取分组（group by）记录的第一条
1 --建立测试环境
CREATE TABLE table1(a VARCHAR(10),b VARCHAR(10),c VARCHAR(10));
--插入数据
INSERT INTO table1 VALUES('2004','12','storea');
INSERT INTO table1 VALUES('2005','07','storea');
INSERT INTO table1 VALUES('2004','11','storeb');
INSERT INTO table1 VALUES('2005','06','storeb');
COMMIT;
2 取分组记录的第一条
解法一
SELECT a.* FROM table1 a INNER JOIN (
SELECT MAX(a + b)TIME FROM table1
GROUP BY c ) b
ON a.a + a.b = b.TIME
解法二
SELECT * FROM scott.table1 a WHERE NOT EXISTS
(SELECT 1 FROM scott.table1 b WHERE a.a=b.a AND TO_NUMBER(a.b)<TO_NUMBER(b.b));
解法三
SELECT * FROM (SELECT t.*, RANK()
OVER (PARTITION BY t.a ORDER BY t.b DESC) AS drank
FROM table1 t) a WHERE drank=1
引申
SELECT t.*,SUM(b) OVER (PARTITION BY t.a) AS aaa,
SUM(b) OVER () AS bbb
FROM table1 t
ORDER BY t.a,t.b
－－－－－－
SELECT d.department_id , e.last_name, e.salary, RANK()
OVER (PARTITION BY e.department_id ORDER BY e.salary) AS drank
FROM employees e, departments d
WHERE e.department_id = d.department_id
AND d.department_id IN ('60', '90');
