更改所有行的列值

Question

我有以下表格：

create table dbo.Files (
  Id int identity not null constraint PK_Files_Id primary key (Id),
  Content varbinary (max) null,
  Name nvarchar (280) null
)

create table dbo.BookFiles (
  BookId int not null, 
  FileId int not null, 
    constraint PK_BookFiles_Id primary key (BookId, FileId)
)

alter table dbo.BookFiles
add constraint FK_BookFiles_BookId foreign key (BookId) references Books(Id) on delete cascade on update cascade,
    constraint FK_BookFiles_FileId foreign key (FileId) references Files(Id) on delete cascade on update cascade;

一些数据如下：

BookId    FileId    Id   Name    Content
1         1         1    image
1         2         1    image
2         3         2    image
3         4         3    image

有些书有2张图片（BookdId = 1），有些有1张图片（BookId = 2,3）。

我需要将所有文件的名称重命名为：

1. “image1”为本书的第一张图片（最低的FileId）;
2. 如果存在，书的第二个图像的“image2”。

我知道如何更新所有行中的值：

UPDATE files SET name = "image1";  

但我不知道如何设置“image1”和“image2”如上所述。

有人可以帮助我吗？

Answer 1

使用子查询过滤掉具有多个图像的书籍

update t set t.name = case when fileid = 1 then 'ima1' else 'ima2' end 
from table t
where bookid in (
    select bookid from table
    group by bookid
    having  count(*) > 1
)

为了更新所有文件图像，您可以使用排名功能row_number()

with cte as
(
   select *, 
          row_number() over  (partition by b.BookId order by b.FileId) Seq 
   from BookFiles b
   inner join Files f ON f.Id = b.FileId
)
update cte set name = concat(name, Seq) 

Answer 2

从您的问题中获取数据，下面的代码片段可以根据您的需要为您提供结果 -

declare @t table (BookId int,    FileId int,    Id int,   Name  nvarchar(280),   Content varbinary (max))
insert into @t values
(1,         1,         1,    'image',null),
(1,         2,         1,    'image',null),
(2,         3,         2,    'image',null),
(3,         4,         3,    'image',null)
;with cte as
(
select *, ROW_NUMBER() OVER(PARTITION BY BookId ORDER BY BookId) rn
from @t
)
select BookId,FileId,Id,(Name+cast(rn as nvarchar(1))) AS Name,Content from cte

Answer 3

你可以试试CTE。它不仅仅适用于具有相同ID的2个图像，它适用于您对书籍的任意数量的图像，该数字将相应地附加。

    ;WITH CT AS
    (
      SELECT BOOKID, FILEID, ROW_NUMBER() OVER 
        (PARTITION BY BookId ORDER BY BOOKID) AS RN , NAME 
       FROM BookFiles BF INNER JOIN Files F ON F.Id = BF.FileId
    )
    UPDATE CT
    SET NAME= 'image' + CAST(RN AS VARCHAR(10))

注意：您对CTE所做的更新将级联到源表。