Query Expressions and Uniform Resource Names

Article
03/06/2017

The SQL Server Management Object (SMO) models and SQL Server PowerShell snap-ins use two types of expression strings that are similar to XPath expressions. Query expressions are strings that specify a set of criteria used to enumerate one or more objects in an object model hierarchy. A Uniform Resource Name (URN) is a specific type of query expression string that uniquely identifies a single object.

Syntax

      Object1  
      [<FilterExpression1>]/ ... /ObjectN[<FilterExpressionN>]<FilterExpression>::=  
<PropertyExpression> [and <PropertyExpression>][...n]  
  
<PropertyExpression>::=@BooleanPropertyName=true()  
 | @BooleanPropertyName=false()  
 | contains(@StringPropertyName, 'PatternString')  
  | @StringPropertyName='String'  
 | @DatePropertyName=datetime('DateString')  
 | is_null(@PropertyName)  
 | not(<PropertyExpression>)

Arguments

Object
Specifies the type of object that is represented at that node of the expression string. Each object represents a collection class from these SMO object model namespaces:

Microsoft.SqlServer.Management.Smo

Microsoft.SqlServer.Management.Smo.Agent

Microsoft.SqlServer.Management.Smo.Broker

Microsoft.SqlServer.Management.Smo.Mail

Microsoft.SqlServer.Management.Dmf

Microsoft.SqlServer.Management.Facets

Microsoft.SqlServer.Management.RegisteredServers

Microsoft.SqlServer.Management.Smo.RegSvrEnum

For example, specify Server for the ServerCollection class, Database for the DatabaseCollection class.

@PropertyName
Specifies the name of one of the properties of the class that is associated with the object specified in Object. The name of the property must be prefixed with the @ character. For example, specify @IsAnsiNull for the Database class property IsAnsiNull.

@BooleanPropertyName=true()
Enumerates all objects where the specified Boolean property is set to TRUE.

@BooleanPropertyName=false()
Enumerates all objects where the specified Boolean property is set to FALSE.

contains(@StringPropertyName, 'PatternString')
Enumerates all objects where the specified string property contains at least one occurrence of the set of characters that is specified in 'PatternString'.

@StringPropertyName='PatternString'
Enumerates all objects where the value of the specified string property is exactly the same as the character pattern that is specified in 'PatternString'.

@DatePropertyName= datetime('DateString')
Enumerates all objects where the value of the specified date property matches the date that is specified in 'DateString'. DateString must follow the format yyyy-mm-dd hh:mi:ss.mmm


yyyy	Four digit year.
mm	Two digit month (01 through 12).
dd	Two digit date (01 through 31).
hh	Two digit hour using a 24 hour clock (01 through 23).
mi	Two digit minutes (01 through 59).
ss	Two digit seconds (01 through 59).
mmm	Number of milliseconds (001 through 999).

The dates that are specified in this format can be evaluated against any date format that is stored in SQL Server.

is_null(@PropertyName)
Enumerates all objects where the specified property has a value of NULL.

not(<PropertyExpression>)
Negates the evaluation value of the PropertyExpression, enumerating all objects that do not match the condition specified in PropertyExpression. For example, not(contains(@Name, 'xyz')) enumerates all objects that do not have the string xyz in their names.

Remarks

Query expressions are strings that enumerate the nodes in an SMO model hierarchy. Each node has a filter expression that specifies the criteria for determining which objects at that node are enumerated. Query expressions are modeled on the XPath expression language. Query expressions implement a small subset of the expressions that are supported by XPath, and also have some extensions that are not found in XPath. XPath expressions are strings that specify a set of criteria that are used to enumerate one or more of the tags in an XML document. For more information about XPath, see W3C XPath Language.

Query expressions must start with an absolute reference to the Server object. Relative expressions with a leading / are not allowed. The sequence of objects that are specified in a query expression must follow the hierarchy of collection objects in the associated object model. For example, a query expression that references objects in the Microsoft.SqlServer.Management.Smo namespace must start with a Server node followed by a Database node, and so on.

If a <FilterExpression> is not specified for an object, all the objects at that node are enumerated.

Uniform Resource Names (URN)

URNs are a subset of query expressions. Each URN forms a fully-qualified reference to a single object. A typical URN uses the Name property to identify a single object at each node. For example, this URN refers to a specific column:

Server[@Name='MYCOMPUTER']/Database[@Name='AdventureWorks2012']/Table[@Name='SalesPerson' and @Schema='Sales']/Column[@Name='SalesPersonID']

Examples

A. Enumerating objects using false()

This query expression enumerates all the databases that have the AutoClose attribute set to false in the default instance on MyComputer.

Server[@Name='MYCOMPUTER']/Database[@AutoClose=false()]

B. Enumerating objects using contains

This query expression enumerates all the databases that are case-insensitive and have the character 'm' in their name.

Server[@Name='MYCOMPUTER']/Database[@CaseSensitive=false() and contains(@Name, 'm')]

C. Enumerating objects using not

This query expression enumerates all of AdventureWorks2012 tables that are not in the Production schema and contain the word History in the table name:

Server[@Name='MYCOMPUTER']/Database[@Name='AdventureWorks2012']/Table[not(@Schema='Production') and contains(@Name, 'History')]

D. Not supplying a filter expression for the final node

This query expression enumerates all the columns in the AdventureWorks2012.Sales.SalesPerson table:

Server[@Name='MYCOMPUTER']/Database[@Name='AdventureWorks2012"]/Table[@Schema='Sales' and @Name='SalesPerson']/Columns

E. Enumerating objects using datetime

This query expression enumerates all the tables that are created in the AdventureWorks2012 database at a specific time:

Server[@Name='MYCOMPUTER']/Database[@Name='AdventureWorks2012"]/Table[@CreateDate=datetime('2008-03-21 19:49:32.647')]

F. Enumerating objects using is_null

This query expression enumerates all the tables in the AdventureWorks2012 database that do not have NULL for their date last modified property:

Server[@Name='MYCOMPUTER']/Database[@Name='AdventureWorks2012"]/Table[Not(is_null(@DateLastModified))]

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