[英]Population data xquery
对于下面的XML数据,我试图在此处显示输出:即,我想查看人口大于20000的国家/地区的名称,条件是显示的城市数应仅针对人口更多的城市。超过3500。此外,对于某些国家/地区,该城市位于省内。
<result>
<country name="B">
<num_cities>3</num_cities>
</country>
<country name="C">
<num_cities>2</num_cities>
</country>
</result>
---------------------------这是XML数据------------------ ----
<country id="1" name="A" population="12000">
<name>A</name>
<city id="c1" country="1">
<name>T1</name>
<population>5000</population>
</city>
<city id="c2" country="1">
<name>T2</name>
<population>3000</population>
</city>
<city id="c3" country="1">
<name>T3</name>
<population>4000</population>
</city>
</country>
<country id="3" name="B" population="80000">
<name>B</name>
<city id="c4" country="2">
<name>T4</name>
<population>6000</population>
</city>
<city id="c5" country="2">
<name>T5</name>
<population>2000</population>
</city>
<city id="c6" country="2">
<name>T6</name>
<population>60000</population>
</city>
<city id="c7" country="2">
<name>T7</name>
<population>12000</population>
</city>
</country>
<country id="3" name="C" population="68000">
<name>C</name>
<province>P1</province>
<city id="c8" country="3">
<name>T8</name>
<population>51000</population>
</city>
<city id="c9" country="3">
<name>T9</name>
<population>3000</population>
</city>
<city id="c10" country="3">
<name>T10</name>
<population>14000</population>
</city>
</country>
我写了这个xquery,但我不知道如何排除人口> 3500的城市。我也可能没有正确编写代码...请协助。
for $c in doc("abc")//country
let $city:= count($c/city/name)
let $citypr:= count($c/province/city/name)
where $c/@population>1000000
return
<result>
<country name='{data($c/name) }'></country>
<num_of_cities>
{
if (exists ($c/city/name)) then
$city
else
$citypr
}
</num_of_cities>
</result>
一些提示:
在检索内容的说明符中,不要理会可以更早过滤掉where
子句的地方。
如果您只希望有一个<result>
,而不是每个数据一个,则需要在FLWOR表达式之前启动它。 无论您“退货”如何,每件商品都会退货一次。
这是更接近的示例:
<result>{
for $large-country in doc("abc")//country[@population > 20000]
let $large-cities := $country/city[population > 3500]
return
<country name="{$large-country/@name}">
<num_cities>{count($large-cities)}</num_cities>
</country>
}</result>
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