Oracle 行转列、列转行 的Sql语句总结

select concat(id,username) str from app_user select id||username str from app_user

create table test(id number,name varchar2(20)); insert into test values(1,'a'); insert into test values(1,'b'); insert into test values(1,'c'); insert into test values(2,'d'); insert into test values(2,'e');

效果1 :   行转列  ，默认逗号隔开

select wm_concat(name) name from test;

效果2:   把结果里的逗号替换成"|"

select replace(wm_concat(name),',','|') from test;

效果3:  按ID分组合并name

select id,wm_concat(name) name from test group by id;

sql语句等同于下面的sql语句

-------- 适用范围：8i,9i,10g及以后版本  （ MAX + DEcode ）
select id, max(decode(rn, 1, name, null)) || max(decode(rn, 2, ',' || name, null)) || max(decode(rn, 3, ',' || name, null)) str
       from (select id,name,row_number() over(partition by id order by name) as rn from test) t group by id order by 1; 
     
-------- 适用范围：8i,9i,10g及以后版本 （ ROW_NUMBER + LEAD ）
select id, str from (select id,row_number() over(partition by id order by name) as rn,name || lead(',' || name, 1) over(partition by id order by name) ||
       lead(',' || name, 2) over(partition by id order by name) || lead(',' || name, 3) over(partition by id order by name) as str from test) where rn = 1 order by 1;
  

-------- 适用范围：10g及以后版本 （ MODEL ）
select id, substr(str, 2) str from test model return updated rows partition by(id) dimension by(row_number() over(partition by id order by name) as rn) 
measures (cast(name as varchar2(20)) as str) rules upsert iterate(3) until(presentv(str[iteration_number+2],1,0)=0) (str[0] = str[0] || ',' || str[iteration_number+1]) order by 1;     
         
-------- 适用范围：8i,9i,10g及以后版本 （ MAX + DEcode ）
select t.id id,max(substr(sys_connect_by_path(t.name,','),2)) str from (select id, name, row_number() over(partition by id order by name) rn from test) t
       start with rn = 1 connect by rn = prior rn + 1 and id = prior id group by t.id;</span>

懒人扩展用法:

案例: 我要写一个视图,类似"create or replace view as select 字段1,...字段50 from tablename" ,基表有50多个字段,要是靠手工写太麻烦了,有没有什么简便的方法? 当然有了,看我如果应用wm_concat来让这个需求变简单，假设我的APP_USER表中有（id,username,password,age）4个字段。查询结果如下

 /** 这里的表名默认区分大小写 */
 select 'create or replace view as select '|| wm_concat(column_name) || ' from APP_USER' sqlStr from user_tab_columns where table_name='APP_USER';

利用系统表方式查询

select * from user_tab_columns

在Oracle 11g中，Oracle 又增加了2个查询：pivot（行转列） 和unpivot（列转行）

参考：http://blog.csdn.net/tianlesoftware/article/details/7060306、http://www.oracle.com/technetwork/cn/articles/11g-pivot-101924-zhs.html

google 一下，网上有一篇比较详细的文档：

pivot 列转行

测试数据 (id，类型名称，销售数量)，案例：根据水果的类型查询出一条数据显示出每种类型的销售数量。

create table demo(id int,name varchar(20),nums int);  ---- 创建表
insert into demo values(1, '苹果', 1000);
insert into demo values(2, '苹果', 2000);
insert into demo values(3, '苹果', 4000);
insert into demo values(4, '橘子', 5000);
insert into demo values(5, '橘子', 3000);
insert into demo values(6, '葡萄', 3500);
insert into demo values(7, '芒果', 4200);
insert into demo values(8, '芒果', 5500);

分组查询 （当然这是不符合查询一条数据的要求的）

select name, sum(nums) nums from demo group by name

行转列查询

select * from (select name, nums from demo) pivot (sum(nums) for name in ('苹果' 苹果, '橘子', '葡萄', '芒果'));

注意： pivot（聚合函数 for 列名 in（类型））   ，其中 in(‘’) 中可以指定别名

当然也可以不使用pivot函数，等同于下列语句，只是代码比较长，容易理解

select * from （select sum(nums) 苹果 from demo where name='苹果'）,（select sum(nums) 橘子 from demo where name='橘子'）,
       （select sum(nums) 葡萄 from demo where name='葡萄'）,（select sum(nums) 芒果 from demo where name='芒果'） ;
       

create table Fruit(id int,name varchar(20), Q1 int, Q2 int, Q3 int, Q4 int); insert into Fruit values(1,'苹果',1000,2000,3300,5000); insert into Fruit values(2,'橘子',3000,3000,3200,1500); insert into Fruit values(3,'香蕉',2500,3500,2200,2500); insert into Fruit values(4,'葡萄',1500,2500,1200,3500); select * from Fruit

列转行查询

select id , name, jidu, xiaoshou from Fruit unpivot (xiaoshou for jidu in (q1, q2, q3, q4) )

注意：  unpivot没有聚合函数，xiaoshou、jidu字段也是临时的变量

同样不使用unpivot也可以实现同样的效果，只是sql语句会很长，而且执行速度效率也没有前者高

select id, name ,'Q1' jidu, (select q1 from fruit where id=f.id) xiaoshou from Fruit f
union
select id, name ,'Q2' jidu, (select q2 from fruit where id=f.id) xiaoshou from Fruit f
union
select id, name ,'Q3' jidu, (select q3 from fruit where id=f.id) xiaoshou from Fruit f
union
select id, name ,'Q4' jidu, (select q4 from fruit where id=f.id) xiaoshou from Fruit f

XML类型

上述pivot列转行示例中，你已经知道了需要查询的类型有哪些，用in()的方式包含，假设如果您不知道都有哪些值，您怎么构建查询呢？