This generates one SQL to be used to move one database tables to other database

generate_sql_to_move_all_tables_from_one_database_to_other.sql

# Change these variables values
set @old_db='a';
set @new_db='b';
SET SESSION group_concat_max_len = 1000000;

# Don't change anything below
SELECT CONCAT('RENAME TABLE ' , GROUP_CONCAT(cmd SEPARATOR ', ')) 'sql' 
  FROM ( 
    SELECT CONCAT('`',@old_db,'`.`', TABLE_NAME, '` TO `',@new_db,'`.`', TABLE_NAME, '`') cmd 
    FROM information_schema.tables 
    WHERE TABLE_SCHEMA = @old_db
  ) a 
  LIMIT 1;