动态SQL语句是核心之一,这里我们通过几个示例来演示

一 多条件查询专题

1.通过恒等式完成动态SQL语句

涉及到if标签

<mapper namespace="com.shxt.model.User"><resultMap type="com.shxt.model.User" id="BaseResultMapper"><id column="user_id" property="user_id" /><result column="user_name" property="user_name" /><result column="sex" property="sex" /><result column="money" property="money" /><result column="birthday" property="birthday" /></resultMap><sql id="oa_user_columns">user_id,user_name,sex,money,birthday</sql><sql id="oa_user_columns_alias">${alias}.user_id,${alias}.user_name,${alias}.sex,${alias}.money,${alias}.birthday</sql>
</mapper>

• 映射文件

    <!-- 1.姓名和性别的条件查询 --><!-- A.通过恒等式完成动态SQL语句 --><select id="if01" parameterType="map" resultMap="BaseResultMapper">SELECT<include refid="oa_user_columns" />FROMoa_userWHERE 1=1<if test="name != null && name != ''">AND user_name LIKE CONCAT('%',#{name},'%')</if><if test="sex != null and sex != ''">AND sex=#{sex}</if></select>

• Java测试代码

    @Testpublic void IF标签01(){SqlSession sqlSession = null;try {sqlSession = MyBatisUtils.getSqlSession();Map<String,Object> query = new HashMap<>();query.put("name", "悟");query.put("sex", "男");List<User> userList =sqlSession.selectList(User.class.getName()+".if01", query);System.out.println(userList);} finally {MyBatisUtils.closeSqlSession(sqlSession);}}

• 图解说明
  

2.where标签和if标签组合

• 如果发现标签內有内容,那么会在内容的最前面加入关键字 where
• 如果有内容,会检查内容的最前面是否含有 AND空格 或者 OR空格 ,自动将其抹掉
• 映射文件

    <!-- B.推荐方式 WHERE标签 --><select id="if02" parameterType="map" resultMap="BaseResultMapper">SELECT<include refid="oa_user_columns" />FROMoa_user<where><if test="name != null && name != ''">AND      user_name LIKE CONCAT('%',#{name},'%')</if><if test="sex != null and sex != ''">AND sex=#{sex}</if></where></select>

• Java测试代码

    @Testpublic void IF标签02(){SqlSession sqlSession = null;try {sqlSession = MyBatisUtils.getSqlSession();Map<String,Object> query = new HashMap<>();query.put("name", "悟");query.put("sex", "男");List<User> userList =sqlSession.selectList(User.class.getName()+".if02", query);System.out.println(userList);} finally {MyBatisUtils.closeSqlSession(sqlSession);}}

• 图解说明

3.trim标签和if标签

<trimprefix="当发现有内容的时候,你在内容的最前面想加入什么内容"prefixOverrides="当发现有内容的时候,你在内容的最前面想抹掉什么内容"suffix="当发现有内容的时候,你在内容的最后面面想加入什么内容"suffixOverrides="当发现有内容的时候,你在内容的最后面想抹掉什么内容">
</trim>

• 映射文件

     <!-- C.trim标签 --><select id="if03" parameterType="map" resultMap="BaseResultMapper">SELECT<include refid="oa_user_columns" />FROMoa_user<trim prefix="WHERE " prefixOverrides="AND |OR "><if test="name != null && name != ''">AND user_name LIKE CONCAT('%',#{name},'%')</if><if test="sex != null and sex != ''">AND sex=#{sex}</if></trim></select>

• Java测试代码

    @Testpublic void trim标签(){SqlSession sqlSession = null;try {sqlSession = MyBatisUtils.getSqlSession();Map<String,Object> query = new HashMap<>();query.put("name", "悟");query.put("sex", "男");List<User> userList =sqlSession.selectList(User.class.getName()+".if03", query);System.out.println(userList);} finally {MyBatisUtils.closeSqlSession(sqlSession);}}

• 图解说明
  

二 更新操作

1.set标签

• 当你发现有内容的时候,在内容的最前面加入 set
• 当你发现有内容的时候,检查内容的最后面是否有逗号"," 如果将其抹掉
• 映射文件

    <update id="update01" parameterType="com.shxt.model.User">UPDATEoa_user<set><if test="user_name != null and user_name != ''">user_name=#{user_name},</if><if test="sex != null and sex != ''">sex=#{sex},</if><if test="money != null">money=#{money},</if><if test="birthday != null">birthday=#{birthday},</if></set>WHEREuser_id=#{user_id}</update>

• Java测试代码

    @Testpublic void 更新操作_变更数据库(){SqlSession sqlSession = null;try {sqlSession = MyBatisUtils.getSqlSession();//数据User user = new User();user.setUser_id(3);user.setUser_name("天蓬元帅");//日期的转换String date = "1998-09-09";DateFormat df = new SimpleDateFormat("yyyy-MM-dd");user.setBirthday(df.parse(date));int row =sqlSession.update(User.class.getName()+".update01", user);System.out.println(row);//事务的提交sqlSession.commit();}catch (Exception ex) {ex.printStackTrace();}finally {MyBatisUtils.closeSqlSession(sqlSession);}}

• 图解说明
  

2.trim标签完成更新

• 映射文件

    <update id="update02" parameterType="com.shxt.model.User">UPDATEoa_user<trim prefix="SET " suffixOverrides=","><if test="user_name != null and user_name != ''">user_name=#{user_name},</if><if test="sex != null and sex != ''">sex=#{sex},</if><if test="money != null">money=#{money},</if><if test="birthday != null">birthday=#{birthday},</if></trim>WHEREuser_id=#{user_id}</update>

• Java测试代码

    @Testpublic void 更新操作_TRIM标签_变更数据库(){SqlSession sqlSession = null;try {sqlSession = MyBatisUtils.getSqlSession();//数据User user = new User();user.setUser_id(3);user.setUser_name("天蓬元帅123");//日期的转换String date = "1998-10-09";DateFormat df = new SimpleDateFormat("yyyy-MM-dd");user.setBirthday(df.parse(date));int row =sqlSession.update(User.class.getName()+".update02", user);System.out.println(row);//事务的提交sqlSession.commit();}catch (Exception ex) {ex.printStackTrace();}finally {MyBatisUtils.closeSqlSession(sqlSession);}}

三 choose 标签简单使用

• 映射文件

    <select id="choose01" parameterType="map" resultMap="BaseResultMapper">SELECT<include refid="oa_user_columns"/>FROMoa_userWHERE<choose><when test='sex != null and sex=="男"'>money>777</when><when test='sex != null and sex=="女"'>money>666</when><otherwise>1=1</otherwise></choose></select>

• Java测试代码

    @Testpublic void choose标签(){SqlSession sqlSession = null;try {sqlSession = MyBatisUtils.getSqlSession();Map<String,Object> query = new HashMap<>();query.put("sex", "女123213");List<User> userList =sqlSession.selectList(User.class.getName()+".choose01", query);System.out.println(userList);} finally {MyBatisUtils.closeSqlSession(sqlSession);}}

四 小于号问题

• 映射文件

    <select id="less01" parameterType="double" resultMap="BaseResultMapper">SELECT<include refid="oa_user_columns"/>FROM oa_userWHEREmoney <= #{money}</select><select id="less02" parameterType="double" resultMap="BaseResultMapper">SELECT<include refid="oa_user_columns"/>FROM oa_userWHERE<!-- 里面不能包含标签 --><![CDATA[money <= #{money}]]></select>

• Java测试代码

    @Testpublic void 小于号的解决问题(){SqlSession sqlSession = null;try {sqlSession = MyBatisUtils.getSqlSession();List<User> userList =sqlSession.selectList(User.class.getName()+".less01", 1.0*800);System.out.println(userList);userList =sqlSession.selectList(User.class.getName()+".less02",  1.0*600);System.out.println(userList);} finally {MyBatisUtils.closeSqlSession(sqlSession);}}

• 图解说明
  

请参考附录1说明

五 动态添加语句

• 映射文件

    <insert id="add01" parameterType="com.shxt.model.User"useGeneratedKeys="true" keyProperty="user_id">INSERT INTO oa_user<trim prefix="(" suffix=")" suffixOverrides=","><if test="user_name != null and user_name!=''">user_name,</if><if test="sex != null and sex!=''">sex,</if><if test="money != null">money,</if><if test="birthday != null">birthday,</if></trim><trim prefix="VALUES (" suffix=")" suffixOverrides=","><if test="user_name != null and user_name!=''">#{user_name},</if><if test="sex != null and sex!=''">#{sex},</if><if test="money != null">#{money},</if><if test="birthday != null">#{birthday},</if></trim></insert>

• Java测试代码

    @Testpublic void 动态的添加语句(){SqlSession sqlSession = null;try {sqlSession = MyBatisUtils.getSqlSession();//数据User user = new User();user.setUser_name("刘备12333333");//日期的转换String date = "1998-10-09";DateFormat df = new SimpleDateFormat("yyyy-MM-dd");user.setBirthday(df.parse(date));user.setMoney(1111.11);int row =sqlSession.insert(User.class.getName()+".add01", user);System.out.println(row);//事务的提交sqlSession.commit();System.out.println(user);}catch (Exception ex) {ex.printStackTrace();}finally {MyBatisUtils.closeSqlSession(sqlSession);}}

六 foreach标签

1.数组方式

• 映射方式

    <!-- 数组删除,如果数组的话,请不要去设置paramterType,让其自动识别 --><delete id="delete01" >DELETE FROMoa_userWHERE user_id in <!-- 对数组进行遍历 如果你只是传了一个数组或者一个集合collection="array|list"--><foreach collection="array" item="shxt"open="(" close=")" separator=",">#{shxt}</foreach></delete>

• Java测试代码

    @Testpublic void 传递数组删除规则(){SqlSession sqlSession = null;try {sqlSession = MyBatisUtils.getSqlSession();int row = sqlSession.delete(User.class.getName()+".delete01", new int[]{5,6});//事务的提交sqlSession.commit();System.out.println(row);}catch (Exception ex) {ex.printStackTrace();}finally {MyBatisUtils.closeSqlSession(sqlSession);}}

2.List方式

• 映射文件

     <!-- List集合 --><delete id="delete02" parameterType="list">DELETE FROMoa_userWHERE user_id in <foreach collection="list" item="shxt"open="(" close=")" separator=",">#{shxt}</foreach></delete>

• Java测试代码

    @Testpublic void 传递集合删除规则(){SqlSession sqlSession = null;try {sqlSession = MyBatisUtils.getSqlSession();List<Integer> tempList = new ArrayList<>();tempList.add(8);tempList.add(9);int row = sqlSession.delete(User.class.getName()+".delete02", tempList);//事务的提交sqlSession.commit();System.out.println(row);}catch (Exception ex) {ex.printStackTrace();}finally {MyBatisUtils.closeSqlSession(sqlSession);}}

3.Map方式

• 映射方式

    <delete id="delete03" parameterType="map">DELETE FROMoa_userWHERE user_id in <foreach collection="id_array" item="shxt"open="(" close=")" separator=",">#{shxt}</foreach></delete>

• Java测试代码

    @Testpublic void 传递Map删除规则(){SqlSession sqlSession = null;try {sqlSession = MyBatisUtils.getSqlSession();List<Integer> tempList = new ArrayList<>();tempList.add(7);tempList.add(10);Map<String, Object> map = new HashMap<String, Object>();map.put("id_array", tempList);int row = sqlSession.delete(User.class.getName()+".delete03", map);//事务的提交sqlSession.commit();System.out.println(row);}catch (Exception ex) {ex.printStackTrace();}finally {MyBatisUtils.closeSqlSession(sqlSession);}}

• 图解方式
  

4.批量添加

• 映射文件

    <insert id="add02" parameterType="list">INSERT INTOoa_userVALUES<foreach collection="list" item="user" separator=",">(#{user.user_name},#{user.sex},#{user.money})</foreach></insert>

附录1 : MyBatis在xml文件中处理大于号小于号的方法

第一种方法：

用了转义字符把>和<替换掉，然后就没有问题了。

SELECT * FROM test WHERE 1 = 1 AND start_date  <= CURRENT_DATE AND end_date >= CURRENT_DATE

附：XML转义字符

第二种方法

因为这个是xml格式的，所以不允许出现类似“>”这样的字符，但是都可以使用<![CDATA[ ]]>符号进行说明，将此类符号不进行解析
你的可以写成这个：
mapper文件示例代码

<![CDATA[ when min(starttime)<='12:00' and max(endtime)<='12:00' ]]>