The TRY_PARSE function in SQL Server is used to convert a string representation of a date or number into a date data type or a numeric data type, respectively, while also providing error handling. If the string cannot be converted, TRY_PARSE will return NULL instead of throwing an error. This makes it a useful function for situations where you want to handle potential conversion errors gracefully.
Syntax
The basic syntax of the TRY_PARSE function is:
TRY_PARSE ( string_value AS data_type [ USING culture ] )
- string_value: The string you want to convert.
- data_type: The target data type you want the string to be converted to (DATETIME, DATE, TIME, FLOAT, DECIMAL, etc.).
- culture: (Optional) A string that specifies the culture information that is used to interpret the string. This can be useful for date formats or number formats that vary by culture.
Examples
Example 1: Converting a String to a Date
DECLARE @DateString NVARCHAR(50) = '2023-10-31';
SELECT
TRY_PARSE(@DateString AS DATETIME) AS ResultDate,
TRY_PARSE('invalid-date' AS DATETIME) AS InvalidResultDate; -- This will return NULL
In this example, @DateString is successfully converted to a date, while the invalid date string returns NULL.
Example 2: Converting a String to a Numeric Type
DECLARE @NumberString NVARCHAR(50) = '123.45';
SELECT
TRY_PARSE(@NumberString AS FLOAT) AS ResultNumber,
TRY_PARSE('invalid-number' AS FLOAT) AS InvalidNumber; -- This will return NULL
Here, @NumberString successfully converts to a FLOAT, but the invalid string results in NULL.
Example 3: Using Culture Parameter
DECLARE @DateString NVARCHAR(50) = '10/31/2023';
SELECT
TRY_PARSE(@DateString AS DATETIME USING 'en-US') AS US_Date,
TRY_PARSE(@DateString AS DATETIME USING 'fr-FR') AS FR_Date; -- Incorrect format for 'fr-FR', returns NULL.
In this example, the date string is parsed correctly using U.S. culture, but it returns NULL for the French culture format.
Important Notes
1. NULL Handling: Because TRY_PARSE returns NULL on failure, you can easily check for conversion success or failure using ISNULL or COALESCE functions.
2. Performance: Using TRY_PARSE may have some performance implications compared to other conversion functions (like CAST and CONVERT) because it involves more complex parsing.
3. Supported Formats: The formats for date and numbers may vary depending on the culture specified, so it's important to ensure that the input strings conform to the expected formats for the specified culture.
By using TRY_PARSE, you can safely attempt to convert strings into dates or numbers while handling potential errors effectively.