Hiring guide for Transact-SQL Query (TSQL Query) Engineers

Transact-SQL Query (TSQL Query) Developer Hiring Guide

Transact-SQL Query (TSQL Query) is a proprietary programming language developed by Microsoft. It was first introduced in 1989 as an extension to the Structured Query Language (SQL) for interacting with relational databases. TSQL incorporates various features such as procedural programming, local variables, and support for error and exception handling. This language is primarily used to manage and manipulate data in Microsoft SQL Server. Its versatility and robustness have made it a standard tool among database administrators and developers worldwide.

Ask the right questions secure the right Transact-SQL Query (TSQL Query) talent among an increasingly shrinking pool of talent.

First 20 minutes

General Transact-SQL Query (TSQL Query) app knowledge and experience

The first 20 minutes of the interview should seek to understand the candidate's general background in Transact-SQL Query (TSQL Query) application development, including their experience with various programming languages, databases, and their approach to designing scalable and maintainable systems.

What is the purpose of the SELECT statement in TSQL?
The SELECT statement is used to select data from a database. The data returned is stored in a result table, called the result-set.
How would you use the WHERE clause in a TSQL query?
The WHERE clause is used to filter records. It is used to extract only those records that fulfill a specified condition.
What are JOINS in TSQL and why are they used?
JOINS are used to combine rows from two or more tables, based on a related column between them. There are different types of joins: INNER JOIN, LEFT (OUTER) JOIN, RIGHT (OUTER) JOIN, and FULL (OUTER) JOIN.
Describe the difference between UNION and UNION ALL in TSQL.
UNION is used to combine the result-set of two or more SELECT statements, but it removes duplicate rows. UNION ALL does the same, but it does not remove duplicate rows.
What is the purpose of the GROUP BY statement in TSQL?
The GROUP BY statement is used in collaboration with the aggregate functions to group the result-set by one or more columns.
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What you’re looking for early on

Does the candidate have a strong understanding of TSQL syntax and query optimization?
Has the candidate demonstrated experience with database design and data modeling?
Is the candidate familiar with SQL Server Management Studio (SSMS) and other relevant tools?
Can the candidate debug and solve database issues?

Next 20 minutes

Specific Transact-SQL Query (TSQL Query) development questions

The next 20 minutes of the interview should focus on the candidate's expertise with specific backend frameworks, their understanding of RESTful APIs, and their experience in handling data storage and retrieval efficiently.

How would you use the HAVING clause in a TSQL query?
The HAVING clause was added to SQL because the WHERE keyword could not be used with aggregate functions. It is typically used with the GROUP BY clause to filter group rows that do not fulfill a specified condition.
What are stored procedures in TSQL and why are they used?
Stored procedures are prepared SQL codes that you can save, so the code can be reused over and over again. They can be used to perform actions such as updating data on a database, or returning data.
Describe the difference between a primary key and a foreign key in TSQL.
A primary key is a field in a table which uniquely identifies each row/record in a database table. Primary keys must contain unique values. A foreign key is a field (or collection of fields) in one table, that refers to the primary key in another table.
What is the purpose of the ALTER TABLE statement in TSQL?
The ALTER TABLE statement is used to add, delete/drop or modify columns in an existing table. It is also used to add and drop various constraints on an existing table.
How would you use the CASE statement in a TSQL query?
The CASE statement goes through conditions and returns a value when the first condition is met. Once a condition is true, it will stop reading and return the result. If no conditions are true, it returns the value in the ELSE clause.
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The ideal back-end app developer

What you’re looking to see on the Transact-SQL Query (TSQL Query) engineer at this point.

At this point, a skilled Transact-SQL Query (TSQL Query) engineer should demonstrate strong problem-solving abilities, proficiency in Transact-SQL Query (TSQL Query) programming language, and knowledge of software development methodologies. Red flags include lack of hands-on experience, inability to articulate complex concepts, or unfamiliarity with standard coding practices.

Digging deeper

Code questions

These will help you see the candidate's real-world development capabilities with Transact-SQL Query (TSQL Query).

What does the following simple T-SQL query do?
SELECT * FROM Employees WHERE EmployeeID = 123;
This T-SQL query selects all columns of the row from the 'Employees' table where the 'EmployeeID' is 123.
What does the following T-SQL query do?
UPDATE Products SET Price = Price * 1.10 WHERE Category = 'Electronics';
This TSQL query updates the 'Price' column in the 'Products' table, increasing it by 10% for all rows where the 'Category' is 'Electronics'.
What will be the output of the following T-SQL query that involves array or collection manipulation?
SELECT STRING_AGG(Name, ', ') FROM Employees WHERE Department = 'Sales';
This T-SQL query will return a single string that concatenates the 'Name' of all employees in the 'Sales' department, separated by commas.
What does the following T-SQL query do, which is related to concurrency?
BEGIN TRAN; UPDATE Employees SET Salary = Salary * 1.05 WHERE Department = 'Sales'; COMMIT;
This T-SQL query starts a transaction, updates the 'Salary' column in the 'Employees' table, increasing it by 5% for all rows where the 'Department' is 'Sales', and then commits the transaction. This ensures atomicity of the operation.

Wrap-up questions

Final candidate for Transact-SQL Query (TSQL Query) Developer role questions

The final few questions should evaluate the candidate's teamwork, communication, and problem-solving skills. Additionally, assess their knowledge of microservices architecture, serverless computing, and how they handle Transact-SQL Query (TSQL Query) application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

What are indexes in TSQL and why are they used?
An index in a database is used to speed up the performance of queries. It makes the query-fetching operation faster. Indexes can be created using one or more columns, providing the basis for both rapid random lookups and efficient ordering of access to records.
Describe the difference between a clustered and a non-clustered index in TSQL.
A clustered index determines the physical order of data in a table, there can be only one clustered index per table. Non-clustered indexes, on the other hand, do not alter the physical order of data in the table. They maintain a separate object within the table called a B-tree to hold the index data, so there can be multiple non-clustered indexes on a single table.
What is the purpose of the UPDATE statement in TSQL?
The UPDATE statement is used to modify the existing records in a table.

Transact-SQL Query (TSQL Query) application related

Product Perfect's Transact-SQL Query (TSQL Query) development capabilities

Beyond hiring for your Transact-SQL Query (TSQL Query) engineering team, you may be in the market for additional help. Product Perfect provides seasoned expertise in Transact-SQL Query (TSQL Query) projects, and can engage in multiple capacities.