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)
aidtitle11112222query result(3 records)
bidaidimagetime121.gif2007-08-08222.gif2007-08-09323.gif2007-08-08query result(7 records)
idcostdesAutoid110aaaa1115bbbb2120cccc3280aaaa42100bbbb5260dddd63500dddd7query result(2 records)
1212111222query result(4 records)
1231232221.gif2.gif3.gif2007-08-082007-08-092007-08-08query result(4 records)
123456711122231015208010060500aaaabbbbccccaaaabbbbdddddddd1234567
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