SQL - TRY_CONVERT() Function

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The SQL TRY_CONVERT() function tries to change the datatype of an expression. In case of unsuccessful conversion, the function will return NULL. If not, it will give you the converted value.

The only difference between the TRY_CONVERT() and CONVERT() functions is when the conversion is failed. CONVERT() throws an error whereas TRY CONVERT() returns a NULL.

Syntax

Following is the syntax of the SQL TRY_CAST() function −

TRY_CONVERT ( data_type [ ( length ) ], expression [, style ] )

Parameters

This function accepts only four parameter. The same is described below −

  • expression − the valid expression that to be convert to data type.

  • datatype − It is the datatype that we want to convert the expression to.

  • length − It was used to define the length of any targeted data type, as it was an optional parameter of an integer type. the default value is 30.

  • style − It was the optional integer expression and specifies how TRY_CONVERT() function translates the given expression

Example

Let us try to convert the string to decimal with TRY_CONVERT() function by using the following query −

SELECT TRY_CONVERT(DECIMAL(6,2), '1234.5') AS Result;

Output

When we execute the above query, the output is obtained as follows −

+------------------------------------+
|                              Result|
+------------------------------------+
|                            1234.50 |
+------------------------------------+

Example

Let's try to convert the string of valid date to datetime2 type by using the following query −

SELECT TRY_CONVERT (datetime2, '2023-02-23') AS Result;

Output

On executing the above query, the output is displayed as follows −

+------------------------------------+
|                              Result|
+------------------------------------+
|         2023-02-23 00:00:00.0000000|
+------------------------------------+

Example

Considering the following example, where we are going to convert the string to decimal, It will return NULL as it was unable to convert the string 1234.45 to decimal (3, 2). Let's check by using the below query −

SELECT TRY_CONVERT(decimal(3,2), '1234.45') AS Result;

Output

On executing the above query, the output is displayed as follows −

+------------------------------------+
|                              Result|
+------------------------------------+
|                               NULL |
+------------------------------------+

Example

Let's look into the following example, where we are using the style parameter to specify how the expression is translated and running the below queries −

SET LANGUAGE British;
SELECT 
   TRY_CONVERT(date, '02/23/2023', 101) AS "US",
   TRY_CONVERT(date, '20230223', 112) AS "ISO",
   TRY_CONVERT(date, '02/23/23', 1) AS "US (short)";

Output

The output for the above query is produced as given below − 

+-------------------+----------------+---------------+
|                US |          ISO   |  US(short)    |   
+-------------------+----------------+---------------+
|     2023-02-23    |     2023-02-23 | 2023-02-23    |
+-------------------+----------------+---------------+

Example

Look at the following example, where we are going to convert the expression to the varchar and mentioning the style by using the following query −

SELECT TRY_CONVERT(varchar, '2023-02-23', 101) AS Result;

Output

If we compile and run the above query, the result is produced as follows −

+------------------------------------+
|                              Result|
+------------------------------------+
|                         2023-02-23 |
+------------------------------------+

Example

let's look into the following example, where TRY_CONVERT() function return an error when the conversion is explicitly not permitted using the following query −

SELECT TRY_CONVERT(xml, 2) AS Result;

Output

On executing the above query, it will generate the following output as shown below −

Explicit conversion from data type int to xml is not allowed.

Example

Let’s consider another example, where we are going to use the TRY_CONVERT()function with case and running the following query −

SELECT 
CASE WHEN TRY_CAST('TUTORIALSPOINT' AS int) IS NOT NULL
   THEN 'CastFailed'  
      ELSE 'CastSucceeded'  
END AS Result;

Output

When the query gets executed, it will generate the output as shown below −

+------------------------------------+
|                              Result|
+------------------------------------+
|                      CastSucceeded |
+------------------------------------+

Example

Considering the following example, where we are converting the expression to an int, which makes the value get truncated by using the following query −

SELECT TRY_CONVERT(int, 12.34) AS Result;

Output

When we execute the above query, the output is obtained as follows −

+------------------------------------+
|                              Result|
+------------------------------------+
|                                 12 |
+------------------------------------+
sql-conversion-functions.htm
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