InformationWeek.com: News, analysis and research for business technology professionals, plus peer-to-peer knowledge sharing. Engage with our community. According to Denver broadcaster KUSA, said goat was accompanied by several accomplices, meaning there may be an entire flock out there, just ready to ruin some place. Working with the XML Data Type in SQL Server. Not all SQL Server data types are created equal. You need jdbc4 then you can use setArray! In my case it didn't worked, as the UUID Datatype in postgres seems to still have its weak spots, but for the usual types it. Tabtight professional, free when you need it, VPN service. ![]() Just look at the XML data type. On the surface, it might seem like your run- of- the- mill type, except, of course, being geared toward XML data; but the ways in which it’s used, how its data is queried, and when and how XML columns should be indexed quickly sets the type apart from the rest of the crowd. And those differences are what matter when working within the extensible world of XML. The XML data type, in fact, lies at the heart of understanding how to store and query XML data in a SQL Server database. That’s not to suggest that all XML data should be stored with the XML type, but knowing how the type works will help you determine when to use it and how to effectively access its data. In some cases, you shouldn’t use the XML data type, but instead use large object storage- VARCHAR(MAX), NVARCHAR(MAX), or VARBINARY(MAX). For example, if you simply store your XML documents in the database and retrieve and update those documents as a whole- that is, if you never need to query or modify the individual XML components- you should consider using one of the large object data types. The same goes for XML files that you want to preserve in their original form, such as legal documents. If you need to retain an exact textual copy, use large object storage. But the rest of the time, you should consider the XML data type. ![]() The type ensures that the data is well formed according to ISO standards, and it supports fine- grained queries and modifications to specific elements and attributes within the XML. You can also index an XML column and associate its data with an XML schema collection in order to preserve its content and structure. In addition, the XML data type lets you store data that follows a structure too fluid and complex to fit easily into a relational model. However, when considering whether to use the XML data type, you should also be aware of its limitations. For instance, an XML column cannot be used as a key in an index, and a data value stored in an XML column cannot exceed 2 GB. You also cannot compare or sort data that uses the XML data type, nor can the data be used in a GROUP BY clause. For a complete description of the limitations on the XML data type, as well as other details about XML, see the topic “Implementing XML in SQL Server” in SQL Server Books Online. Creating XML Database Objects. SQL Server lets you assign the XML data type to columns, variables, or parameters and store in any of these objects either XML documents or fragments. The data is considered a document if it has a single top- level element. Otherwise it falls under the category of fragment. NOTE: You can also assign the XML data type to values returned by a function. However, function return values usually require XML components more complex than what we’ll cover in this article. For this reason, functions will be covered in a later article, after those XML components have been discussed. When you assign the XML data type to a column, variable, or parameter, you can optionally associate an XML schema collection with the object, thus ensuring that data within that object conforms to schema specifications. In such cases, the object is referred to as typed. An XML object with no associated schema collection is considered untyped. Creating Untyped XML Objects. An untyped XML object still requires that the data be well formed according to ISO standards; however, the data is not bound to an XML schema collection. You should choose untyped XML (the default) if you don’t have a schema to associate with the data or you don’t want to adhere to the constraints imposed by a schema. For instance, you might have a workable schema but might also need to store nonconforming fragments temporarily in the XML column. To create an XML object in your database, you simply specify the XML data type as you would any other type. For instance, the following Transact- SQL code creates the Resumes tables, inserts data into the table, and then retrieves data from that table: 1. USEAdventure. Works. R2; GOIFOBJECT_ID('dbo. Resumes')ISNOTNULLDROPTABLEdbo. Resumes; GOCREATETABLEdbo. Resumes( Candidate. IDINTIDENTITYPRIMARYKEY, Candidate. Resume. XML); INSERTINTOResumes (Candidate. Resume)SELECTResume. FROMHuman. Resources. Job. Candidate; SELECT*FROMResumes; Notice that the table includes the Candidate. Resume column, which is configured with the XML data type. Because this is an untyped column, you don’t have to specific any other parameters related to the XML. You can, of course, specify the nullability or other column properties, but XML is all you need to include to create an XML column. NOTE: I created the examples in this article within the Adventure. Works. 20. 08. R2 database on a local instance of SQL Server 2. R2. When I ran the example above, the INSERT statement added 1. Job. Candidate table into the Resumes table. I verified that the new rows had been added by running the SELECT statement, which also returned 1. Each returned row included an XML value in the Candidate. Resume column. (Note that, in SQL Server Management Studio, you can click an XML value to open a window that displays the entire XML document or fragment.)Because the Candidate. Resume column is untyped XML, the inserted data did not have to conform to a specific schema collection; however, the data still had to conform to the ISO standards that govern XML. You can create an XML variable just as easily as you can create a column. In the following example, I declare the @Resume variable and set its value equal to the XML data retrieved from the Resumes table for candidate 1: DECLARE@resume. XML; SELECT@resume=Candidate. Resume. FROMdbo. Resumes. WHERECandidate. ID=1; SELECT@resume. ASResume; As with the column definition, I simply specified the XML data type when I declared the variable. Again, the XML is untyped, which means that the data does not have to conform to a schema collection. When I ran the SELECT statement after declaring and setting the variable, it returned only a single value: the XML data I had inserted into the Resumes table for that candidate. As mentioned above, you can also assign the XML data type to a parameter. In the next example, I create a stored procedure that’s defined with an XML input parameter: USEAdventure. Works. 20. 08. R2; GOIFOBJECT_ID ('dbo. Add. Resume','P')ISNOTNULLDROPPROCEDUREdbo. Add. Resume; GOCREATEPROCEDUREAdd. Resume @resume. XMLAS INSERTINTOResumes (Candidate. Resume) VALUES(@Resume); GO Notice that the @Resume parameter is untyped XML. The stored procedure uses that parameter to insert data into the Resumes table. After I created the procedure, I declared an XML variable named @Resume. XML data to the variable. I retrieved the data from the Job. Candidate table.) I then called the @Resume. I executed the stored procedure, as shown in the following example: DECLARE@resume. XML; SELECT@resume. Resume. FROMHuman. Resources. Job. Candidate. WHEREJob. Candidate. ID=4; EXECAdd. Resume@resume. SELECT*FROMResumes; The stored procedure adds another row to the Resumes table. The row includes the XML data that I assigned to the @Resume. When I ran the SELECT statement this time, it returned 1. Creating Typed XML Objects. If you have a schema collection available to associate with your XML data, you should consider using that collection. Typed XML has several advantages over untyped. To begin with, it provides another level of validation. Not only must the XML data be well formed (based on ISO standards), but it must also conform to the validation constraints and data type specifications defined by the schema. For example, the type information enforces more precise semantics on the XML values. In addition, storage and queries are better optimized than on an untyped column. However, before you can associate an XML object with a particularly schema, that schema must be registered in the database in which you’ll be defining the object. Only then can you reference that schema when you create your XML object. NOTE: Registering schema collections is beyond the scope of this article. You can find details about how to register a collection in SQL Server Books Online, in the topic “CREATE XML SCHEMA COLLECTION (Transact- SQL).”Once you’ve registered your schema collection, you can define your XML column, variable, or parameter. To do so, you must include the name of the collection in parenthesis after the XML data type name.
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