设置在查看的sql联接声明中的限制

Question

我在此获取多个单个属性的行，因为我已经离开了联接property_image表，并且它包含多个具有相同属性的图像。

CREATE OR REPLACE VIEW Basic 
AS 
SELECT 
    crawlproperty_images.image_name as property_image 
FROM crawl_properties 
    LEFT JOIN crawlproperty_images 
    ON (crawl_properties.id=crawlproperty_images.crawl_property_id) 

Answer 1

返回您在SQL-SERVER的第一行：

CREATE OR REPLACE VIEW Basic 
AS 
SELECT TOP 1 
crawlproperty_images.image_name as property_image FROM crawl_properties 
LEFT JOIN crawlproperty_images ON (crawl_properties.id=crawlproperty_images.crawl_property_id) 

返回你在MySQL中的第一行：

CREATE OR REPLACE VIEW Basic 
AS 
SELECT 
crawlproperty_images.image_name as property_image FROM crawl_properties 
LEFT JOIN crawlproperty_images ON (crawl_properties.id=crawlproperty_images.crawl_property_id) 
LIMIT 1 

Answer 2

你可以在MySQL中使用LIMIT如下：

CREATE OR REPLACE VIEW Basic 
AS 
SELECT crawlproperty_images.image_name AS property_image 
FROM crawl_properties 
LEFT JOIN crawlproperty_images ON (crawl_properties.id=crawlproperty_images.crawl_property_id) 
LIMIT 1 

Answer 3

你不能把李在加入。但是你可以在查询结尾处使用限制。

例如， select * from table t1 left join table t2 on t1.id = t2.id limit 10