Oracle中的行转列例子详解

--场景1：
A　　B
a　　1
a　　2
a　　3
b　　4
b　　5

希望实现如下效果：
a  1,2,3
b  4,5

create table tmp as
select 'a' A, 1 B from dual union all
select 'a' A, 2 B from dual union all
select 'a' A, 3 B from dual union all
select 'b' A, 4 B from dual union all
select 'b' A, 5 B from dual;

1.方法1：listagg
--listagg() + group by: 推荐使用
select a,listagg(b,',')  within group (order by b) as c from tmp group by a;
--listagg() + over(partition by )
select distinct a,listagg(b,',')  within group (order by b) over(partition by a) as c from tmp ;

2.wm_concat
select a,to_char(wm_concat(b)) as b from tmp group by a

3.sys_connect_by_path
select a, max(substr(sys_connect_by_path(b, ','), 2)) str
  from (select a, b, row_number() over(partition by a order by b) rn from tmp)
 start with rn = 1
connect by rn = prior rn + 1
    and a = prior a
  group by a;

4.max+decode
select a,
       max(decode(rn, 1, b, null)) ||
       max(decode(rn, 2, ',' || b, null)) ||
       max(decode(rn, 3, ',' || b, null)) str
  from (select a,b,row_number() over(partition by a order by b) as rn from tmp)
 group by a
 order by 1;

5.row_number()+lead
select a, str b
  from (select a,
               row_number() over(partition by a order by b) as rn,
               b || lead(',' || b, 1) over(partition by a order by b) ||
               lead(',' || b, 2) over(partition by a order by b) ||
               lead(',' || b, 3) over(partition by a order by b) as str
          from tmp
)
 where rn = 1
 order by 1;

6.model语句
select a, substr(str,2) b
  from tmp
  model return updated rows partition by(a) dimension by(row_number()  over(partition by a order by b) as rn)
  measures(cast(b as varchar2(20)) as str)
  rules upsert iterate(3) until(presentv(str[iteration_number+2],1,0) = 0)
  (str[] = str[]||','||str[iteration_number + 1])
 order by 1;

--场景2：
no  sex
004 2
002 2
002 2
003 1
002 1 

希望实现如下效果：
      c1   c2
002   1    2
003   1    0
004   0    1 

也就是说按no sex两个字段count人数，得到二维表。

--1.添加测试数据
create table tt(no varchar(20 char), sex number);
insert into tt values('',2);
insert into tt values('',2);
insert into tt values('',2);
insert into tt values('',1);
insert into tt values('',1);
commit;
select * from tt;

--2.SQL实现
--存储过程动态拼接
--(1)使用case
create or replace procedure row_to_line
is
    str_sql varchar2(4000);
begin
    str_sql := ' create or replace view v_row_to_line as select no ';

    for x in (select distinct sex from tt) loop
        str_sql := str_sql || ',count(case when sex = '||x.sex||' then 1 else null end ) "'||x.sex||'"';
    end loop;

    str_sql := str_sql || ' from tt group by no order by no ';

    execute immediate str_sql;

end;
/

--(2)使用decode
create or replace procedure row_to_line
is
    str_sql varchar2(4000);
begin
    str_sql := ' create or replace view v_row_to_line as select no ';

    for x in (select distinct sex from tt) loop
        str_sql := str_sql || ',count(decode(sex, '||x.sex||', 1 , null)) "'||x.sex||'"';
    end loop;

    str_sql := str_sql || ' from tt group by no order by no ';

    execute immediate str_sql;

end;
/

SQL> exec row_to_line;

PL/SQL procedure successfully completed

SQL> select * from v_row_to_line;

NO                                                1          2
---------------------------------------- ---------- ----------
002                                               1          2
003                                               1          0
004                                               0          1

--(3)动态传表名+列名
create or replace procedure row_to_line
(
   str_tabname   in  varchar2,
   str_col1      in  varchar2,
   i_col2        in  varchar2
)
is
    str_sql varchar2(4000);
begin
    str_sql := ' create or replace view v_row_to_line as select '||str_col1||' ';

    for x in (select distinct sex from tt ) loop
        str_sql := str_sql || ',count(decode('||i_col2||', '||x.sex||', 1, null)) "'||x.sex||'"';
    end loop;

    str_sql := str_sql || ' from '||str_tabname||' group by '||str_col1||' order by '||str_col1||' ';

    execute immediate str_sql;

end;

--(4)使用游标
create or replace procedure row_to_line
(
   str_tabname   in  varchar2,
   str_col1      in  varchar2,
   i_col2        in  varchar2,
   cur_result    out sys_refcursor
)
is
    str_sql varchar2(4000);
begin
    str_sql := 'select '||str_col1||' ';

    for x in (select distinct sex from tt ) loop
        str_sql := str_sql || ',count(decode('||i_col2||', '||x.sex||', 1, null)) "'||x.sex||'"';
    end loop;

    str_sql := str_sql || ' from '||str_tabname||' group by '||str_col1||' order by '||str_col1||' ';

    open cur_result for str_sql;

end;

--(5).使用sql语句也可以解决
select no,
       count(case sex when 1 then 1 else null end) c1,
       count(case sex when 2 then 1 else null end) c2
  from tt
 group by no
 order by no;