20 FetchXML Interview Questions and Answers

FetchXML is a proprietary query language used in Microsoft Dynamics CRM to fetch data. It is similar to SQL in syntax but is used to query the CRM database directly. FetchXML can be used in conjunction with JavaScript to retrieve data in CRM.

When interviewing for a position that uses Microsoft Dynamics CRM, you may be asked questions about your experience with FetchXML. It is important to be prepared to answer these questions so that you can demonstrate your knowledge and skills. In this article, we will discuss some common FetchXML interview questions and how you should answer them.

FetchXML Interview Questions and Answers

Here are 20 commonly asked FetchXML interview questions and answers to prepare you for your interview:

1. What is FetchXML?

FetchXML is a proprietary query language used in Microsoft Dynamics CRM to retrieve data. It is based on the XML standard and provides an easy way for developers to access and manipulate data from within the system. FetchXML can be used to create complex queries that include multiple entities, filters, sorting, aggregation, and other features. It also supports joins between related entities, allowing developers to easily join data from different sources. Additionally, FetchXML allows developers to use parameters to customize their queries, making it easier to reuse code and reduce development time.

2. Can you explain the basic structure of a FetchXML query?

FetchXML is a query language used to retrieve data from Microsoft Dynamics CRM. It has a basic structure that consists of four main elements: the entity, attributes, filters, and orders. The entity element defines which type of record will be retrieved, such as an account or contact. The attribute element specifies which fields should be included in the results. Filters are used to narrow down the records returned by specifying conditions that must be met. Finally, the order element allows for sorting the results based on specific criteria. All these elements can be combined to create complex queries that return exactly the desired information.

3. Is it possible to use FetchXML with Web API? If yes, then how?

Yes, it is possible to use FetchXML with Web API. The Dynamics 365 Web API supports using FetchXML to query data. This can be done by passing the FetchXML as a string parameter in the request body of an HTTP POST request. The response will contain the results of the query in either XML or JSON format depending on what was specified in the request header. Additionally, the Web API also provides methods for creating and updating records using FetchXML.

4. How can we retrieve data from multiple entities in a single FetchXML query?

FetchXML allows users to retrieve data from multiple entities in a single query. This is done by using the element, which can be used to join two or more related entities together. The element requires an attribute called ‘link-type’ that specifies how the two entities are related. Once the link type has been specified, the user can then specify the attributes of each entity they wish to retrieve. By combining multiple elements, it is possible to create complex queries that span multiple entities and return all the desired data in one result set.

5. Why should we avoid using ‘OR’ conditions in FetchXML queries?

Using ‘OR’ conditions in FetchXML queries can lead to performance issues. This is because the query must evaluate each condition separately, which can be time consuming and resource intensive. Additionally, using multiple ‘OR’ conditions can make it difficult to debug any errors that may arise from the query. It is generally better practice to use ‘AND’ conditions when possible as this will reduce the amount of resources needed for the query and make debugging easier.

6. How does the “paging cookie” attribute work in FetchXML?

The “paging cookie” attribute in FetchXML is a way to manage the amount of data that is returned from a query. It works by allowing the user to specify how many records should be returned at once, and then it will return those records along with a “cookie” which can be used to retrieve the next set of records. This allows for efficient retrieval of large amounts of data without having to make multiple requests. The paging cookie also helps reduce the amount of time needed to process the query since only the necessary records are retrieved each time.

7. How do you define a 1:N relationship in FetchXML?

A 1:N relationship in FetchXML is a type of relationship between two entities where one entity can have multiple related records from the other entity. This type of relationship is defined by using the link-entity element within the query, which allows for the retrieval of related data from both sides of the relationship. The link-entity element requires an alias and a to attribute that specifies the target entity name. Additionally, the link-type attribute must be set to either “inner” or “outer” depending on whether the related records should be included in the result set. Once these attributes are specified, the fields from both entities can be retrieved in the same query.

8. How would you sort results returned by a FetchXML query?

When sorting results returned by a FetchXML query, the orderby attribute can be used to specify the sort criteria. This attribute takes an expression that defines the field or fields to use for sorting and the direction of the sort (ascending or descending). The syntax for this expression is similar to SQL ORDER BY clauses. For example, if you wanted to sort the results by last name in ascending order, the expression would look like “lastname asc”. Additionally, multiple fields can be specified for sorting using a comma-separated list.

It is also possible to sort on related entities within a FetchXML query. To do this, the alias attribute must be used to assign an alias to each entity being queried. Then, when specifying the orderby expression, the alias should be included before the field name. For example, if you wanted to sort the results by the contact’s company name, the expression would look like “alias_contact/companyname asc”.

9. Is there any way to aggregate data while retrieving records through FetchXML? If yes, then how?

Yes, it is possible to aggregate data while retrieving records through FetchXML. This can be done by using the element within a query. The element allows for calculations such as sum, min, max, count, and average to be performed on the retrieved data. For example, if you wanted to calculate the total amount of all orders in an order table, you could use the following FetchXML:

This would return the sum of all the total amounts from the order table. It is also possible to group the results by adding a element to the query. This will allow for more complex aggregations to be performed.

10. What’s the maximum number of entities that can be retrieved in a single FetchXML query?

The maximum number of entities that can be retrieved in a single FetchXML query is 50. This limit applies to both the root entity and any related entities included in the query. It is important to note that this limit does not apply to the total number of records returned, but rather the number of distinct entities being queried. For example, if you are retrieving data from two related entities, each with 25 records, then the total number of records returned would be 50, but only two entities were actually queried.

11. What are the different types of expressions available in FetchXML?

FetchXML provides a variety of expressions that can be used to filter and sort data. These include comparison operators, logical operators, arithmetic operators, aggregate functions, and sub-queries.

Comparison operators are used to compare two values and return either true or false. Examples of comparison operators in FetchXML include equal (=), not equal (<>), greater than (>), less than (<), greater than or equal to (>=), and less than or equal to (<=).

Logical operators are used to combine multiple conditions into one expression. The three logical operators available in FetchXML are AND, OR, and NOT.

Arithmetic operators are used to perform mathematical operations on numerical values. Examples of arithmetic operators in FetchXML include addition (+), subtraction (-), multiplication (*), division (/), modulus (%), and exponentiation (^).

Aggregate functions are used to calculate summary information from a set of records. Aggregate functions available in FetchXML include count(), sum(), min(), max(), avg(), and distinct().

Sub-queries allow users to query related entities within the same FetchXML statement. Sub-queries can be used to retrieve related records, such as contacts associated with an account.

12. What do you understand about the “distinct” keyword in FetchXML?

The “distinct” keyword in FetchXML is used to ensure that the results of a query are unique. This means that if there are multiple records with the same values, only one record will be returned. The distinct keyword can be applied to any attribute or combination of attributes within an entity. It is important to note that when using the distinct keyword, all other columns must also be included in the query. This ensures that each row returned is truly unique and not just a duplicate of another row. Additionally, the distinct keyword can be combined with aggregate functions such as count() and sum(), allowing for more complex queries.

13. Is it possible to perform an inner join between two entities in FetchXML? If yes, then how?

Yes, it is possible to perform an inner join between two entities in FetchXML. This can be done by using the element within a query. The element allows for the joining of two related entities together and specifies which attributes should be used as part of the join criteria. For example, if you wanted to join the Account entity with the Contact entity on the accountid attribute, then your FetchXML would look like this:

This will return all accounts along with their associated contacts. It is also possible to specify additional conditions within the element to further refine the results.

14. What are some common mistakes made by developers when writing FetchXML queries?

One of the most common mistakes made by developers when writing FetchXML queries is not properly understanding the data structure. It is important to understand how entities are related and what fields are available in each entity before attempting to write a query. Additionally, it is important to ensure that all necessary joins are included in the query so that the desired results can be returned.

Another mistake commonly seen with FetchXML queries is using incorrect syntax or forgetting to include certain elements such as filters or orderby clauses. This can lead to unexpected results or errors being thrown. It is important to double check the syntax of the query and make sure all required elements are present.

Finally, some developers may forget to consider performance when writing their queries. If too many records are requested or if there are too many joins, this can cause the query to take an excessive amount of time to execute. It is important to keep performance in mind when writing FetchXML queries and try to limit the number of records requested and the complexity of the query.

15. What happens if you try to execute a FetchXML query on an entity which doesn’t have any records?

If a FetchXML query is executed on an entity which does not have any records, the query will return an empty result set. This means that no data will be returned from the query and it will simply display an empty table or list of results. It is important to note that this does not indicate an error in the query itself, but rather that there are simply no records available for the specified entity. In order to ensure that the query returns valid results, it is necessary to check if the entity contains any records before executing the query.

16. What are some good practices for optimizing FetchXML queries?

Good practices for optimizing FetchXML queries include limiting the number of columns returned, using filters to reduce the amount of data being retrieved, and avoiding unnecessary joins. Limiting the number of columns returned helps to ensure that only the necessary information is being requested from the server, which can help improve performance. Additionally, using filters to reduce the amount of data being retrieved can also help to optimize a query by ensuring that only relevant records are being pulled. Finally, it is important to avoid unnecessary joins as this can lead to slower query execution times.

17. Are there any limitations to what type of queries can be executed using FetchXML?

Yes, there are certain limitations to what type of queries can be executed using FetchXML. For example, FetchXML does not support the use of subqueries or joins between multiple entities. Additionally, it is limited in its ability to perform complex calculations and aggregate functions such as SUM, AVG, MIN, MAX, etc. Furthermore, FetchXML cannot be used to execute stored procedures or execute dynamic SQL statements. Finally, FetchXML does not support the use of variables within a query.

18. What are the differences between FetchXML and QueryExpression?

FetchXML and QueryExpression are both query languages used to retrieve data from Microsoft Dynamics CRM. FetchXML is a proprietary language developed by Microsoft, while QueryExpression is based on the standard Structured Query Language (SQL).

The main difference between FetchXML and QueryExpression is that FetchXML is easier to use for developers who are not familiar with SQL syntax. It also allows for more complex queries than QueryExpression, as it supports aggregate functions such as sum, min, max, count, and average. Additionally, FetchXML can be used in conjunction with other technologies such as JavaScript and Web Services, whereas QueryExpression cannot.

Another key difference between the two query languages is that FetchXML has built-in support for paging, which means that large result sets can be retrieved in smaller chunks. This makes it much more efficient when dealing with large amounts of data. On the other hand, QueryExpression does not have this feature and must be handled manually.

Finally, FetchXML provides better performance than QueryExpression due to its optimized query engine. This makes it ideal for applications that require fast response times.

19. What are the main advantages of using FetchXML over SQL statements?

FetchXML offers several advantages over SQL statements when it comes to querying data from a Microsoft Dynamics CRM system. Firstly, FetchXML is more user-friendly and easier to learn than SQL. It uses an XML syntax that is much simpler to understand and write than the complex SQL language. Secondly, FetchXML allows for greater flexibility in terms of query structure. It can be used to create queries with multiple joins, nested subqueries, and aggregate functions. Thirdly, FetchXML provides better performance than SQL as it is optimized for use with Dynamics CRM systems. Finally, FetchXML supports features such as paging, which allow users to retrieve large amounts of data without having to worry about memory or time constraints.

20. What’s your opinion on the future of FetchXML?

FetchXML is a powerful query language that has been used for many years to access data from Microsoft Dynamics CRM. It is an efficient and reliable way of retrieving data, and its popularity continues to grow as more organizations adopt the technology. As such, it is likely that FetchXML will remain a popular choice for accessing data in the future.

The development team at Microsoft is continually working on improving the capabilities of FetchXML, making it easier to use and more versatile. This means that developers can create complex queries with fewer lines of code, allowing them to quickly retrieve the data they need. Additionally, new features are being added regularly, such as support for aggregate functions and improved performance. These improvements make FetchXML even more attractive for businesses looking to access their data efficiently.

Finally, FetchXML is becoming increasingly integrated into other technologies, such as Power BI and Azure Data Factory. This allows users to easily combine data from multiple sources and analyze it in one place. With these integrations, FetchXML is becoming an even more valuable tool for businesses who want to gain insights from their data.

Overall, the future of FetchXML looks bright. Its versatility and ease of use make it an ideal choice for businesses looking to access their data quickly and effectively. With continued development and integration into other technologies, FetchXML is sure to remain a popular choice for many years to come.