mybatis的动态sql之if test的使用说明

<select id="getMaxDepartId" parameterType="java.lang.String" resultType="java.lang.String">
    SELECT MAX(DEPART_ID) FROM T_P_DEPART 
    <where>
      <if test="_parameter!=null and _parameter!=''"> 
        AND DEPART_PID = #{departId,jdbcType=VARCHAR} 
      </if>
      <if test="_parameter==null or _parameter==''"> 
        AND DEPART_PID IS NULL
      </if>
    </where>
  </select>

<select id="findShopByName" parameterType="ShopVo" resultType="ShopCustomer">
  select * from shop 
  <where>
      <if test="shopCustomer.shopname!=null and shopCustomer.shopname!=''">
        shop.shopname like '%${shopCustomer.shopname}%'
      </if>
      <if test="shopCustomer.shopname==null or shopCustomer.shopname==''"> 
        AND shop.shopname is null
      </if>
  </where>
</select>

<if test="title != null">
  AND title like #{title}
</if>

<if test="title != null and title != ''" >
  AND title like #{title}
</if>

<update id="updateObject" parameterType="*.*.Object" >
update table
 <set>
  <if test="Object.fullName == null or Object.fullName ==''">
  full_name = null,
  </if>
  <if test="Object.fullName != null and Object.fullName !=''">
  full_name = #{companyOrg.fullName},
  </if>
  <if test="Object.level == null or Object.level ==''">
  level = null,
  </if>
  <if test="Object.level == 0 ">
  level = null,
  </if>
  <if test="Object.level != null and Object.level !='' and Object.level != 0 ">
  level = #{companyOrg.level},
  </if>
 
 </set>
 where 1=1 and id =#{companyOrg.id}
</update>