写了一个MySQL的行转列的存储过程

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




本文转自 yarin 51CTO博客,原文链接:http://blog.51cto.com/yueliangdao0608/80493,如需转载请自行联系原作者

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