如果存在多个默认值，请避免使用默认值，或者选择Mysql中的现有单个值

问题描述：

In my website, I have a product image display region. When a user click on a product, it will redirect to the image display page. I had set a default image. Which will display when user see the product. But when the user go to the product image page, I don't want to show the default image, if there exist more than one image. But I need to show the default image if there exist only one image in the database. Currently I am doing this with two queries. Is there any way to do this with a single query?

I need something like

select image from table where if exists more than 1 then select 'non-featured' else select 'featured'

Please help

在我的网站上，我有一个产品图片显示区域。当用户点击产品时，它将重定向到图像显示页面。我设置了默认图像。当用户看到产品时会显示哪个。但是当用户转到产品图像页面时，如果存在多个图像，我不想显示默认图像。但是如果数据库中只有一个图像，我需要显示默认图像。目前我正在做两个查询。有没有办法用一个查询来做到这一点？ p>

我需要类似 p>

 从表中选择图像，如果存在多于 1然后选择'非特色'，否则选择'精选'
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 请帮助 p> 
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答

You can work yourself around by using the group function max(). This function should always return you just 1 image, if it can find it. Otherwise it will return null. Then use the function ifnull() to get your default image.

select ifnull(max(image),'default_image.jpg') from table

如果存在多个默认值，请避免使用默认值，或者选择Mysql中的现有单个值

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