Mybatis 之 SQL生成技巧

 一、增 

　　1、<trim> 和<if>实现数据插入

<insert id="addInOrder" parameterType="XXX.model.InOrder">
        INSERT INTO inorder
    <trim prefix="(" suffix=")" suffixOverrides="," >
      <if test="inId != null and inId !=''" >
        inId,
      </if>
      <if test="gender != null and gender !=''" >
        gender,
      </if>
      <if test="modifiedDate != null and modifiedDate !=''" >
        modifiedDate,
    　</if>
    </trim>
    <trim prefix="values (" suffix=")" suffixOverrides="," >
      <if test="inId != null and inId !=''" >
        #{inId,jdbcType=VARCHAR},
      </if>
      <if test="gender != null and gender !=''" >
        #{gender,jdbcType=INTEGER},
      </if>
      <if test="modifiedDate != null and modifiedDate !=''" >
        #{modifiedDate,jdbcType=VARCHAR},
      </if>
    </trim>
  </insert>

　　2、新增时返回新增数据的 获取新增数据的 id值 <selectKey>

<insert id="addUser" parameterType="com.hotel3.model.User">
        <selectKey keyProperty="userId" keyColumn="userId" resultType="int" order="AFTER">
            select last_insert_id();
        </selectKey>
        INSERT INTO USER  (userName,userPassword,userType) VALUES(#{userName},#{userPassword},#{userType});
</insert>

　　　　结果：

 ==>  Preparing: INSERT INTO USER (userName,userPassword,userType) VALUES(?,?,?); 
 ==> Parameters: Not_Copy(String), 222222(String), null
 <==    Updates: 1
 ==>  Preparing: select last_insert_id(); 
 ==> Parameters: 
 <==      Total: 1

　　　　结论：select last_insert_id(); 将插入数据的主键返回到 user 对象中。

二、删

  <delete id="deleteInOrderById" parameterType="java.lang.String" >
    delete from inorder
    where inId = #{inId,jdbcType=VARCHAR}
  </delete>

三、改

　　Controller层传值代码：

　　 @PostMapping("/OverInOrder")
    @ResponseBody
    @Transactional
    public Message OverInOrder(@RequestParam(value = "InIds[]")String[] InIds, HttpSession session){

        User user= (User)session.getAttribute("loginUser");
        inOrderService.OverInOrder(InIds,"结单",user.getUserName());
       
        return new Message("", "success");
    }

　　DAO层代码：

public int OverInOrder(@Param("inIds") String[] inIds, @Param("status") String status, @Param("modifiedBy") String modifiedBy);

　　Mapper 的XML文件：

<update id="OverInOrder" parameterType="java.lang.String">
    update inorder
    <set >
      <if test="status != null and status !=''" >
        status=#{status,jdbcType=VARCHAR},
      </if>
      <if test="modifiedBy != null and modifiedBy !=''" >
        modifiedBy=#{modifiedBy,jdbcType=VARCHAR},
      </if>
      modifiedDate= SYSDATE(),
      outTime= SYSDATE()
    </set>
    WHERE inId IN
    <foreach collection="inIds" item="inId" index="index" open="(" close=")" separator=",">
      #{inId}
    </foreach>
  </update>

四、查

<select id="getInOrderAll" resultType="XXX.model.InOrder" parameterType="XXX.model.InOrder">
        select * from inorder
    <trim prefix="where 1=1" suffix=" "  suffixOverrides="," >
      <if test="inId != null and inId !=''" >
        and inId=#{inId,jdbcType=VARCHAR}
      </if>
      <if test="gender != null and gender !=''" >
        and gender=#{gender,jdbcType=INTEGER}
      </if>
      <if test="inTime != null and inTime !=''" >
        and inTime>=#{inTime,jdbcType=VARCHAR}
      </if>
    </trim>
    ORDER BY createrDate DESC;
  </select>

 　　1、模糊查询

<select id="getRoom" resultType="XXX.model.Room">
     select * from room where roomId like CONCAT('%',#{roomId},'%' )
</select>

　　　　待续。。。

　　　　

关于SQL查询的技巧还有很多，像<where>和<selectKey>等。。。

待续。。。