sql - 重构循环 SQL 插入

Question

此插入语句有效。但是，我希望有人可以教我一种更有效的方法来执行此查询。这就是我得到的...

我有一个名为 Source 的表，其中 DealerID 是一个非唯一 ID(无论如何在这个表中)。对于每个 DealerID，有多个名称。示例:

15  BillBoard
15  Event
15  Newspaper

16  BillBoard
16  Event
16  Newspaper

我知道，我知道。这是一种非常低效的存储数据的方式。我们正在处理遗留应用程序，我现在无法彻底检查此数据结构。所以，我需要做的是为每个 DealerID 添加两条新记录。一种用于“电话”，一种用于“互联网”。所以在插入之后，它看起来像这样:

15  BillBoard
15  Event
15  Newspaper
15  Phone
15  Internet

16  BillBoard
16  Event
16  Newspaper
16  Phone
16  Internet

下面的sql语句可以，但是我想知道有没有更好的方法...

declare @SourceTemp table (
   [Id] int identity (1, 1) not null,
   [DealerId] int
)

insert into @SourceTemp select distinct DealerId from Source where DealerId is not null

declare @dealerid int
declare @rowcount int = 1
declare @idcount int
select @idcount = max(Id) from  @SourceTemp

while @rowcount < (@idcount + 1)
begin
    select @dealerid = DealerId from @SourceTemp where Id = @rowcount

    ---------------- Insert Phone
    if not exists (select * from Source where DealerId = @dealerid and Name = 'Phone')
    begin
        insert into 
        Source 
            ([DealerID],[Name],[Service],[CampaignCode],[Description],[Created],[UserCreated],[Active])
        values
            (@dealerid, 'Phone', 'Generic', 'CampaignCode', NULL, GETDATE(), 0, 1)
    end

    --------------- Insert Internet
    if not exists (select * from Source where DealerId = @dealerid and Name = 'Internet')
    begin
        insert into 
        Source 
            ([DealerID],[Name],[Service],[CampaignCode],[Description],[Created],[UserCreated],[Active])
        values
            (@dealerid, 'Internet', 'Generic', 'CampaignCode', NULL, GETDATE(), 0, 1)
    end

    set @rowcount = @rowcount + 1
end

编辑之后:

我必须对 Tom 的回答做一个小修改，添加 DISTINCT。这有效...

INSERT INTO Source ([DealerID], [Name], [Service], [CampaignCode], [Description], [Created], [UserCreated], [Active])
SELECT DISTINCT
    S.DealerId, SQ.Name, 'Generic', 'CampaignCode', NULL, GETDATE(), 0, 1
FROM
    Source S
CROSS JOIN (SELECT 'Internet' AS Name UNION ALL SELECT 'Phone' AS Name) SQ
WHERE
    NOT EXISTS (SELECT * FROM Source WHERE DealerID = S.DealerID AND Name = SQ.Name)

Answer 1

INSERT INTO Source (DealerID, Name, Service, CampaignCode, Description, ...)
SELECT DISTINCT
    S.DealerID, SQ.Name, ...
FROM
    Source S
CROSS JOIN (SELECT 'Internet' AS Name UNION ALL SELECT 'Phone' AS Name) SQ
WHERE
    NOT EXISTS (SELECT * FROM Source WHERE DealerID = S.DealerID AND Name = SQ.Name)

已更正它以包含 DISTINCT，因为那里的每个 DealerID 都会有多个其他 Name。如果性能有问题，那么您可以将 DISTINCT 向下移动到 Source 表的子查询，然后从那里移动 CROSS JOIN:

INSERT INTO Source (DealerID, Name, Service, CampaignCode, Description, ...)
SELECT DISTINCT
    S.DealerID, SQ.Name, ...
FROM
    (SELECT DISTINCT DealerID
     FROM Source
    ) S
CROSS JOIN (SELECT 'Internet' AS Name UNION ALL SELECT 'Phone' AS Name) SQ
WHERE
    NOT EXISTS (SELECT * FROM Source WHERE DealerID = S.DealerID AND Name = SQ.Name)