How to Handle Global Input Parameters in T-SQL Stored Procedures When Executing Dynamic SQL?

Trouble with Global Input Parameters and SQL Execution

In a stored procedure that compiles an SQL query with T-SQL and executes it using EXEC (@sqlstatement), you may encounter an error stating "Must declare the scalar variable "@RowFrom"." when attempting to use global input parameters @RowFrom and @RowTo within the @sqlstatement variable.

Understanding the Issue

The error occurs because the parameters @RowFrom and @RowTo are not recognized within the @sqlstatement string. This is because SQL strings cannot directly access global variables without explicit declaration.

Solution: Converting Int to String or Using Proper Parameterization

There are two approaches to resolve this issue:

1. Convert Int to String: To pass the integer value of @RowTo as a string, use the CONVERT function:

SET @sql = N'DECLARE @Rt int; SET @Rt = ' + CONVERT(VARCHAR(12), @RowTo);

2. Use Proper Parameterization: Rather than concatenating values into the SQL string, use parameterized queries to pass input parameters securely. For example:

SET @sql = @sql + ' WHERE RowNum BETWEEN @RowFrom AND @RowTo;';

EXEC sys.sp_executesql @sql,
  N'@RowFrom int, @RowTo int',
  @RowFrom, @RowTo;

Consideration for Modern Versions

In modern versions of SQL, you can use the CONCAT function for string concatenation:

SET @sql = CONCAT(N'SELECT ', @RowTo, ' * 5');

However, it's recommended to use proper parameterization to prevent SQL injection vulnerabilities.

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