Question

在SQL中是否有办法按密钥组依次添加行号？

假设一个具有任意（CODE，NAME）元组的表。示例表：

CODE NAME ---- ---- A Apple A Angel A Arizona B Bravo C Charlie C Cat D Dog D Doppler D Data D Down

使用CODE作为分组属性的预期投影：

CODE C_NO NAME ---- ---- ---- A 0 Apple A 1 Angel A 2 Arizona B 0 Bravo C 1 Charlie C 0 Cat D 0 Dog D 1 Data D 2 Down D 3 Doppler

谢谢，

Answer 1

MySQL没有AFAIK。这涵盖了大多数基地..

SELECT
    CODE,
    ROW_NUMBER() OVER (PARTITION BY CODE ORDER BY NAME) - 1 As C_NO,
    NAME
FROM
    MyTable

Answer 2

MySQL（可能还有大多数其他数据库）：

select g.CODE
     , count(*)-1 as C_NO
     , g.NAME
from MyTable as g
  left join MyTable as o
    on g.CODE = o.CODE
      and g.NAME >= o.NAME
group by g.CODE
       , g.NAME;

特定于MySQL：

DELIMITER $$
CREATE PROCEDURE NumberRowsByGroup()
BEGIN
  SET  @code := 0;
  SET  @num := 0;
  SELECT CODE, C_NO, NAME FROM
    ( select q.CODE
           , q.NAME
           , @num := IF(q.CODE = @code, @num + 1, 0) as C_NO
           , @code := q.CODE as previous
      from yourTable q
      order by CODE
             , NAME
    ) as p
  ;
END$$
DELIMITER ;

然后，我们可以致电：

CALL NumberRowsByGroup();

根据xaprb.com/blog帖子：how-to-number-rows-in-mysql，第二个更快。

在SQL中按键键组顺序编号行？

2 个答案: