How sql server convert varchar to int?

In SQL Server, you can convert a VARCHAR value to an INT using CAST(), CONVERT(), or TRY_CONVERT() functions. Here’s how:

1. Using CAST() (Standard SQL)

  SELECT CAST('123' AS INT) AS ConvertedValue;

• Converts '123' to 123 as an integer.
  
• If the value is non-numeric, it throws an error.
  

2. Using CONVERT() (SQL Server Specific)

  SELECT CONVERT(INT, '123') AS ConvertedValue;

• Works similarly to CAST().
  
• Allows specifying different data types, e.g., CONVERT(FLOAT, '123.45').
  

3. Using TRY_CONVERT() (Safe Conversion)

SELECT TRY_CONVERT(INT, '123') AS ConvertedValue;
SELECT TRY_CONVERT(INT, 'ABC') AS ConvertedValue; -- Returns NULL

• Returns NULL if conversion fails, preventing errors.
  
• Useful for handling invalid numeric values safely.
  

4. Handling Non-Numeric Values

If your column contains mixed data, filter numeric values before conversion:

SELECT CAST(Value AS INT) 
FROM TableName 
WHERE ISNUMERIC(Value) = 1;

OR

Using TRY_CAST() to avoid errors:

  SELECT TRY_CAST(Value AS INT) FROM TableName;

Best Practices

✔ Use TRY_CONVERT() or TRY_CAST() for safe conversions.

✔ Ensure data contains only numeric values before conversion.

✔ Handle NULL or invalid values properly to avoid runtime errors.

Would you like an example with real-world data?

In SQL Server, you can convert a varchar (or any other compatible data type) to an int using the CAST or CONVERT functions. Here's how you can do it:

  SELECT CAST('123' AS INT) AS ConvertedValue;

Using CONVERT:

SELECT CONVERT(INT, '123') AS ConvertedValue;

Both methods will convert the string '123' to an integer value of 123. Make sure that the varchar value you are converting can be safely cast to an int. If the varchar value contains non-numeric characters, or if it exceeds the range of valid integer values, the conversion will fail, and you may encounter errors.