To add a column if it does not exist you can do a Prepare/Execute function as follows:

SET @dbname = DATABASE();
SET @tablename = "tableName";
SET @columnname = "colName";
SET @preparedStatement = (SELECT IF(
  (
    SELECT COUNT(*) FROM INFORMATION_SCHEMA.COLUMNS
    WHERE
      (TABLE_NAME = @tablename)
      AND (table_schema = @dbname)
      AND (column_name = @columnname)
  ) > 0,
  "SELECT 1",
  CONCAT("ALTER TABLE ", @tablename, " ADD ", @columnname, " INT(11);")
));
PREPARE alterIfNotExists FROM @preparedStatement;
EXECUTE alterIfNotExists;
DEALLOCATE PREPARE alterIfNotExists;

Other ways of doing this are available in the discussion at https://stackoverflow.com/questions/24571611/mysql-alter-table-if-column-not-exists

• https://stackoverflow.com/questions/24571611/mysql-alter-table-if-column-not-exists