Question

我想创建一个表，列出表中每条记录与特定列的每条记录的比较：

示例：

id | web        | author | book        | isbn   | pub 
----------------------------------------------------------------
1  | www.a.com  |  sam  |  sams book   | 12345  |  sams pub
2  | www.b.com  |  ram  |  rams book   | 54321  |  rams pub
3  | www.c.com  |  sam  |  rams book   | 67891  |  tams pub
4  | www.b.com  |  ram  |  gams book   | 65644  |  gams pub
5  | www.a.com  |  sam  |  sams book   | 11111  |  xyzs pub
6  | www.c.com  |  tam  |  tams book   | 22222  |  abcs pub
7  | www.c.com  |  tam  |  tams book   | 33333  |  pqrs pub

所以我想创建一个表，其中包含每条记录与其他记录的比较结果在列网站，作者，书

结果表应该是:(结果权重是网络+作者+书籍权重的加法）

sorceRow|destRow| web   | author | book |  result weight
--------------------------------------------------------
 1     |   2    |    0  | 0      | 0    |      0
 1     |   3    |    0  | 1      | 0    |      1 
 1     |   4    |    0  | 0      | 0    |      0
 1     |   5    |    1  | 1      | 1    |      3
 1     |   6    |    0  | 0      | 0    |      0
 1     |   7    |    0  | 0      | 0    |      0
 2     |   3    |    0  | 0      | 1    |      1
 2     |   4    |    1  | 1      | 0    |      2
 2     |   5    |    0  | 0      | 0    |      0
 2     |   6    |    0  | 0      | 0    |      0
 ...
 6     |   7    |  1    | 1      | 1    |      3

在SQL Server脚本和C＃中获得此结果的最快方法是什么？

Answer 1

你可以使用非等值和许多比较来做到这一点。以下是标准的SQL方法：

select t1.id as sourceRow, t2.id as destRow,
       (case when t1.web = t2.web then 1 else 0 end) as Web,
       (case when t1.Author = t2.Author then 1 else 0 end) as Author,
       (case when t1.Book = t2.Book then 1 else 0 end) as Book,
       (case when t1.ISBN = t2.ISBN then 1 else 0 end) as ISBN,
       (case when t1.pub = t2.pub then 1 else 0 end) as pub
from table t1 join
     table t2
     on t1.id < t2.id;

请注意，如果列可能包含NULL值，则比较会稍微复杂一些，但您的示例数据却没有。

Answer 2

基本上表格的CROSS JOIN本身就会进行乘法运算Cross Join。至于比较，它取决于你使用的数据库服务器 - case或iif（）。

select
    l.id as sourceRow,
    r.id as destRow,
    iif (r.web = l.web, 1, 0) as web,
    iif (r.author = l.author, 1, 0) as author,
    ....
from T1 l
cross join T1 r
where l.id < r.id

表列出了其他表中每条记录的比较

2 个答案: