Dynamic SQL refers to constructing and executing SQL statements dynamically at runtime. It is useful when the SQL statement or its parameters need to be determined at runtime or when building generic procedures.

Why use dynamic SQL in SQL stored procedures?

Dynamic SQL allows you to create SQL statements on the fly, providing flexibility and adaptability in your code. It enables you to handle complex queries with dynamic filtering, sorting, or column selections based on changing requirements. Dynamic SQL is commonly used for executing dynamic search queries, generating reports, and building flexible database-driven applications.

Syntax for using dynamic SQL in SQL stored procedures

In SQL, dynamic SQL can be implemented using the EXECUTE or EXEC statement. Here’s a basic syntax to follow:

CREATE PROCEDURE <procedure_name>
AS
BEGIN
    DECLARE @sqlStatement NVARCHAR(MAX)

    -- Build your dynamic SQL statement here
    SET @sqlStatement = 'SELECT * FROM <table_name> WHERE <condition>'

    -- Execute the dynamic SQL statement
    EXECUTE sp_executesql @sqlStatement
END

Make sure to replace <procedure_name>, <table_name>, and <condition> with appropriate values in your code.

Example usage of dynamic SQL in SQL stored procedures

Let’s consider an example where we want to search for employees in a table based on dynamically provided search criteria. We’ll use the Employee table consisting of columns like Name, Department, and Salary.

CREATE PROCEDURE SearchEmployees
    @searchTerm NVARCHAR(50)
AS
BEGIN
    DECLARE @sqlStatement NVARCHAR(MAX)

    -- Build the dynamic SQL statement
    SET @sqlStatement = 'SELECT * FROM Employee WHERE Name LIKE ''%' + @searchTerm + '%'''

    -- Execute the dynamic SQL statement
    EXECUTE sp_executesql @sqlStatement
END

In this example, the parameter @searchTerm is used to dynamically search for employees whose names contain the provided search term. The % symbols are used as wildcards to match any characters before and after the search term.

Conclusion

Dynamic SQL provides a powerful mechanism to dynamically construct and execute SQL statements at runtime within SQL stored procedures. By using this approach, you can enhance the flexibility and adaptability of your code, enabling it to handle changing requirements efficiently.

Using dynamic SQL within SQL stored procedures should be done with caution. Always validate and sanitize user inputs to prevent potential SQL injection attacks.

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