ibatis 中isNull, isNotNull与isEmpty, isNotEmpty区别
2011-08-10 17:49
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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 [b]cusWebAgent 时,产生的SQL语句为:[/b]
[b]select count(cus_id) from cus_customer_tbl WHERE ( CUS_CUSTOMER_TBL.CUS_WEB_FROM LIKE '%baidu%')
[/b]
[b]而当XML代码用<isNotNull > 配置时(注意他们的区别),[/b]
<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 [b]cusWebAgent 时,产生的SQL语句为:[/b]
[b][b][b]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 '%%')
[/b][/b][/b]
[b][/b]
[b][b][b]从Sql 语句就能看出他们的区别。。。。。[/b][/b][/b]
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