1.Mybatis动态sql是基于OGNL的表达式，可以使我们方便的在sql语句中实现某些逻辑。

2.使用if+where实现多条件查询

1〉dao层方法

//if动态sql查询    public List
     
       findByIf(User user);
     

2〉xml配置文件的sql语句

                 SELECT  * FROM  user                                     and userName like concat('%',#{userName},'%')                                                    and userPassword=#{userPassword}                        

3〉测试方法

//if动态sql查询    @Test    public  void  findByIf(){        SqlSession sqlSession = null;        User user = new User();        user.setUserName("测");        //]user.setUserPassword("");        try {            sqlSession = MyBatisUtil.createSqlSession();            List
     
       list = sqlSession.getMapper(IUserDao.class).findByIf(user);            sqlSession.commit();            for (User user1 : list) {                System.out.println("user-------->"+user1.getUserCode()+"\t" +user1.getUserName());            }        } catch (Exception e) {            e.printStackTrace();        }finally {            MyBatisUtil.closeSqlSession(sqlSession);        }    }
     

 3.choose，相当于java中的switch，通常与otherwise搭配

1〉dao层方法

//智能标签choose查询    public List
     
       findByChoose(User user);
     

2〉xml配置文件中的sql语句

                 SELECT  * FROM  user                                                        and userName like concat('%',#{userName},'%')                                                    and userPassword=#{userPassword}                                                        

3〉测试方法

//choose动态sql查询    @Test    public  void  findByChoose(){        SqlSession sqlSession = null;        User user = new User();        user.setUserName("测");        //]user.setUserPassword("");        try {            sqlSession = MyBatisUtil.createSqlSession();            List
     
       list = sqlSession.getMapper(IUserDao.class).findByChoose(user);            sqlSession.commit();            for (User user1 : list) {                System.out.println("user-------->"+user1.getUserCode()+"\t" +user1.getUserName());            }        } catch (Exception e) {            e.printStackTrace();        }finally {            MyBatisUtil.closeSqlSession(sqlSession);        }    }
     

4. （1）foreach：迭代一个集合，通常用于in条件------------->传入数组  array

1〉dao层方法

//智能标签foreach查询 String [] array    public List
     
       findByForeach(String [] depIds);
     

2〉xml配置文件的sql语句

                 SELECT  * FROM  user WHERE  depId in                    #{depIds}            

3〉测试方法

//foreach动态sql查询   array    @Test    public  void  findByForeach(){        SqlSession sqlSession = null;        String [] depIds = {"1","2"};        try {            sqlSession = MyBatisUtil.createSqlSession();            List
     
       list = sqlSession.getMapper(IUserDao.class).findByForeach(depIds);            sqlSession.commit();            for (User user1 : list) {                System.out.println("user-------->"+user1.getUserCode()+"\t" +user1.getUserName());            }        } catch (Exception e) {            e.printStackTrace();        }finally {            MyBatisUtil.closeSqlSession(sqlSession);        }    }
     

（2）foreach传入集合----------->list

1〉dao方法

//智能标签foreach查询 List
     
       list    public  List
      
        findByForeachList(List
       
         list);
       
      
     

2〉xml文件的配置

                 SELECT  * FROM  user WHERE  depId in                    #{depIds}            

3〉测试方法

//foreach动态sql查询   list    @Test    public  void  findByForeachList(){        SqlSession sqlSession = null;       List
     
       list = new ArrayList
      
       ();       list.add(1);        try {            sqlSession = MyBatisUtil.createSqlSession();            List
       
         list1 = sqlSession.getMapper(IUserDao.class).findByForeachList(list);            sqlSession.commit();            for (User user3 : list1) {                System.out.println("user-------->"+user3.getUserCode()+"\t" +user3.getUserName());            }        } catch (Exception e) {            e.printStackTrace();        }finally {            MyBatisUtil.closeSqlSession(sqlSession);        }    }