Question

我有一个mySQL SELECT语句，其中包含WHERE条件下的全文搜索和普通搜索，以及另外一个JOIN这样的

SELECT 
 customer.*, 
 countries.name as country
 FROM customer  
 LEFT JOIN countries ON countries.ID = customer.country_id 
 WHERE customer.num   = :keyword 
    OR customer.city  = :keyword  
    OR customer.email = :keyword 
    OR MATCH (customer.company) AGAINST (:keyword)
    OR countries.name = :keyword

只要table.column (customer.company)是no result条件的一部分，对countries.name列进行全文搜索的查询就会返回WHERE。但是对countries.name本身的查询是成功的。

如何使用上面示例中所有WHERE组件的组合正确编码SELECT语句以返回成功的查询？

编辑：

在之前的版本中，我使用了这个声明

 SELECT 
  customer.* ,
  countries.name
  FROM customer, countries 
  WHERE customer.country_id=countries.ID 
  AND MATCH (customer.company) AGAINST (:keyword)

  UNION

  SELECT 
  customer.*, 
  countries.name
  FROM customer, countries 
  WHERE customer.country_id=countries.ID 
  AND countries.name=:keyword

运作良好。我只是不知道这是否是使用不同搜索（全文和普通）查询两个表的有效方法。此外，当我搜索超过2列时，代码很容易被炸毁，我想避免。

欢迎任何更多的想法和帮助

Answer 1

您应该检查NULLs，因为您使用的是LEFT JOIN：

SELECT 
     customer.*, 
     countries.name as country
 FROM customer  
 LEFT JOIN countries ON countries.ID = customer.country_id 
 WHERE customer.num   = :keyword 
    OR customer.city  = :keyword  
    OR customer.email = :keyword 
    OR MATCH (customer.company) AGAINST (:keyword)
    OR (countries.name = :keyword OR countries.name IS NULL)

为了澄清，LEFT JOIN右表上的条件只应放在ON子句内，而不是WHERE子句中。这有点不同，因为您要将其与所有其他条件进行比较，因此 - NULL比较。

Answer 2

我的解决方案只是设置默认值= countries.name到CASE WHEN如果它使用(CASE WHEN countries.name is null then 'default value' else countries.name END)

为空

SELECT 
 customer.*, 
 countries.name as country
 FROM customer  
 LEFT JOIN countries ON countries.ID = customer.country_id 
 WHERE customer.num   = :keyword 
    OR customer.city  = :keyword  
    OR customer.email = :keyword 
    OR MATCH (customer.company) AGAINST (:keyword)
    OR (CASE WHEN countries.name is null then '' else countries.name END) = :keyword

新查询

io.of('/').sockets[rcvrId].emit('message', data)

mySQL - 如何正确编写SELECT语句

2 个答案: