好了，現在我們就可以在查詢句法中直接關聯表了（資料庫中不一定要設定表的外來鍵關
系）：
response.write(
"-------------
查詢分類為
1 的版塊
-------------");
varquery1 =
from
b in
ctx.boards
where
b.category.categoryid == 1
selectb;
foreach
(board
b in
query1)
response.write(b.boardid +
" "+ b.boardname + ""
); response.write(
"-------------
查詢版塊大於
2 個的分類
-------------");
varquery2 =
from
c in
ctx.boardcategories
where
c.boards.count > 2
select
c;
foreach
(boardcategory
c in
query2)
response.write(c.categoryid +
" "+ c.categoryname+
" "+
c.boards.count + ""
); 在資料庫中加一些測試資料，
便我不需要再用語言形容了吧。執行上述的程式會導致下面
sql
的執行：
select [t0].[boardid], [t0].[boardname],[t0].[boardcategory]
from [boards] as [t0]
inner join [categories] as [t1] on[t1].[categoryid] = [t0].[boardcategory]
where [t1].[categoryid] = @p0
-- @p0: input int32 (size = 0; prec = 0;scale = 0) [1]
select [t0].[categoryid],[t0].[categoryname]
from [categories] as [t0]
where ((
select count(*)
from [boards] as [t1]
where [t1].[boardcategory] = [t0].[categoryid]
)) > @p0
-- @p0: input int32 (size = 0; prec = 0; scale= 0) [2]
select [t0].[boardid], [t0].[boardname],[t0].[boardcategory]
from [boards] as [t0]
where [t0].[boardcategory] = @p0
-- @p0: input int32 (size = 0; prec = 0;scale = 0) [1]
可以看到，第二個查詢並沒有做外連線，還記得
dataloadoptions
嗎？我們可以要求
linq to sql
在讀取版塊分類資訊的時候也把版塊資訊一起載入：
dataloadoptions
options =
new
dataloadoptions
();
options.loadwith<
boardcategory
>(c => c.boards);
ctx.loadoptions = options;
response.write(
"-------------
查詢版塊大於
2 個的分類
-------------");
varquery2 =
from
c in
ctx.boardcategories
where
c.boards.count > 2
select
c;
foreach
(boardcategory
c in
query2)
response.write(c.categoryid +
" "+ c.categoryname+
" "+
c.boards.count + ""
); 查詢經過改造後會得到下面的
sql：
select [t0].[categoryid],[t0].[categoryname], [t1].[boardid], [t1].[boardname],
[t1].[boardcategory], (
select count(*)
from [boards] as [t3]
where [t3].[boardcategory] = [t0].[categoryid]
)as [count]
from [categories] as [t0]
left outer join [boards] as [t1] on[t1].[boardcategory] = [t0].[categoryid]
where ((
select count(*)
from [boards] as [t2]
where [t2].[boardcategory] = [t0].[categoryid]
)) > @p0
order by [t0].[categoryid], [t1].[boardid]
-- @p0: input int32 (size = 0; prec = 0;scale = 0) [2]
在新增分類的時候，如果這個分類下還有新的版塊，那麼提交新增分類的時候版塊也
會新增：
boardcategory
dbcat =
new
boardcategory
() ;
board
oracle =
new
board
() ;
ctx.boardcategories.add(dbcat);
ctx.submitchanges();
上述**導致下面的
sql
被執行：
insert into [categories]([categoryname])values (@p0)
select [t0].[categoryid]
from [categories] as [t0]
where [t0].[categoryid] =(scope_identity())
-- @p0: input ansistring (size = 8; prec =0; scale = 0) [database]
insert into [boards]([boardname],[boardcategory]) values (@p0, @p1)
select [t0].[boardid]
from [boards] as [t0]
where [t0].[boardid] = (scope_identity())
-- @p0: input ansistring (size = 6; prec =0; scale = 0) [oracle]
-- @p1: input int32 (size = 0; prec = 0;scale = 0) [23]
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