Question

我有3个表：用户，项目和锁定项目

我想显示项中的所有内容，但如果用户想要隐藏项目，那么我将其userid和itemid添加到锁定列表

[users]
userid
username

[items]
itemid
itemname

[lockeditems]
itemid
userid

SQLSERVER，如何选择所有[项目]，但不要通过[itemid]和[userid]显示项目锁定列表中的项目？

谢谢，抱歉没有格式化

Answer 1

SQL Fiddle

MS SQL Server 2008架构设置：

CREATE TABLE users
    ([userid] int, [username] varchar(4))
;

INSERT INTO users
    ([userid], [username])
VALUES
    (1, 'John'),
    (2, 'Mary')
;

CREATE TABLE items
    ([itemid] int, [itemname] varchar(6))
;

INSERT INTO items
    ([itemid], [itemname])
VALUES
    (1, 'saw'),
    (2, 'hammer')
;

CREATE TABLE lockeditems
    ([itemid] int, [userid] int)
;

INSERT INTO lockeditems
    ([itemid], [userid])
VALUES
    (1, 1)
;

查询1 ：

select u.userid, i.*
from users u
cross join items i 
left outer join lockeditems l on u.userid = l.userid and i.itemid = l.itemid
where l.userid is null

<强> Results ：

| USERID | ITEMID | ITEMNAME |
|--------|--------|----------|
|      1 |      2 |   hammer |
|      2 |      1 |      saw |
|      2 |      2 |   hammer |

Answer 2

假设你有一个变量中的用户，比如说@TheUserId，那么这是对not exists子句的一个很好的用法：

select i.*
from items i
where not exists (select 1
                  from lockeditems li
                  where li.userid = @TheUserId and
                        li.itemid = i.itemid
                 );

Answer 3

这应该这样做：

SELECT * 
    FROM Users u 
    CROSS JOIN Items i
WHERE NOT EXISTS
    (SELECT * 
     FROM lockeditems li
     WHERE li.userID = u.userid AND i.itemid = li.itemid);

Except也可以使用

SELECT  u.UserId, i.ItemId 
    FROM Users u 
    CROSS JOIN Items i
EXCEPT
    SELECT li.UserId, li.ItemID
     FROM lockeditems li;

SqlFiddle here

Answer 4

CREATE TABLE users (  
userid int,
username varchar(20))

CREATE TABLE  items (
itemid int,
itemname varchar(20))

CREATE TABLE lockeditems (
itemid int,
userid int)

INSERT INTO users VALUES  (1,'Adam'),(2,'Johan'),(3,'Jennifer'),(4,'Rajanand'),(5,'Jason')
INSERT INTO items VALUES  (10,'Keyboard'),(20,'Mouse'),(30,'CPU'),(40,'Hard drive'),(50,'RAM')
INSERT INTO lockeditems VALUES (30,3),(50,5)

SELECT * FROM users WHERE userid NOT IN (SELECT userid FROM lockeditems)
SELECT * FROM items WHERE itemid NOT IN (SELECT itemid FROM lockeditems)

Sqlserver - 三个表和禁止列表

4 个答案: