MySql 行转列 存储过程实现

同学们在使用mysql的过程中，会遇到一个行转列的问题，就是把多条数据转化成一条数据 用多列显示。

方法1. 实现方式用下面的存储过程，表名对应的修改就行。

BEGIN
declare current integer;
declare strValue tinytext ;
declare sqlValue BLOB;
declare columnCount int(4);
declare countNum INTEGER;
declare pageNumber INTEGER;
declare firstNumber integer;
set current = 0;
set countNum=0;
set columnCount=0;
set pageNumber=0;
set firstNumber=0;
drop table if exists personal_contact_temp;
CREATE TABLE `personal_contact_temp` (
`id` varchar(64) NOT NULL COMMENT '主键',
`personal_id` varchar(64) ,
`relation` int(4) ,
`name` TEXT ,
`phone` TEXT ,
`phone_status` int(4) ,
`mobile` TEXT ,
PRIMARY KEY (`id`)
) ENGINE=InnoDB ROW_FORMAT=COMPRESSED KEY_BLOCK_SIZE=8 DEFAULT CHARSET=utf8 COMMENT='客户信息联系人临时表';

set columnCount=(select max(conNum) from (select count(*) as conNum from personal_contact GROUP BY personal_id) b);
set current =(select count(*) from (select count(*) as countNum from personal_contact GROUP BY personal_id) b);
while columnCount>0 do
begin
set sqlValue='';
set sqlValue= CONCAT('alter TABLE personal_contact_temp add COLUMN relation',columnCount,'A',' INT(4),',
'add COLUMN name',columnCount,'A',' VARCHAR(255),',
'add COLUMN phone',columnCount,'A',' varchar(255),',
'add COLUMN phone_status',columnCount,'A',' int(4),',
'add COLUMN mobile',columnCount,'A',' VARCHAR(255)',';');
set @ms=sqlValue;
PREPARE stmt1 FROM @ms;
EXECUTE stmt1;
END;
set columnCount=columnCount-1;
end WHILE;

while current>0 do
set pageNumber=current-1;
set strValue = (select personal_id from personal_contact group by personal_id limit pageNumber,1);
set countNum =(select count(*) from personal_contact where personal_id =strValue);
set firstNumber=countNum;
if countNum=1 then
insert into personal_contact_temp(id,personal_id,relation,name,phone,phone_status,mobile)
(select uuid(),personal_id,relation,`name`,phone,phone_status,mobile from personal_contact where personal_id =strValue);
ELSE
while countNum>0 do
set pageNumber=countNum-1;
if(firstNumber=countNum) then
insert into personal_contact_temp(id,personal_id,relation,name,phone,phone_status,mobile)
(select uuid(),personal_id,relation,`name`,phone,phone_status,mobile from personal_contact where personal_id =strValue LIMIT pageNumber,1);
ELSE
BEGIN
set sqlValue='';
set sqlValue= CONCAT('update personal_contact_temp a left join
(select relation,`name`,phone,phone_status,mobile,personal_id from personal_contact where personal_id =',"'",strValue,"'",' limit ',pageNumber,',1) b
on a.personal_id =b.personal_id
set a.relation',countNum,'A','=b.relation,
a.name',countNum,'A','=b.`name`,
a.phone',countNum,'A','=b.phone,
a.phone_status',countNum,'A','=b.phone_status,
a.mobile',countNum,'A','=b.mobile where a.personal_id =',"'",strValue,"'",';');
set @ms=sqlValue;
PREPARE stmt1 FROM @ms;
EXECUTE stmt1;
end;
end if;
set countNum =countNum-1;
end WHILE;
end if;
set current=current-1;
end WHILE;
END;

注意 这个存储过程在运行的时候回报 列太大的问题，就是如果多行数据展示到一行，会超出 mysql 行数据的最大值。 这个可以酌情处理。

方法2. Mysql 提供了 group_concat 函数

select GROUP_CONCAT(`name`,'"',',',relation,'"',',',phone) from personal_contact GROUP BY personal_id;

通过这个函数可以将你要查询的数据放到一个列中，然后到处CSV格式的数据，将后面这一列的数据转化成CSV格式的数据，然后存成CSV导入到数据库中。

欢迎大家提出更多解决方案。