1、動態sql

1.1、if

需求：查詢全部用戶，如果用戶填寫了姓名，按照姓名的模糊查詢，如果用戶填寫了姓名和年齡，則按姓名和年齡一起查找

1、接口定義

public List<User> querybyUser(User vo) throws Exception;

2、mapper.xml配置

<select id = "querybyUser" resultMap="UserMap">
    select * from tb_user where 1=1
    <if test="userName!=null and userName!=‘‘">
       and user_Name like #{userName}
    </if>
    <if test = "age!=null">
        and age =#{age}
    </if>
  </select>
 

3、測試方法

@Test
    public void testIf()throws Exception{
        User user = new User();
        user.setUserName(null);
        user.setAge(17);
        List<User> list = userMapper.querybyUser(user);
        for (User u : list) {
            System.out.println(u);
        }
    }

4、日誌

DEBUG - Opening JDBC Connection
DEBUG - Created connection 276327391.
DEBUG - Setting autocommit to false on JDBC Connection [oracle.jdbc.driver.T4CConnection@10786bdf]
DEBUG - ==>  Preparing: select * from tb_user where 1=1 and age =? 
DEBUG - ==> Parameters: 17(Integer)
DEBUG - <==      Total: 1
User [userid=10, userName=阿珂3, pwd=123456, age=17, sex=女, birthday=Mon Aug 13 14:57:50 CST 2018]
DEBUG - Resetting autocommit to true on JDBC Connection [oracle.jdbc.driver.T4CConnection@10786bdf]
DEBUG - Closing JDBC Connection [oracle.jdbc.driver.T4CConnection@10786bdf]
DEBUG - Returned connection 276327391 to pool.
 

1.2、where

在前面的sql中的我們認為的定義了一個where 1=1這樣的東西，此時我們可以通過mybatis的where標簽來搞定

<select id = "querybyUser" resultMap="UserMap">
    select * from tb_user 
    <where>
        <if test="userName!=null and userName!=‘‘">
            and user_Name like #{userName}
        </if>
        <if test = "age!=null">
            and age =#{age}
        </if>
    </where>

  </select>
 

where :自動根據需求生成，並且可以剔除不需要and

直接測試即可

1.3、foreach

另外一個動態 SQL 通用的必要操作是叠代一個集合, 通常是構建在 IN 條件中的。

接口方法定義

public List<User> querybyIn(QueryUser vo) throws Exception;

mapper.xml

<select id = "querybyIn" resultMap="UserMap">
        select * from tb_user
        <where>
            <if test="userids!=null">
                <!-- 
                    collection:要叠代集合或者數組
                -->
                <foreach collection="userids" open="userid in (" close=")" separator="," item="userid">
                    #{userid}
                </foreach>
            </if>
        </where>
  </select>

測試方法

@Test
    public void testforeach()throws Exception{
        QueryUser queryUser= new QueryUser();
        queryUser.setUserids(new int[]{8,9,2,3});
        List<User> list = userMapper.querybyIn(queryUser);
        for (User u : list) {
            System.out.println(u);
        }
    }

日誌

DEBUG - Opening JDBC Connection
DEBUG - Created connection 1060925979.
DEBUG - Setting autocommit to false on JDBC Connection [oracle.jdbc.driver.T4CConnection@3f3c721b]
DEBUG - ==>  Preparing: select * from tb_user WHERE userid in ( ? , ? , ? , ? ) 
DEBUG - ==> Parameters: 8(Integer), 9(Integer), 2(Integer), 3(Integer)
DEBUG - <==      Total: 4
User [userid=8, userName=阿珂, pwd=123456, age=18, sex=女, birthday=Mon Aug 13 14:06:14 CST 2018]
User [userid=9, userName=阿珂2, pwd=123456, age=18, sex=女, birthday=Mon Aug 13 14:56:45 CST 2018]
User [userid=2, userName=張三, pwd=123456, age=10, sex=男, birthday=Mon Aug 13 10:07:55 CST 2018]
User [userid=3, userName=李四, pwd=123456, age=10, sex=男, birthday=Mon Aug 13 10:07:55 CST 2018]
DEBUG - Resetting autocommit to true on JDBC Connection [oracle.jdbc.driver.T4CConnection@3f3c721b]
DEBUG - Closing JDBC Connection [oracle.jdbc.driver.T4CConnection@3f3c721b]
DEBUG - Returned connection 1060925979 to pool.

1.4、Set

set 元素可以被用於動態包含更新的列,而不包含不需更新的(動態更新)

接口定義

public int dycUpdate(User vo) throws Exception;

mapper.xml定義

<update id="dycUpdate">
    update tb_user
    <set>
        <if test="userName!=null and userName!=‘‘">
            user_name=#{userName},
        </if>
        <if test="pwd!=null and pwd!=‘‘">
            pwd=#{pwd},
        </if>
        <if test="age!=null">
            age=#{age},
        </if>
        <if test="sex!=null">
            sex=#{sex},
        </if>
        <if test="birthday!=null">
            birthday=#{birthday},
        </if>
    </set>
    where userid=#{userid}
  </update>

測試方法

@Test
    public void testdycUpdate()throws Exception{
        User user = new User();
        user.setUserName("hello");
        user.setSex("男");
        user.setBirthday(new Date());
        user.setUserid(8);
        userMapper.dycUpdate(user);
        sqlSession.commit();
    }

日誌

DEBUG - Opening JDBC Connection
DEBUG - Created connection 340839523.
DEBUG - Setting autocommit to false on JDBC Connection [oracle.jdbc.driver.T4CConnection@1450cc63]
DEBUG - ==>  Preparing: update tb_user SET user_name=?, sex=?, birthday=? where userid=? 
DEBUG - ==> Parameters: hello(String), 男(String), 2018-08-14 10:19:19.311(Timestamp), 8(Integer)
DEBUG - <==    Updates: 1
DEBUG - Committing JDBC Connection [oracle.jdbc.driver.T4CConnection@1450cc63]
DEBUG - Resetting autocommit to true on JDBC Connection [oracle.jdbc.driver.T4CConnection@1450cc63]
DEBUG - Closing JDBC Connection [oracle.jdbc.driver.T4CConnection@1450cc63]
DEBUG - Returned connection 340839523 to pool.

1.5、動態添加

接口定義

public int dycInsert(User vo) throws Exception;

mapper.xml文件

 <insert id="dycInsert">
        insert into tb_user (
                userid,
                <trim suffixOverrides=",">
                    <if test="userName!=null and userName!=‘‘">
                        user_name,
                    </if>
                    <if test="pwd!=null and pwd!=‘‘">
                        pwd,
                    </if>
                    <if test="age!=null">
                        age,
                    </if>
                    <if test="sex!=null">
                        sex,
                    </if>
                    <if test="birthday!=null">
                        birthday,
                    </if>
                </trim>

        ) values(
            seq_user.nextval,
            <trim suffixOverrides=",">
                <if test="userName!=null and userName!=‘‘">
                #{userName},
                </if>
                <if test="pwd!=null and pwd!=‘‘">
                    #{pwd},
                </if>
                <if test="age!=null">
                    #{age},
                </if>
                <if test="sex!=null">
                    #{sex},
                </if>
                <if test="birthday!=null">
                    #{birthday},
                </if>
            </trim>

        )   
  </insert>

測試方法

@Test
    public void testdycInsert()throws Exception{
        User user = new User();
        user.setUserName("yui");
        user.setSex("男");
        user.setBirthday(new Date());
        user.setUserid(8);
        userMapper.dycInsert(user);
        sqlSession.commit();
    }

日誌

DEBUG - Opening JDBC Connection
DEBUG - Created connection 1341177488.
DEBUG - Setting autocommit to false on JDBC Connection [oracle.jdbc.driver.T4CConnection@4ff0be90]
DEBUG - ==>  Preparing: insert into tb_user ( userid, user_name, sex, birthday ) values( seq_user.nextval, ?, ?, ? ) 
DEBUG - ==> Parameters: yui(String), 男(String), 2018-08-14 10:31:06.973(Timestamp)
DEBUG - <==    Updates: 1
DEBUG - Committing JDBC Connection [oracle.jdbc.driver.T4CConnection@4ff0be90]
DEBUG - Resetting autocommit to true on JDBC Connection [oracle.jdbc.driver.T4CConnection@4ff0be90]
DEBUG - Closing JDBC Connection [oracle.jdbc.driver.T4CConnection@4ff0be90]
DEBUG - Returned connection 1341177488 to pool.

1.6、choose、when、otherwise

有時我們不想應用所有的條件, 相反我們想選擇很多情況下的一種。 Java 中的 switch 和 語句相似,MyBatis 提供 choose 元素。

需求：查詢所有用戶

1.如果用戶填寫了性別和姓名，則按姓名查找

2.如果用戶填寫了姓名，按姓名查找

3.如果用戶未填寫姓名，但是填寫了性別，則按性別查找

接口聲明

public List<User> queryDyc(QueryUser vo) throws Exception;

mapper.xml文件

<select id="queryDyc" resultMap="UserMap">
        select * from tb_user
        <where>
            <choose>
                <when test="name!=null and name!=‘‘">
                    user_name=#{name}
                </when>
                <when test="sex!=null and sex!=‘‘">
                    sex=#{sex}
                </when>
                <otherwise>
                    age>5
                </otherwise>
            </choose>
        </where>
  </select>

測試方法

@Test
    public void testIfelse()throws Exception{

        QueryUser queryUser= new QueryUser();
        queryUser.setName(null);
        queryUser.setSex(null);
        List<User> list = userMapper.queryDyc(queryUser);
        for (User u : list) {
            System.out.println(u);
        }
    }

日誌

DEBUG - Opening JDBC Connection
DEBUG - Created connection 480779844.
DEBUG - Setting autocommit to false on JDBC Connection [oracle.jdbc.driver.T4CConnection@1ca81e44]
DEBUG - ==>  Preparing: select * from tb_user WHERE age>5 
DEBUG - ==> Parameters: 
DEBUG - <==      Total: 7
User [userid=8, userName=hello, pwd=123456, age=18, sex=男, birthday=Tue Aug 14 10:19:19 CST 2018]
User [userid=9, userName=阿珂2, pwd=123456, age=18, sex=女, birthday=Mon Aug 13 14:56:45 CST 2018]
User [userid=10, userName=阿珂3, pwd=123456, age=17, sex=女, birthday=Mon Aug 13 14:57:50 CST 2018]
User [userid=2, userName=張三, pwd=123456, age=10, sex=男, birthday=Mon Aug 13 10:07:55 CST 2018]
User [userid=3, userName=李四, pwd=123456, age=10, sex=男, birthday=Mon Aug 13 10:07:55 CST 2018]
User [userid=4, userName=王五, pwd=123456, age=10, sex=男, birthday=Mon Aug 13 10:07:55 CST 2018]
User [userid=5, userName=趙六, pwd=123456, age=10, sex=男, birthday=Mon Aug 13 10:07:55 CST 2018]
DEBUG - Resetting autocommit to true on JDBC Connection [oracle.jdbc.driver.T4CConnection@1ca81e44]
DEBUG - Closing JDBC Connection [oracle.jdbc.driver.T4CConnection@1ca81e44]
DEBUG - Returned connection 480779844 to pool.

1.7、sql片段

sql片段是為了將一些常用的sql語句保存起來，在需要的時候進行引用即可

如果sql片段和statement在同一個命名空間下，則直接引用

 <sql id="basesql">
        select * from tb_user
  </sql>
  <select id="queryDyc" resultMap="UserMap">
        <include refid="basesql"/>
        <where>
            <choose>
                <when test="name!=null and name!=‘‘">
                    user_name=#{name}
                </when>
                <when test="sex!=null and sex!=‘‘">
                    sex=#{sex}
                </when>
                <otherwise>
                    age>5
                </otherwise>
            </choose>
        </where>
  </select>

如果sql片段和statement不在同一個命名空間下，則直接則使用命名空間.sqlid的形式進行引用

 <select id="queryDyc" resultMap="UserMap">
        <include refid="mycomm.baseselect"/>
        <where>
            <choose>
                <when test="name!=null and name!=‘‘">
                    user_name=#{name}
                </when>
                <when test="sex!=null and sex!=‘‘">
                    sex=#{sex}
                </when>
                <otherwise>
                    age>5
                </otherwise>
            </choose>
        </where>
  </select>

MyBatis學習（五）