SELECT NAME, MAX(CASE WHEN COURSE='语文' THEN  SCORE END) "语文", MAX(CASE WHEN COURSE='数学' THEN  SCORE END) "数学", MAX(CASE WHEN COURSE='英语' THEN  SCORE END) "英语", MAX(CASE WHEN COURSE='物理' THEN  SCORE END) "物理", SUM(SCORE) "总分"
FROM stu GROUP BY NAME;

SELECT NAME, CASE WHEN LV = 1 THEN  '语文' --常量 WHEN LV = 2 THEN  '数学' --常量 WHEN LV = 3 THEN  '英语' --常量 WHEN LV = 4 THEN  '物理' --常量 END 科目, CASE WHEN LV = 1 THEN langu --列名 WHEN LV = 2 THEN math--列名 WHEN LV = 3 THEN english--列名 WHEN LV = 4 THEN pycial--列名 END 成绩
FROM (  SELECT * FROM course, (SELECT LEVEL LV FROM DUAL CONNECT BY LEVEL <= 4)  ) --成绩对应的列数
ORDER BY 1, 2; 

--查询每个部门的人数
SELECT DEPTNO, COUNT(1) CN FROM EMP GROUP BY DEPTNO ORDER BY 1; 

--将上面的结果转为一行,可以使用 SUM 或者 COUNT 来求出。
SELECT SUM(CASE WHEN DEPTNO = 10 THEN 1 END) D_10, SUM(CASE WHEN DEPTNO = 20 THEN 1 END) D_20, SUM(CASE WHEN DEPTNO = 30 THEN 1 END) D_30 FROM EMP;
--也可以使用下面的方法。
SELECT CASE WHEN DEPTNO = 10 THEN CN END D_10, CASE WHEN DEPTNO = 20 THEN CN END D_20, CASE WHEN DEPTNO = 30 THEN CN END D_30 FROM (SELECT DEPTNO, COUNT(1) CN FROM EMP GROUP BY DEPTNO);
--和刚讲的一样，生成了三行三列数据，使用 MAX 来获取。
SELECT MAX(CASE WHEN DEPTNO = 10 THEN CN END) D_10, MAX(CASE WHEN DEPTNO = 20 THEN CN END) D_20, MAX(CASE WHEN DEPTNO = 30 THEN CN END) D_30 FROM (SELECT DEPTNO, COUNT(1) CN FROM EMP GROUP BY DEPTNO); 

SELECT MAX(CASE JOB WHEN 'CLERK' THEN ENAME END) CLERK, MAX(CASE JOB WHEN 'ANALYST' THEN ENAME END) ANALYST,      MAX(CASE JOB WHEN 'MANAGER' THEN ENAME END) MANAGER, MAX(CASE JOB WHEN 'PRESIDENT' THEN ENAME END) PRESIDENT, MAX(CASE JOB WHEN 'SALESMAN' THEN ENAME END) SALESMAN FROM (SELECT ENAME, JOB, --每组都是从 1 开始排序,而每列里面只有一组有数据。也就是 RN 相同的在每列里面只有一条数据ROW_NUMBER() OVER(PARTITION BY JOB ORDER BY ENAME) RN FROM EMP)
GROUP BY RN
ORDER BY RN;