Bạn có thể sử dụng một thủ tục được lưu trữ sử dụng con trỏ để giải quyết vấn đề này nhưng nó không đẹp lắm nhưng cũng không phải là danh sách người viết được phân tách bằng dấu phẩy!
Có mã sau nằm xung quanh một câu hỏi tương tự nhưng tốt hơn bạn nên kiểm tra kỹ lưỡng.
Hy vọng nó sẽ giúp :)
mysql> select * from movies_unf;
+---------+-------------+------------------------------------------------------+
| movieID | movie_title | written_by |
+---------+-------------+------------------------------------------------------+
| 1 | movie1 | person1, person2 |
| 2 | movie2 | person3 |
| 3 | movie3 | person4, person2, person6 |
| 4 | movie4 | person4, person4, person1, person2, person1,person8, |
| 5 | movie1 | person1, person2 |
+---------+-------------+------------------------------------------------------+
5 rows in set (0.00 sec)
call normalise_movies_unf();
mysql> select * from movies;
+----------+--------+
| movie_id | title |
+----------+--------+
| 1 | movie1 |
| 2 | movie2 |
| 3 | movie3 |
| 4 | movie4 |
+----------+--------+
4 rows in set (0.00 sec)
mysql> select * from writers;
+-----------+---------+
| writer_id | name |
+-----------+---------+
| 1 | person1 |
| 2 | person2 |
| 3 | person3 |
| 4 | person4 |
| 6 | person6 |
| 12 | person8 |
+-----------+---------+
6 rows in set (0.00 sec)
mysql> select * from movie_writers;
+----------+-----------+
| movie_id | writer_id |
+----------+-----------+
| 1 | 1 |
| 1 | 2 |
| 2 | 3 |
| 3 | 2 |
| 3 | 4 |
| 3 | 6 |
| 4 | 1 |
| 4 | 2 |
| 4 | 4 |
| 4 | 12 |
+----------+-----------+
10 rows in set (0.00 sec)
Bảng mẫu
drop table if exists movies_unf;
create table movies_unf
(
movieID int unsigned not null primary key,
movie_title varchar(255) not null,
written_by varchar(1024) not null
)engine=innodb;
insert into movies_unf values
(1,'movie1','person1, person2'),
(2,'movie2','person3'),
(3,'movie3','person4, person2, person6'),
(4,'movie4','person4, person4, person1, person2, person1,person8,'), -- dodgy writers
(5,'movie1','person1, person2'); -- dodgy movie
drop table if exists movies;
create table movies
(
movie_id int unsigned not null auto_increment primary key,
title varchar(255) unique not null
)engine=innodb;
drop table if exists writers;
create table writers
(
writer_id int unsigned not null auto_increment primary key,
name varchar(255) unique not null
)engine=innodb;
drop table if exists movie_writers;
create table movie_writers
(
movie_id int unsigned not null,
writer_id int unsigned not null,
primary key (movie_id, writer_id)
)engine=innodb;
Quy trình được lưu trữ
drop procedure if exists normalise_movies_unf;
delimiter #
create procedure normalise_movies_unf()
begin
declare v_movieID int unsigned default 0;
declare v_movie_title varchar(255);
declare v_writers varchar(1024);
declare v_movie_id int unsigned default 0;
declare v_writer_id int unsigned default 0;
declare v_name varchar(255);
declare v_csv_done tinyint unsigned default 0;
declare v_csv_idx int unsigned default 0;
declare v_done tinyint default 0;
declare v_cursor cursor for
select distinct movieID, movie_title, written_by from movies_unf;
declare continue handler for not found set v_done = 1;
start transaction;
open v_cursor;
repeat
fetch v_cursor into v_movieID, v_movie_title, v_writers;
set v_movie_title = trim(v_movie_title);
set v_writers = replace(v_writers,' ', '');
-- insert the movie
insert ignore into movies (title) values (v_movie_title);
select movie_id into v_movie_id from movies where title = v_movie_title;
-- split the out the writers and insert
set v_csv_done = 0;
set v_csv_idx = 1;
while not v_csv_done do
set v_name = substring(v_writers, v_csv_idx,
if(locate(',', v_writers, v_csv_idx) > 0,
locate(',', v_writers, v_csv_idx) - v_csv_idx,
length(v_writers)));
set v_name = trim(v_name);
if length(v_name) > 0 then
set v_csv_idx = v_csv_idx + length(v_name) + 1;
insert ignore into writers (name) values (v_name);
select writer_id into v_writer_id from writers where name = v_name;
insert ignore into movie_writers (movie_id, writer_id) values (v_movie_id, v_writer_id);
else
set v_csv_done = 1;
end if;
end while;
until v_done end repeat;
close v_cursor;
commit;
truncate table movies_unf;
end#
delimiter ;
CHỈNH SỬA
Cải tiến đã được sửa đổi để nó không bỏ qua các giá trị chính!
drop procedure if exists normalise_movies_unf;
delimiter #
create procedure normalise_movies_unf()
begin
declare v_movieID int unsigned default 0;
declare v_movie_title varchar(255);
declare v_writers varchar(1024);
declare v_movie_id int unsigned default 0;
declare v_writer_id int unsigned default 0;
declare v_name varchar(255);
declare v_csv_done tinyint unsigned default 0;
declare v_csv_idx int unsigned default 0;
declare v_done tinyint default 0;
declare v_cursor cursor for
select distinct movieID, movie_title, written_by from movies_unf;
declare continue handler for not found set v_done = 1;
start transaction;
open v_cursor;
repeat
fetch v_cursor into v_movieID, v_movie_title, v_writers;
set v_movie_title = trim(v_movie_title);
set v_writers = replace(v_writers,' ', '');
-- insert the movie
if not exists (select 1 from movies where title = v_movie_title) then
insert ignore into movies (title) values (v_movie_title);
end if;
select movie_id into v_movie_id from movies where title = v_movie_title;
-- split the out the writers and insert
set v_csv_done = 0;
set v_csv_idx = 1;
while not v_csv_done do
set v_name = substring(v_writers, v_csv_idx,
if(locate(',', v_writers, v_csv_idx) > 0,
locate(',', v_writers, v_csv_idx) - v_csv_idx,
length(v_writers)));
set v_name = trim(v_name);
if length(v_name) > 0 then
set v_csv_idx = v_csv_idx + length(v_name) + 1;
if not exists (select 1 from writers where name = v_name) then
insert ignore into writers (name) values (v_name);
end if;
select writer_id into v_writer_id from writers where name = v_name;
insert ignore into movie_writers (movie_id, writer_id) values (v_movie_id, v_writer_id);
else
set v_csv_done = 1;
end if;
end while;
until v_done end repeat;
close v_cursor;
commit;
truncate table movies_unf;
end#
delimiter ;
