XPath Query to find supplier name through an XML table

问题

I am trying to find out the cities where there is a supplier with the name of Herman. We are using XPath through Microsoft SQL Server Management Studio.

I am not a CIS major and I have no idea where to start. So that's why I'm asking for help...

I have the following table created:

CREATE TABLE Tb_Supplier(
XMLColumn XML)
GO

INSERT Tb_Supplier VALUES(
    '<SuppliersList>
      <Supplier name="Joe">
        <City>Paris</City>
        <Product name="Airplane"/>
        <Product name="Milk"/>
        <Product name="TV"/>
        <Product name="Orange"/>
     </Supplier>
      <Supplier name="Herman">
        <City>Chicago</City>
        <Product name="Orange"/>
     </Supplier>
     <Supplier name="Bernstein">
        <City>Madison</City>
        <Product name="Truck"/>
        <Product name="TV"/>
      </Supplier>
     <Supplier name="Hunter">
        <City>Wausau</City>
      </Supplier>
      <Supplier name="Mayer">
        <City>Madison</City>
      </Supplier>
      <Supplier name="Rosenfeld">
        <City>Chicago</City>
        <Product name="Computer"/>
        <Product name="Book"/>
        <Product name="Truck"/>
      </Supplier>
    </SuppliersList>');

The output is supposed to show:

<City>Chicago</City>

I got the it to work by the following:

SELECT XMLColumn.query('/SuppliersList/Supplier[@name="Herman"]/City')
FROM Tb_Suppliers

I am kind of getting the grasp of things. Currently I am having trouble how to find out the following: List the products are TV's, and are offered in Madison. Obviously the output will be since it is looking for TV.

I have this so far, I don't know what I'm doing wrong as this makes the most sense to me.

SELECT XMLColumn.query('/SuppliersList/Supplier/Product[@name="TV"]/../City[@name="Madison"]/../Product')
FROM Tb_Suppliers

回答1:

It depends whether you know, that there is exactly one "Herman" in your list. Then it's a pure call on .value() with the appropriate XPath:

SELECT XMLColumn.value(N'(/SuppliersList/Supplier[@name="Herman"]/City/text())[1]',N'nvarchar(max)') AS Herman_City
FROM Tb_Supplier

If you expect more than one, you need .nodes() to get a derived table and value() on the relative path (below the node coming from .nodes()):

SELECT AllHerman.cities.value(N'(City/text())[1]',N'nvarchar(max)') AS Herman_City
FROM Tb_Supplier
CROSS APPLY XMLColumn.nodes(N'/SuppliersList/Supplier[@name="Herman"]') AS AllHerman(cities)

回答2:

No good to tell you how to do it, but I'll give you some hints. https://msdn.microsoft.com/en-us/library/ms189075%28SQL.90%29.aspx?f=255&MSPPError=-2147217396

/* find Supplier who have truck-product */ 
    SELECT XMLColumn.query('/SuppliersList/Supplier/Product[@name="Truck"]/..') from Tb_Supplier

@ sign means "attribute". The url shows how to query element-values (a slightly different syntax than attributes).

"/" means navigate down (or sometimes up) the hierarchy.

".." means "back UP the hierarchy one level".

That should be enough to get you going.

来源：https://stackoverflow.com/questions/47664562/xpath-query-to-find-supplier-name-through-an-xml-table

标签

sql-server

sqlxml