Question

我已将一个列（seq）添加到用于计划的表中，因此前端可以管理每个项目的显示顺序。是否可以使用基于日期列中的公共重复值的增量计数器来创建SQL查询来填充此列？

在

------------------------------------
| name | date_time           | seq |
------------------------------------
| ABC1 | 15-01-2017 11:00:00 |     |
| ABC2 | 16-01-2017 11:30:00 |     |
| ABC1 | 16-01-2017 11:30:00 |     |
| ABC3 | 17-01-2017 10:00:00 |     |
| ABC3 | 18-01-2017 12:30:00 |     |
| ABC4 | 18-01-2017 12:30:00 |     |
| ABC1 | 18-01-2017 12:30:00 |     |
------------------------------------

在

------------------------------------
| name | date_time           | seq |
------------------------------------
| ABC1 | 15-01-2017 11:00:00 | 0   |
| ABC2 | 16-01-2017 11:30:00 | 0   |
| ABC1 | 16-01-2017 11:30:00 | 1   |
| ABC3 | 17-01-2017 10:00:00 | 0   |
| ABC3 | 18-01-2017 12:30:00 | 0   |
| ABC4 | 18-01-2017 12:30:00 | 1   |
| ABC1 | 18-01-2017 12:30:00 | 2   |
------------------------------------

解决了，感谢两个答案。为了让任何找到这个的人更容易，工作代码是：

UPDATE my_table f
    SET seq = seq2
    FROM (
        SELECT ctid, ROW_NUMBER() OVER (PARTITION BY date_time ORDER BY ctid) -1 AS seq2
        FROM my_table
        ) s
    WHERE f.ctid = s.ctid;

Answer 1

查看ROW_NUMBER()。

import {Router, ActivatedRoute, Params} from '@angular/router';
import {OnInit, Component} from '@angular/core';
import {ArticlesService} from "./articles.service";
import {Article} from "./article.model";

@Component({...})
export class ArticleComponent implements OnInit {
  article: Article;
  constructor(private activatedRoute: ActivatedRoute) {}

  ngOnInit() {
    this.activatedRoute.params.subscribe((params: Params) => {
        let id = params['id'];
           this.articleService.findArticle(id).subscribe(
               (article: Article) => this.article = article;
           );
      });
  }

}

Answer 2

使用window function row_number()：

with my_table (name, date_time) as (
values

('ABC1', '15-01-2017 11:00:00'),
('ABC2', '16-01-2017 11:30:00'),
('ABC1', '16-01-2017 11:30:00'),
('ABC3', '17-01-2017 10:00:00'),
('ABC3', '18-01-2017 12:30:00'),
('ABC4', '18-01-2017 12:30:00'),
('ABC1', '18-01-2017 12:30:00')
)

select *, 
    row_number() over (partition by name order by date_time)- 1 as seq
from my_table
order by date_time;

 name |      date_time      | seq 
------+---------------------+-----
 ABC1 | 15-01-2017 11:00:00 |   0
 ABC1 | 16-01-2017 11:30:00 |   1
 ABC2 | 16-01-2017 11:30:00 |   0
 ABC3 | 17-01-2017 10:00:00 |   0
 ABC1 | 18-01-2017 12:30:00 |   2
 ABC3 | 18-01-2017 12:30:00 |   1
 ABC4 | 18-01-2017 12:30:00 |   0
(7 rows)

关于使用唯一整数更新现有记录的类似问题，请阅读this answer。

Postgresql - 在列具有重复值

2 个答案: