sql - 如何从另一个表 SQL 服务器查询中选择 2 个变量

Question

好的问题在这里

表 1：

Id1, Id2

表 2

Id, Username

现在 thisTable 1 Id1和Id2variables 是唯一的键Table 2

我想选择Table 1所有值

Username1, Username2

那么我该如何编写这个查询呢？

完整示例

表格1

1,3
3,5

表 2

1,Furkan
3,Obama
5,USA

结果

Furkan, Obama
Obama, USA

谢谢

Answer 1

尝试这个

这是http://www.sqlfiddle.com/#!2/e10b7/2/0

CREATE TABLE table1
(
     Id1 int  primary key, 
     Id2 int
);

INSERT INTO table1
VALUES (1, 3),
       (3, 5);

CREATE TABLE table2
(
     Id int  primary key, 
     Username varchar(255)
);

INSERT INTO table2
VALUES (1, 'Furkan'),
       (3, 'Obama'),
       (5, 'USA');

您的 SQL 查询

select 
    (select Username 
     from table2 as t2 
     where t2.Id = t1.Id1) as coloum1 ,
    (select Username 
     from table2 as t2 
     where t2.Id = t1.Id2) as coloum2 
from table1 as t1

Answer 2

SELECT table2_1.Username AS Username1, table2_2.Username AS Username2
FROM table1
JOIN table2 AS table2_1 ON table1.Id1 = table2_1.Id
JOIN table2 AS table2_2 ON table1.Id2 = table2_2.Id

Answer 3

请参阅SQL Fiddle以获取实时示例

SELECT a.Username AS name_1, b.Username AS name_2 FROM
  t1 JOIN t2 AS a ON t1.Id1 = a.Id
     JOIN t2 AS b ON t1.Id2 = b.Id