How to Iterate Through MySQL Column Names Using Native SQL?

Iterating Through Column Names in MySQL using Native SQL

To retrieve and iterate through column names in a MySQL table using SQL, consider employing the following approach:

1. Retrieving the Column Names

Utilize the SHOW COLUMNS FROM [table_name] statement to retrieve a list of all column names within the specified table. This command yields a result set where each row represents a single column and contains metadata such as the column name.

SHOW COLUMNS FROM table_name;

2. Creating a Cursor

To enable iterative processing of the column names, create a cursor using the DECLARE col_names CURSOR FOR syntax, where col_names represents the name of the cursor. Inside the cursor definition, specify a query to retrieve the column names, ensuring they are ordered by their ordinal positions.

DECLARE col_names CURSOR FOR
SELECT column_name
FROM INFORMATION_SCHEMA.COLUMNS
WHERE table_name = 'table_name'
ORDER BY ordinal_position;

3. Determining the Number of Columns

To facilitate loop control, execute the FOUND_ROWS() function and store the result in a variable, num_rows. This value represents the total number of rows (and therefore columns) retrieved by the cursor query.

SELECT FOUND_ROWS() INTO num_rows;

4. Iterating Over the Columns

Enter the loop using the SET i = 1 statement, where i is an iterator variable initialized to 1. Inside the loop, utilize the FETCH col_names INTO col_name statement to retrieve each column name sequentially into the col_name variable.

SET i = 1;
the_loop: LOOP

   IF i > num_rows THEN
        CLOSE col_names;
        LEAVE the_loop;
    END IF;


    FETCH col_names 
    INTO col_name;     //do whatever else you need to do with the col name

    SET i = i + 1;  
END LOOP the_loop;

5. Executing Stored Procedures

Within the loop, you can optionally execute stored procedures using the column names as variables. For instance, the following statement invokes a stored procedure named sp_my_proc, passing the col_name as a parameter:

CALL sp_my_proc(col_name);

6. Closing the Cursor

After completing the loop, close the cursor using the CLOSE statement to release any associated resources:

CLOSE col_names;

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