[原创]写了一个MYSQL的行转列的存储过程。 - SQL语句与特殊技巧

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。

SP 代码：

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 = $table_rows-1 then
      leave loop1;
    end if;
    set @stmt1 = concat('alter table test.temp add `',i+2,'` varchar(255) not null');
    prepare s1 from @stmt1;
    execute s1;
    deallocate prepare s1;
    set @stmt1 = '';
    set i = i + 1;
  end loop loop1;
  -- loop1 end;
  set s = 0;
  -- loop2 start
  loop2:loop
  -- leave loop2
    if s=cnt then
      leave loop2;
    end if;
    set @stmt2 = concat('select column_name from information_schema.columns where table_schema="',$schema_name,
                        '" and table_name="',$table_name,'" limit ',s,',1 into @temp;');
    prepare s2 from @stmt2;
    execute s2;
    deallocate prepare s2;

set @stmt2 = '';

    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 @stmt3 = '';
      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 @stmt4 = '';
    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