Question

我正在为网站创建简单的横幅跟踪代码。这可以正常工作，但是两个客户端在随机查询中占主导地位，因为它们在此位置具有多个横幅。有时，他们会显示出三分之二或三分之三的信息，这并不是客户想要的。这是我当前对该视图的查询。

SELECT * FROM banners 
WHERE location like '["2"]'
AND published = '1'
ORDER BY rand() 
LIMIT 3;

我还有一个名为client的字段。我只想在其位置与“ [“ 2”]'相匹配的时间内选择其中一个横幅。预先感谢。

| published | location | client  | img                 |
|-----------|----------|---------|---------------------|
| 1         | ["2"]    | ClientA | /banners/image1.jpg |
| 1         | ["2"]    | ClientA | /banners/image2.jpg |
| 1         | ["2"]    | ClientA | /banners/image3.jpg |
| 1         | ["2"]    | ClientB | /banners/image4.jpg |
| 1         | ["2"]    | ClientC | /banners/image5.jpg |
| 1         | ["2"]    | ClientD | /banners/image6.jpg |

Answer 1

使用您的示例：

create table banners (
    published int,
    location varchar(10),
    client varchar(10), 
    img varchar(100)
);

insert into banners values
(1, '["2"]', 'ClientA', '/banners/image1.jpg'),
(1, '["2"]', 'ClientA', '/banners/image2.jpg'),
(1, '["2"]', 'ClientA', '/banners/image3.jpg'),
(1, '["2"]', 'ClientB', '/banners/image4.jpg'),
(1, '["2"]', 'ClientC', '/banners/image5.jpg'),
(1, '["2"]', 'ClientD', '/banners/image6.jpg');

您可以使用的一种方法是使用这种方法：

-- we'll use a temporary table to store some data
-- if that table exists, let's drop it first.
-- you can change the name from banners_007 to something else

drop table if exists banners_007;

-- create that table to store data temporarily
-- store all data from banners and add a random number to each row

create table if not exists banners_007 as 
select *, rand() as randomnumber from banners;

-- get client and the lowest random number
-- and get all records for that client (you'll get 1 record per client)
-- order those clients randomly
-- get the top 3 records

select a.* from banners_007 a
inner join (

  select client, min(randomnumber) as min_rn
  from banners_007
  group by client

) b on a.client = b.client and a.randomnumber = b.min_rn
order by rand()
limit 3;

示例在这里：https://rextester.com/ZTGED79700

MySQL视图不超过一种类型

1 个答案: