Ever have a table with a ton of columns some of which aren't used?

Below is a procedure to drop empty columns from a MySQL table:

CREATE PROCEDURE dropEmptyColumns(dbName varchar(64), tableName varchar(64), drop_log text)  
LANGUAGE SQL  
DETERMINISTIC  
CONTAINS SQL  
SQL SECURITY DEFINER  
COMMENT ''  
BEGIN





  DECLARE done INT DEFAULT FALSE;  
  DECLARE col_name varchar(256);





  -- Get Column Names  
  DECLARE column_cur CURSOR FOR  
      SELECT COLUMN_NAME  
      FROM `information_schema`.`COLUMNS`  
        WHERE (`TABLE_SCHEMA` = dbName)  
          AND (`TABLE_NAME` = tableName);  
  DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;





  SET @amount = -1;  
  SET @tableName = tableName;  
  SET @dbname = dbName;  
  SET @drop_log = '';  
  SET @testSql = '';





  -- For each column name  
  OPEN column_cur;  
  check_column_loop: LOOP





    -- SELECT 'IN LOOP' INTO @drop_log;  
    FETCH column_cur INTO col_name;





    -- Break loop if no more rows  
    IF done THEN  
      LEAVE check_column_loop;  
    END IF;  
      
    -- Build the query, with dynamic table and column. Store the result in @amount  
    SELECT CONCAT('SELECT COUNT(', col_name ,') INTO @amount FROM ', @tableName ,' WHERE(', col_name ,' IS NOT NULL OR ', col_name ,' != "");') INTO @testSql;  
    PREPARE testSqlStmt FROM @testSql;





    -- Execute  
    EXECUTE testSqlStmt;





    -- Check if we have 0 rows, else we still have data and we do not want to drop.  
    IF @amount = 0 THEN  
          
      -- Build the query  
      SELECT CONCAT('ALTER TABLE ', @tableName ,' DROP COLUMN ', col_name ,';') INTO @alterSql;





      -- Execute  
      PREPARE alterSqlStmt FROM @alterSql;  
      EXECUTE alterSqlStmt;  
                  
      -- Append Log  
      SELECT CONCAT(@drop_log, col_name, ' DROPPED\r\n') INTO @drop_log;





    END IF;





  END LOOP;  
  CLOSE column_cur;





END  

Once you have created the procedure you can run it like this:

CALL dropEmptyColumns('', '', @drop_log);  
SELECT @drop_log;