从存储过程中的表中返回所有 id答案

【问题标题】：Return all id's from table in store procedure从存储过程中的表中返回所有 id
【发布时间】：2016-03-22 14:52:05
【问题描述】：

我继续发现SQL 和存储过程，遇到@feedid 仅返回1 个id 的麻烦，但它有前任。 20.如何返回id数组？

CREATE PROC spGetItemsByUser
    @userName NVARCHAR(50)
AS BEGIN

    DECLARE @userId INT,
            @feedId INT;

    SELECT @userId = ID
    FROM users
    WHERE name = @userName

    SELECT @feedId = feedid
    FROM userstofeed
    WHERE userid = @userId

    SELECT *
    FROM feed
    WHERE ID = @feedId

END

【问题讨论】：

标签： sql sql-server tsql stored-procedures

【解决方案1】：

你必须使用 table 变量：

declare @userId table (uid int)
declare @feedId table (id int)

insert into @userid(uid)
select id 
from Users 
where name = @userName

insert into @feedid(id)
select feedid 
from userstofeed 
where userid in (select uid from @userId)

select * from feed where id in (select id from @feedId)

【讨论】：

【解决方案2】：

或者只是简单的加入

create proc spGetItemsByUser
    @userName nvarchar(50)
as
begin

    select * from Users usr
    join UsersToFeed utf on usr.id = utf.userID
    join feed fee on utf.feedid = fee.id
    where usr.name = @userName
end

【讨论】：

【解决方案3】：

CREATE PROC spGetItemsByUser
(
    @userName NVARCHAR(50)
)
AS BEGIN

    SET NOCOUNT ON;

    DECLARE @userId INT

    SELECT @userId = ID
    FROM users
    WHERE name = @userName

    SELECT *
    FROM feed f
    WHERE EXISTS(
        SELECT *
        FROM userstofeed uf
        WHERE f.ID = uf.feedid
            AND uf.userid = @userId
    ) 

END

【讨论】：

【解决方案4】：

问题是您尝试分步执行此操作。您的变量在任何给定时间都只会保存一个变量，即使您在具有多个结果的SELECT 查询中设置它也是如此。只需将这些全部放入一个查询中，您就可以了：

SELECT
    F.feed_id,
    F.other_columns    -- NEVER use SELECT *
FROM
    Users U
INNER JOIN UsersToFeed UTF ON UTF.userid = U.userid
INNER JOIN Feed F ON F.feedid = UTF.feedid
WHERE
    U.UserName = @UserName

【讨论】：

【解决方案5】：

CREATE PROC spGetItemsByUser
    @userName NVARCHAR(50)
AS BEGIN

    DECLARE @userId INT,
            @feedId INT;

    SELECT @userId = ID
    FROM users
    WHERE name = @userName

    SELECT *
    FROM feed
    WHERE ID IN (
        SELECT feedid
        FROM userstofeed
        WHERE userid = @userId
    )

END

【讨论】：