mybatis 三：动态SQL

重点标签有：
            

 

if标签：

     resultType="Blog">
  SELECT * FROM BLOG 
  WHERE state = ‘ACTIVE’ 
      
    AND title like #{title}
  

choos标签：

  SELECT * FROM BLOG WHERE state = ‘ACTIVE’
  
    
      AND title like #{title}
    
    
      AND author_name like #{author.name}
    
    
      AND featured = 1
    
  

when标签：（常用） 

会当if不成立的时候忽略and/or

  SELECT * FROM BLOG 
  WHERE                 
  
    state = #{state}
   
  
    AND title like #{title}
  
  
    AND author_name like #{author.name}
  

  SELECT * FROM BLOG 
   
    
         state = #{state}
     
    
        AND title like #{title}
    
    
        AND author_name like #{author.name}
    
  

set标签：

set 元素可以用于动态包含需要更新的列，set会忽略最后一个逗号

  update Author
                    
      username=#{username},
      password=#{password},
      email=#{email},
      bio=#{bio}
    
  where id=#{id}

trim ：可以代替where和set

foreach：循环迭代

        #{item}
  

例子：

select * from UserInfo
		
		
			and userName=#{userName}
		
		
			and userSex=#{userSex}
		
		
			and userAge=#{userAge}
		
		

 

在给方法起名时的规范：

添加：addXxx   saveXxx

更新：updateXxx

删除：deleteXxx

查找：findXxx    searchXxx