MySql 基于条件的连接查询

Question

I have two tables. These tables have a few matching fields. I would like to fetch them with two conditions.

First one is if a.site_id = b.site_id , as this is our foreign key.

Second is a.Show_Link_back=b.Show_Link_back=1 .

Below is my current query, but with this query I am not getting the right data like first table (a) doesn't responding with data .

Here is the structure of tables

First table fields:

• site_id
• Link_back_Image_URL
• Link_back_Title
• Show_Link_back

Second table fields

• site_id
• Link_back_Image_URL
• Link_back_Title
• Show_Link_back

I would like to make a relation whether site_id is a foreign key and Show_Link_back value is 1 for both table ?

Current query

SELECT a.site_id, a.Link_back_Image_URL, a.Link_back_Title, 
       a.Link_back_Description, a.Link_back_URL, a.Show_Link_back,
       b.Link_back_Image_URL, b.Link_back_Title,
       b.Link_back_Description, b.Link_back_URL
    FROM download_site a, product_listing b
    WHERE a.site_id = b.site_id 
      AND (a.Show_Link_back=1 or b.Show_Link_back=1)

Here is a small query for both table

CREATE TABLE table1
    (`site_id` int(10), `Link_back_Image_URL` varchar(55), 
     `Link_back_Title` varchar(55),`Link_back_Description` varchar(55),
     `Link_back_URL` varchar(55),`Show_Link_back` int(2));

INSERT INTO table1
    (`site_id`, `Link_back_Image_URL`, `Link_back_Title`,
     `Link_back_Description`,`Link_back_URL`,`Show_Link_back`)
VALUES
    (1, 'test', 'test_title','test_desc','test_url','1'),
    (2, 'test', 'test_title','test_desc','test_url','0'),
    (3, 'test', 'test_title','test_desc','test_url','1');

CREATE TABLE table2
    (`site_id` int(10), `Link_back_Image_URL` varchar(55),
     `Link_back_Title` varchar(55),`Link_back_Description` varchar(55),
     `Link_back_URL` varchar(55),`Show_Link_back` int(2));

INSERT INTO table2
    (`site_id`, `Link_back_Image_URL`, `Link_back_Title`,
     `Link_back_Description`,`Link_back_URL`,`Show_Link_back`)
VALUES
    (1, 'test', 'test_title','test_desc','test_url','1'),
    (2, 'test', 'test_title','test_desc','test_url','0'),
    (3, 'test', 'test_title','test_desc','test_url','1');

Answer 1

Looks good to me. 2 out of 3 rows come back

SELECT a.site_id,a.Show_Link_back as ASLB,b.Show_Link_back as BSLB,
a.Link_back_Image_URL, a.Link_back_Title,a.Link_back_Description,a.Link_back_URL, b.Link_back_Image_URL,b.Link_back_Title,b.Link_back_Description,b.Link_back_URL
FROM table1 a
join table2 b
on a.site_id=b.site_id
where a.Show_Link_back=1 and b.Show_Link_back=1

+---------+------+------+---------------------+-----------------+-----------------------+---------------+---------------------+-----------------+-----------------------+---------------+
| site_id | ASLB | BSLB | Link_back_Image_URL | Link_back_Title | Link_back_Description | Link_back_URL | Link_back_Image_URL | Link_back_Title | Link_back_Description | Link_back_URL |
+---------+------+------+---------------------+-----------------+-----------------------+---------------+---------------------+-----------------+-----------------------+---------------+
|       1 |    1 |    1 | test                | test_title      | test_desc             | test_url      | test                | test_title      | test_desc             | test_url      |
|       3 |    1 |    1 | test                | test_title      | test_desc             | test_url      | test                | test_title      | test_desc             | test_url      |
+---------+------+------+---------------------+-----------------+-----------------------+---------------+---------------------+-----------------+-----------------------+---------------+

Note the aliases used in columns 2 and 3 to make some sense of it all.