<span?style="font-family:?Arial,?Verdana,?sans-serif;?white-space:?normal;?"><strong>isNull,?isNotNull與isEmpty,?isNotEmpty區(qū)別</strong></span>??

在iBATIS中isNull用于判斷參數(shù)是否為Null，isNotNull相反

isEmpty判斷參數(shù)是否為Null或者空，滿足其中一個條件則其true
isNotEmpty相反，當(dāng)參數(shù)既不為Null也不為空是其為true

?判斷之后做相對應(yīng)的表達式操作

如下代碼：

[html]?view plaincopy

<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>??

當(dāng)之傳入?yún)?shù) cusWebForm 而不傳入?cusWebAgent 時，產(chǎn)生的SQL語句為：

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

而當(dāng)XML代碼用<isNotNull > 配置時(注意他們的區(qū)別)，

[html]?view plaincopy

<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>??

同樣 ，當(dāng)之傳入?yún)?shù) cusWebForm 而不傳入?cusWebAgent 時，產(chǎn)生的SQL語句為：

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 '%%')

從Sql 語句就能看出他們的區(qū)別。。。。。

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