sql取每个分组的第一行数据

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');