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标题: 一个MYSQL的行转列的存储过程 [打印本页]

作者: kider 时间: 2007-10-8 14:02
标题: 一个MYSQL的行转列的存储过程
转载自：http://blog.chinaunix.net/u/29134/showart_364659.html

网上的都是一些静态的，用CASE WHEN结构实现。所以我写了一个动态的。

DELIMITER $$

DROP PROCEDURE IF EXISTS `test`.`sp_row_column_wrap`$$

CREATE DEFINER=`root`@`localhost` PROCEDURE `sp_row_column_wrap`(IN $schema_name varchar(64),
IN $table_name varchar(64))
BEGIN
  declare cnt int(11);
  declare $table_rows int(11);
  declare i int(11);
  declare j int(11);
  declare s int(11);
  declare str varchar(255);
  -- Get the column number of the table
  select count(1) from information_schema.columns where table_schema=$schema_name and table_name=$table_name into cnt;
  -- Get the row number of the table
  select table_rows from information_schema.tables where table_schema = $schema_name and table_name=$table_name into $table_rows;
  -- Check whether the table exists or not
  drop table if exists test.temp;
  create table if not exists test.temp (`1` varchar(255) not null);
  -- loop1 start
  set i = 0;
  loop1:loop
if i = $table_rows-1 then
   leave loop1;
end if;
set @stmt1 = concat('alter table test.temp add `',i+2,'` varchar(255) not null');
prepare s1 from @stmt1;
execute s1;
deallocate prepare s1;
set i = i + 1;
  end loop loop1;
  -- loop1 end;
  set s = 0;
  -- loop2 start
  loop2:loop
  -- leave loop2
if s=cnt then
   leave loop2;
end if;
set @stmt2 = concat('select column_name from information_schema.columns where table_schema="',$schema_name,
                     '" and table_name="',$table_name,'" limit ',s,',1 into @temp;');
prepare s2 from @stmt2;
execute s2;
deallocate prepare s2;

set j=0;
set str = ' select ';
-- Loop3 start
loop3:loop
   if j = $table_rows then
      leave loop3;
   end if;
   set @stmt3 = concat('select ',@temp,' from ',$schema_name,'.',$table_name,' limit ',j,',1 into @temp2;');
   prepare s3 from @stmt3;
   execute s3;
   set str = concat(str,'"',@temp2,'"',',');
   deallocate prepare s3;
   set j = j+1;
end loop loop3;
set str = left(str,length(str)-1);
-- insert new data into table
set @stmt4 = concat('insert into test.temp',str,';');
prepare s4 from @stmt4;
execute s4;
deallocate prepare s4;
set s=s+1;
  end loop loop2;
END$$

DELIMITER ;
以下是测试结果：
======
select * from a;
select * from b;
select * from salary;

call sp_row_column_wrap('test','a');
select * from test.temp;
call sp_row_column_wrap('test','b');
select * from test.temp;
call sp_row_column_wrap('test','salary');
select * from test.temp;

query result(2 records)

aid	title
1	111
2	222

query result(3 records)

bid	aid	image	time
1	2	1.gif	2007-08-08
2	2	2.gif	2007-08-09
3	2	3.gif	2007-08-08

query result(7 records)

id	cost	des	Autoid
1	10	aaaa	1
1	15	bbbb	2
1	20	cccc	3
2	80	aaaa	4
2	100	bbbb	5
2	60	dddd	6
3	500	dddd	7

query result(2 records)

1	2
1	2
111	222

query result(4 records)

1	2	3
1	2	3
2	2	2
1.gif	2.gif	3.gif
2007-08-08	2007-08-09	2007-08-08

query result(4 records)

1	2	3	4	5	6	7
1	1	1	2	2	2	3
10	15	20	80	100	60	500
aaaa	bbbb	cccc	aaaa	bbbb	dddd	dddd
1	2	3	4	5	6	7

作者: drekey 时间: 2007-10-15 19:18
写的不错，支持，呵呵！

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