Querying in Azure Cognitive Search makes use of a URL-encoded string represented in OData syntax. This means that you build a query using logical operators, filter expressions, and certain predefined keywords. Below is a simple example of a search query:
search=HotelName:Marriot&$count=true&$filter=BaseRate ge 150 and BaseRate le 300
In this query, ‘search’ signifies keywords or phrases to look for. The ‘filter’ operator helps limit the results to documents matching the condition, where ‘BaseRate’ is greater than or equal (ge) to 150, and less than or equal (le) to 300. The ‘$count’ parameter is used to get the total count of matched documents.
Sorting Query Results
Sorting influences the order in which search results are returned. By default, documents in Azure Cognitive Search are not ordered. However, you can add the ‘orderby’ clause in a search query to sort results on a specified field.
search=HotelName:Marriot&$orderby=BaseRate asc
In the above query, results are sorted based on ‘BaseRate’ in ascending (asc) order. You can specify multiple fields for sorting and use the ‘desc’ keyword to sort in descending order.
Filtering Results
The process of viewing only specified documents from a collection is termed filtering. The ‘filter’ clause in Azure Cognitive Search needs a Boolean expression to isolate the documents you want. You use Logical Operators (and, or, not) and Comparison Operators (eq, ne, gt, lt, ge, le).
$filter=Rating eq 5 and BaseRate lt 200
The above query filters out documents with a ‘Rating’ of 5 and a ‘BaseRate’ less than 200.
Using Wildcards
For added flexibility, Azure Cognitive Search supports the use of wildcards in queries. A wildcard is a character that stands in for other characters. There are two main wildcard characters.
- Asterisk(*): This is the most commonly used wildcard character. It stands in for any number of characters. For instance, ‘*t’, ‘t*’, ‘*t*’, matches to any string containing ‘t’.
- Question mark(?): This represents exactly one character. For example, ‘t?st’ matches ‘test’ or ‘tast’, but not ‘tst’ or ‘ttoast’.
search=HotelName:Marri*
This query will return hotels with names that start with ‘Marri’. Note that wildcards only work with prefix matching (‘field*:’), not midpoint, or suffix matching.
This guide provides an introduction to querying an index, including syntax, sorting, filtering, and wildcards in the context of the ‘AI-102 Designing and Implementing a Microsoft Azure AI Solution’ exam. For more detailed lessons, the Microsoft Azure AI documentation offers comprehensive tutorials and explanations.
Practice Test
True/False: In Azure AI, an index is a physical entity that you can interact with.
- True
- False
Answer: True.
Explanation: In Azure AI, indexes are physical entities that you can manage on your own. You can create, delete, reload, and clone them, or adjust their schema.
Which of the following structures can be used to improve the performance and manageability of data retrieval in Azure AI?
- a. Indexes
- b. Tables
- c. Columns
- d. Frames
Answer: a. Indexes.
Explanation: Indexes provide a way to faster access to rows in a table, improve the performance of the data retrieval, enhance the efficiency and manageability of queries.
What does the Azure search “filter” function do?
- a. speeds up data retrieval
- b. modifies data
- c. restricts the results set
- d. increases data storage
Answer: c. restricts the results set.
Explanation: The filter function in Azure search is used to restrict the results set by omitting documents that don’t match the specified criteria.
True/False: Wildcards are special characters that represent unknown or replaceable characters that you can use in a query.
- True
- False
Answer: True.
Explanation: Wildcards are special characters which stand for other characters or groups of characters in search queries that make the search more flexible.
True/False: Sort command in a query helps to display the results in ascending or descending order.
- True
- False
Answer: True.
Explanation: Sorting is a feature of querying an index that allows you to organize and display your query output in either ascending or descending order.
Can you alter the schema of a non-empty index in Azure AI?
- a. Yes, always
- b. Yes, but only when the index is offline
- c. No, you can’t alter a non-empty index
- d. No, but you can clone and modify it
Answer: d. No, but you can clone and modify it.
Explanation: Azure AI doesn’t allow you to alter the schema of a non-empty index. But you can clone the index and then modify its schema.
What does the syntax of a query include?
- a. Statements
- b. Expressions
- c. Clauses
- d. All of the above
Answer: d. All of the above
Explanation: The syntax of a query includes statements (for performing actions), expressions (for manipulating data) and clauses (for specifying conditions or scope).
True/False: Wildcards can be used at the beginning of a search term
- True
- False
Answer: False
Explanation: In Azure Search, leading wildcards are not supported, which means wildcards can’t be used at the beginning of a word.
What is the default order sorting in Azure AI?
- a. Ascending
- b. Descending
- c. Random
- d. No sorting applied by default
Answer: a. Ascending.
Explanation: By default, Azure AI sorts results in ascending order. However, you can explicitly specify the sorting order in your query.
True/False: Azure AI supports only AND, OR logical operators for filtering.
- True
- False
Answer: False
Explanation: Azure AI supports AND, OR, and NOT logical operators for filtering. It allows you to specify more complex conditions for filtering your query.
Interview Questions
What is the syntax for querying an index in Microsoft Azure?
The syntax for querying an index involves specifying the search service, the index to query, the API version, and the search parameters. For instance, “https://[search service name].search.windows.net/indexes/[index name]/docs?api-version=2019-05-06&[search parameters]”
What is Azure Search sort syntax used for?
The Azure Search sort syntax, “&$orderby=[field name] asc/desc”, is used to sort the results of an index query in ascending or descending order according to a specific field in the index.
How do you specify a filter when querying an index in Microsoft Azure?
You can specify a filter when querying an index by using the “$filter” parameter in your query. For instance, “$filter=field eq ‘value’” only includes results where the ‘field’ is equal to ‘value’.
How can you search for multiple terms within an index in Azure?
You can search for multiple terms within an index by separating each term with a space in your query. Azure will return documents that contain any of the specified terms.
What role do wildcards play when querying an index in Azure?
Wildcards, indicated by the ‘*’ or ‘?’ symbols, are used in Azure queries to allow for greater flexibility in matching terms within the index. The ‘*’ can represent any sequence of characters, while the ‘?’ represents any single character.
Can you use wildcard characters in Azure’s “$filter” expressions?
No, wildcard characters cannot be used in Azure’s “$filter” expressions. They are only valid in “search=” expressions.
What is the purpose of the “$top” parameter while querying an index in Azure?
The “$top” parameter is used to limit the number of search results returned by Azure. For instance, “$top=5” will return the top five results.
What is the use of “$count” in Azure Search?
The “$count” parameter is used to retrieve the total count of the results of a query in Azure search. By setting “$count=true”, the total count of matching results will be included in the response.
How can the “$skip” parameter be used in Azure index queries?
The “$skip” parameter can be used to skip over a specified number of results in the index query. It’s mainly used when implementing data paging in the search solution.
How do you combine multiple filter expressions while querying an index in Azure?
Multiple filter expressions can be combined by using the logical operators “and” or “or”. For instance, “$filter=field1 eq ‘value1’ and field2 eq ‘value2′” will only return results where both conditions are met.
Can we use the wildcard character in the beginning of a term in Azure Search?
No, the wildcard character cannot be used at the beginning of a term in Azure Search. It can only be used at the end of a term.
How is full-text search enabled in the Azure search?
Full-text search in Azure is enabled by default for all string fields when creating an index. It allows you to use full-text search queries that use natural language techniques.
How is score influencing achieved in Azure Search?
Score influencing in Azure Search can be achieved using the scoring profiles. Scoring profiles provide fine-grained control over how search scores are calculated by enabling the use of functions that boost certain matches.
How can highlighting be enabled in Azure Search?
Highlighting can be enabled in Azure Search using the “highlight” parameter in the query, which receives a comma-separated list of one or more fields to be highlighted.
Can we sort on multiple fields in Azure Search?
Yes, we can sort on multiple fields in Azure Search. This is achieved by providing multiple fields separated by a comma in the “$orderby” clause, e.g., “$orderby=field1 asc, field2 desc”.
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