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筛选工具(Select_analysis)主要用于从输入要素类或输入要素图层中提取要素(通常使用选择或结构化查询语言 (SQL) 表达式
),并将其存储于输出要素类中。
工具介绍
筛选工具是基于要素类的字段
进行要素的提取。以三调图斑为例,图斑中有一个【DLMC】字段,该字段值包括(河流水面、农村道路、公路用地、城镇村道路……),如果我们想提取出农村道路并生成单独的要素类,就可以使用【筛选】工具了。
筛选工具的路径:【分析工具】—【提取分析】—【筛选】。
筛选方法
上面举例的筛选语句【DLMC='农村道路'】是最基本的方法。更多筛选方法如下:
*
DLMC='农村道路'
结果为:筛选出【DLMC】字段值为【'农村道路'】的图斑。
*
DLMC IN ('水田','水浇地')
结果为:筛选出【DLMC】字段值为【'水田'】或【'水浇地'】的图斑。
*
DLMC NOT IN ('水田','水浇地')
结果为:筛选出【DLMC】字段值为【'水田'】和【'水浇地'】以外的图斑。
*
DLMC IS NULL
结果为:筛选出【DLMC】字段值为空值的图斑。
*
DLMC IS NOT NULL
结果为:筛选出【DLMC】字段值为非空值的图斑。
*
DLMC LIKE('%水%')
结果为:筛选出【DLMC】字段值中含有文字'水'的图斑(%代指任意字符或无字符,可被筛选出的值如:'水田','河流水域','库区水')。
*
DLMC LIKE('水%')
结果为:筛选出【DLMC】字段值中含有文字'水'(且'水'字前不得有字符)的图斑,可被筛选出的值如:'水田','水浇地')。
*
DLMC LIKE('%水')
结果为:筛选出【DLMC】字段值中含有文字'水'(且'水'字后不得有字符)的图斑,可被筛选出的值如:'库区水')。
*
DLMC LIKE('%水_')
结果为:筛选出【DLMC】字段值中含有文字'水'(且'水'字后只有一个字符)的图斑,可被筛选出的值如:'水田')。
*
DLMC='农村道路' AND Shape_Area > 100
结果为:筛选出【DLMC】字段值为【'农村道路'】,且【Shape_Area】字段值大于100的图斑。类似用法还有'OR'。
*
NOT(DLMC='农村道路' AND Shape_Area > 100)
结果为:筛选出NOT后的括号内筛选条件的相反值,和布尔运算中的【非】是一样的。
TIPS
*
【筛选】工具的目标对象是要素类或要素图层。如果对象是表,则需要用【表筛选】工具。路径位于【分析工具】—【提取分析】—【表筛选】。用法基本相同。