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  • ibatis 中isNull, isNotNull与isEmpty, isNotEmpty区别

    在iBATIS中isNull用于判断参数是否为Null,isNotNull相反

    isEmpty判断参数是否为Null或者空,满足其中一个条件则其true
    isNotEmpty相反,当参数既不为Null也不为空是其为true

     判断之后做相对应的表达式操作


    如下代码:

         <select id="getCustomerRegNum" resultClass="int" parameterClass="QueryCustomerCondition">
                select count(cus_id) from cus_customer_tbl 
                <dynamic prepend="WHERE">
                    <isNotEmpty prepend="AND" property="cusWebFrom">
                        ( CUS_CUSTOMER_TBL.CUS_WEB_FROM LIKE '%$cusWebFrom$%')
                    </isNotEmpty>
                    <isNotEmpty prepend="AND" property="cusWebAgent">
                        ( CUS_CUSTOMER_TBL.CUS_WEB_AGENT LIKE '%$cusWebAgent$%')
                    </isNotEmpty>
                </dynamic>
         </select>

    当之传入参数 cusWebForm 而不传入 cusWebAgent 时,产生的SQL语句为:

    select count(cus_id) from cus_customer_tbl    WHERE      ( CUS_CUSTOMER_TBL.CUS_WEB_FROM LIKE '%baidu%')

    而当XML代码用<isNotNull > 配置时(注意他们的区别):

         <select id="getCustomerRegNum" resultClass="int" parameterClass="QueryCustomerCondition">
                select count(cus_id) from cus_customer_tbl 
                <dynamic prepend="WHERE">
                    <isNotNull prepend="AND" property="cusWebFrom">
                        ( CUS_CUSTOMER_TBL.CUS_WEB_FROM LIKE '%$cusWebFrom$%')
                    </isNotNull>
                    <isNotNull prepend="AND" property="cusWebAgent">
                        ( CUS_CUSTOMER_TBL.CUS_WEB_AGENT LIKE '%$cusWebAgent$%')
                    </isNotNull>
                </dynamic>
         </select>

    同样 ,当之传入参数 cusWebForm 而不传入 cusWebAgent 时,产生的SQL语句为:

    select count(cus_id) from cus_customer_tbl     WHERE     ( CUS_CUSTOMER_TBL.CUS_WEB_FROM LIKE '%baidu%')      AND        (CUS_CUSTOMER_TBL.CUS_WEB_AGENT LIKE '%%')


    从Sql 语句就能看出他们的区别。。。。。

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  • 原文地址:https://www.cnblogs.com/longshiyVip/p/5049485.html
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