will return NULL instead of raising an error. This is a valuable feature of TRY_CAST() as it provides a way to avoid errors during data type conversions.
Consider the following SQL code:
SELECT TRY_CAST('Hello' AS INT) AS Result;In the above example, we are attempting to convert the string ‘Hello’ to an integer using TRY_CAST(). Since the string Hello cannot be converted to an integer, TRY_CAST() will return a NULL value.
TRY_CAST() Raising an Error
In some cases, the TRY_CAST() function might still raise an error. For example, if the data value to be converted is not compatible with the target data type provided in the function, it will raise an error.
Consider the following example:
SELECT TRY_CAST(‘abc’ AS DATETIME) AS Result
In the above example, we are attempting to convert the string value ‘abc’ to a datetime data type using TRY_CAST(). Since the string value is not a valid value for the DATETIME data type, the TRY_CAST() function will raise an error.
Converting a String to Decimal with TRY_CAST()
The TRY_CAST() function is also effective in converting a string to a decimal. Consider the following examples:
SELECT TRY_CAST('100.50' AS DECIMAL(5,2)) AS Result;In the above example, we are attempting to convert the string 100.50 to a decimal (5,2) data type using TRY_CAST().
Since the string is compatible with the decimal (5,2) data type, the TRY_CAST() function will return the result as 100.50.
Converting a String to Integer with TRY_CAST()
In some cases, you may need to convert a string to an integer data type. In such cases, the TRY_CAST() function comes in handy.
Consider the following examples:
SELECT TRY_CAST('500' AS INT) AS Result;In the above example, we are trying to convert the string 500 to integer data type using TRY_CAST(). Since the string is compatible with integer data type, the TRY_CAST() function will return the result as 500.
Converting DateTime to Date or Time with TRY_CAST()
Another common use of TRY_CAST() is in converting datetime data types to date or time data types. SQL Server provides the DATE and TIME data types to store only date and time values, respectively.
Consider the following examples:
SELECT TRY_CAST('2021-09-17 17:15:30' AS DATE) AS DateResult;In the above example, we are trying to convert the datetime value ‘2021-09-17 17:15:30’ into a DATE data type. Since datetime values include both date and time, we can only convert it to date with TRY_CAST().
The TRY_CAST() function will extract the date from the datetime value and convert that to the DATE data type.
SELECT TRY_CAST('2021-09-17 17:15:30.0000000' AS TIME) AS TimeResult;In the above example, we are attempting to convert the datetime value ‘2021-09-17 17:15:30’ to a TIME data type using TRY_CAST().
Since datetime values include both date and time, we can only extract the time portion using TRY_CAST().
Conclusion
In conclusion, TRY_CAST() is a valuable SQL Server function designed to help with data type conversions. It ensures that data type conversions are successful by returning NULL instead of an error when it cannot coerce the conversion.
This reduces potential errors and ensures that your SQL code runs smoothly. In this article, we have seen how the TRY_CAST() function can handle returning NULL and raising an error while converting various data types such as string to decimal, string to integer, and datetime to date or time.
In conclusion, TRY_CAST() is a powerful SQL Server function designed to help with data type conversions. It is a valuable tool as it reduces potential errors and ensures that your SQL code runs smoothly.
In this article, we provided an overview of the TRY_CAST() function’s syntax and compared it with the CAST() function. We also demonstrated how TRY_CAST() can handle returning NULL and raising an error while converting various data types such as string to decimal, string to integer, and datetime to date or time.
Being proficient in the use of TRY_CAST() and related functions saves time and effort in dealing with data conversions in SQL. It is essential to understand the features and limitations of TRY_CAST() and its potential to handle errors and increase efficiency.