row_number() OVER (PARTITION BY COL1 ORDER BY COL2)「建议收藏」

大家好，又见面了，我是全栈君。

row_number() OVER (PARTITION BY COL1 ORDER BY COL2) –表示依据COL1分组，在分组内部依据 COL2排序。而此函数返回的值就表示每组内部排序后的顺序编号（组内连续的唯一的)

create table student (id int ,classes int ,score int);
insert into student values(1,1,89);
insert into student values(2,1,90);
insert into student values(3,1,76);
insert into student values(4,2,69);
insert into student values(5,2,79);
insert into student values(6,2,95);
insert into student values(7,3,80);
insert into student values(8,3,85);
insert into student values(9,3,79);
commit;

select t.* from student t;

–数据显示为 id classes score ————————————————————- 1 1 89 2 1 90 3 1 76 4 2 69 5 2 79 6 2 95 7 3 80 8 3 85 9 3 79

–需求：依据班级分组，显示每一个班的英语成绩排名

–预期结果：

id classes score rank ———– ———– ————————————— 3 1 76 1 1 1 89 2 2 1 90 3 4 2 69 1 5 2 79 2 6 2 95 3 9 3 79 1 7 3 80 2 8 3 85 3

–SQL脚本：

SELECT *, Row_Number() OVER (partition by classes ORDER BY score desc) rank FROM student;

–查询t_test表中，callid字段没有反复过的数据，效率高过group by having count

select t.*, t.rowid
  from t_test t
 where t.rowid not in (select rid
                         from (select t2.rowid rid,
                                      row_number() over(partition by t2.callid order by t2.rowid desc) m
                                 from t_test t2)
                        where m <> 1)
   and t.rowid not in (select rid
                         from (select t2.rowid rid,
                                      row_number() over(partition by t2.callid order by t2.rowid asc) m
                                 from t_test t2)
                        where m <> 1);

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