BEGIN
    -- convert BYTE > CHAR
    FOR rec IN
        (SELECT owner, table_name, column_name, data_length 
        FROM all_TAB_COLUMNS 
        WHERE owner = 'ALLIANCE'
        AND data_type= 'VARCHAR2'
        AND char_used = 'B')
    LOOP
        EXECUTE IMMEDIATE 'ALTER TABLE ALLIANCE.'||rec.table_name||' MODIFY '||rec.column_name||' VARCHAR2('||rec.data_length||' CHAR)';
    END LOOP;
END;