行转列、列转行

一：行转列


模式：N行转一列  本实验N取3
1.建表
SQL> create table grade(id int,name varchar2(10),subject varchar2(10),grade number(3));
2.插入实验数据
insert into grade values(1,'Andy','Yuwen',11);
insert into grade values(2,'Andy','Math',22);
insert into grade values(3,'Andy','English',33);
insert into grade values(4,'Zhang','English',44);
insert into grade values(5,'Zhang','Math',55);
insert into grade values(6,'Zhang','Yuwen',66);
insert into grade values(7,'Tao','Yuwen',77);
insert into grade values(8,'Tao','Math',88);
commit;
3.查询
SQL> select * from grade;


        ID NAME       SUBJECT         GRADE
---------- ---------- ---------- ----------
         1 Andy       Yuwen              11
         2 Andy       Math               22
         3 Andy       English            33
         4 Zhang      English            44
         5 Zhang      Math               55
         6 Zhang      Yuwen              66
         7 Tao        Yuwen              77
         8 Tao        Math               88
8 rows selected.
4.错误示范，缺失 sum 。
SQL>  
select name,
decode(subject,'Yuwen', grade,null) "Language",
decode(subject,'Math', grade,null) "Math",
decode(subject,'English', grade,null) "English"
from grade;


NAME         Language       Math    English
---------- ---------- ---------- ----------
Andy               11
Andy                          22
Andy                                     33
Zhang                                    44
Zhang                         55
Zhang              66
Tao                77
Tao                           88


4. 转换。正确示范
方法一：
SQL> 
select name,
sum(decode(subject,'Yuwen', grade,0)) "Yuwen",
sum(decode(subject,'Math', grade,0)) "Math",
sum(decode(subject,'English', grade,0)) "English"
from grade
group by name;


NAME            Yuwen       Math    English
---------- ---------- ---------- ----------
Zhang              66         55         44
Andy               11         22         33
Tao                77         88          0
方法二：
SELECT name,
SUM(CASE WHEN subject='Yuwen' THEN grade ELSE 0 END) AS "Yuwen",
SUM(CASE WHEN subject='Math' THEN grade ELSE 0 END) AS "Math",
SUM(CASE WHEN subject='English' THEN grade ELSE 0 END) AS "English"
FROM grade
group by name;


二、列转行


模式：一列转N行，本实验N取3 （说明：相同类型数据确定N的取值，比如：YUWEN，MATH，ENGLISH 所以取3）
1.建表
create table score(id int,name varchar2(10),Yuwen number(3),Math number(3),English number(3));
2.插入数据
insert into score values(1,'Zhang',11,22,33);
insert into score values(2,'Andy',44,55,66);
insert into score(id,name,Yuwen) values(3,'Tao',77);
commit;
3.查询
SQL> select * from score;


        ID NAME            YUWEN       MATH    ENGLISH
---------- ---------- ---------- ---------- ----------
         1 Zhang              11         22         33
         2 Andy               44         55         66
         3 Tao                77
4.转换
SELECT name, 'Yuwen' subject,Yuwen grade FROM score
UNION ALL
SELECT name, 'Math' subject,Math grade FROM score
UNION ALL
SELECT name, 'English' subject,English grade FROM score
order by name;


NAME       SUBJECT      GRADE
---------- ------- ----------
Andy       Math            55
Andy       English         66
Andy       Yuwen           44
Tao        English
Tao        Math
Tao        Yuwen           77
Zhang      Math            22
Zhang      English         33
Zhang      Yuwen           11
9 rows selected.
注意：加引号表示是字符串，不加引号取列的值
模式：N列转成一行
1.建表
create table test(dname varchar2(10),ename varchar2(10));
2.插入数据
insert into test values('Guowang','Andy');
insert into test values('Guowang','Zhang');
insert into test values('Guowang','Chong');
insert into test values('Nvwang','Tao');
insert into test values('Nvwang','Ye');
insert into test values('happy','Leaf');
commit;
3.查询
SQL> select * from test;


DNAME      ENAME
---------- ----------
Guowang    Andy
Guowang    Zhang
Guowang    Chong
Nvwang     Tao
Nvwang     Ye
happy      Leaf
6 rows selected.
目标转换模式：
DNAME      NAME
---------- ----------------
Guowang    Andy,Zhang,Chong
Nvwang     Tao,Ye
happy      Leaf
4. 转换
方法一：
-- 一种简单通过函数的方法，有oracle版本限制，作为一种备选方案。
SQL> col name for a40
SQL> select dname,WMSYS.WM_CONCAT(ename) NAME from test group by dname;


DNAME      NAME
---------- ----------------------------------------
Guowang    Andy,Chong,Zhang
Nvwang     Tao,Ye
happy      Leaf
方法二：
构造出来一个层次，利用层次查询处理
4.2.1 -- 虚构员工编号
SQL> SELECT dname, ename, ROW_NUMBER() OVER (ORDER BY dname) rn FROM test;


DNAME      ENAME              RN
---------- ---------- ----------
Guowang    Andy                1
Guowang    Zhang               2
Guowang    Chong               3
Nvwang     Tao                 4
Nvwang     Ye                  5
happy      Leaf                6
4.2.2-- 领导编号
SELECT dname, ename, rn, LEAD (rn) OVER (PARTITION BY dname ORDER BY rn) rn1
FROM (SELECT dname, ename, ROW_NUMBER () OVER (ORDER BY dname) rn FROM test);
DNAME      ENAME              RN        RN1
---------- ---------- ---------- ----------
Guowang    Andy                1          2
Guowang    Zhang               2          3
Guowang    Chong               3
Nvwang     Tao                 4          5
Nvwang     Ye                  5
happy      Leaf                6
4.2.3 转换
col name for a40;
SELECT dname, SUBSTR(MAX (SYS_CONNECT_BY_PATH (ename, ',')), 2) NAME
FROM (
SELECT dname, ename, rn, LEAD (rn) OVER (PARTITION BY dname ORDER BY rn) rn1
FROM (SELECT dname, ename, ROW_NUMBER () OVER (ORDER BY ename) rn
FROM test)
)
START WITH rn1 IS NULL
CONNECT BY rn1 = PRIOR rn
GROUP BY dname;


DNAME      NAME
---------- -----------------------------
happy      Leaf
Nvwang     Ye,Tao
Guowang    Zhang,Chong,Andy