Hiring guide for Informix-SQL Engineers

Informix-SQL Developer Hiring Guide

Informix-SQL is a relational database management system (RDBMS) developed by Informix Corporation in the 1980s. It utilizes a variant of the SQL query language, providing robust data manipulation capabilities. The software gained popularity for its speed and efficiency in handling large databases, particularly within telecommunication networks and banking systems. IBM acquired Informix Software in 2001, integrating it into their own database product line-up while continuing to develop its unique features. Today, Informix-SQL remains an important tool for businesses requiring high-performance online transaction processing.

Ask the right questions secure the right Informix-SQL talent among an increasingly shrinking pool of talent.

First 20 minutes

General Informix-SQL app knowledge and experience

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

How would you create a database in Informix?
You can create a database in Informix using the CREATE DATABASE command. The syntax is: CREATE DATABASE database_name WITH LOG;
What are the data types supported by Informix?
How would you retrieve data from a table in Informix?
You can retrieve data from a table in Informix using the SELECT statement. For example, SELECT * FROM table_name would retrieve all data from the specified table.
Describe the difference between INNER JOIN and OUTER JOIN in Informix.
An INNER JOIN returns rows when there is a match in both tables. An OUTER JOIN returns all rows from one table and the matched rows from another table. If there is no match, the result is NULL on the side of the table that doesn't have a match.
What is the purpose of the UPDATE STATISTICS statement in Informix?
The UPDATE STATISTICS statement is used to update the distribution of the values in the index and to update the optimizer's cost model, which can improve query performance.
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What you’re looking for early on

Does the candidate demonstrate a strong understanding of Informix-SQL?
Has the candidate worked with large databases before?
Is the candidate able to problem-solve and debug effectively?
Does the candidate have experience with data modeling and design?

Next 20 minutes

Specific Informix-SQL 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 handle errors in Informix?
Errors in Informix can be handled using the WHENEVER statement. This statement allows you to specify an action to be taken when an error or warning occurs.
What are the different types of indexes in Informix?
Informix supports several types of indexes including B-tree indexes, Bitmap indexes, R-tree indexes, and Extent indexes.
Describe the difference between a clustered index and a non-clustered index in Informix.
A clustered index determines the physical order of data in a table, while a non-clustered index does not alter the order of data, but creates a separate object within the table that points back to the original table rows.
How would you optimize a query in Informix?
Query optimization in Informix can be achieved through various methods such as using indexes, using the EXPLAIN statement to understand the query plan, optimizing the database schema, and using the UPDATE STATISTICS statement to update the distribution of values.
What is the role of the Informix optimizer?
The Informix optimizer is responsible for choosing the most efficient execution plan for a SQL statement. It considers factors such as the available indexes, the distribution of values, and the resources required by different execution plans.
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The ideal back-end app developer

What you’re looking to see on the Informix-SQL engineer at this point.

At this point, a skilled Informix-SQL engineer should demonstrate strong problem-solving abilities, proficiency in Informix-SQL 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 Informix-SQL.

What does the following Informix-SQL code do?
CREATE TABLE employees (id SERIAL, name CHAR(30));
This code creates a new table named 'employees' with two columns. The first column is 'id' which is of SERIAL type, and the second column is 'name' which is of CHAR type with a maximum length of 30 characters.
What will be the output of the following Informix-SQL code?
SELECT COUNT(*) FROM employees WHERE name LIKE 'A%';
This code will return the count of all rows in the 'employees' table where the 'name' starts with the letter 'A'.
What does the following Informix-SQL code do?
UPDATE employees SET name = 'John Doe' WHERE id = 1;
This code updates the 'name' field to 'John Doe' for the row in the 'employees' table where the 'id' is 1.
What will be the output of the following Informix-SQL code?
SELECT name FROM employees ORDER BY name DESC;
This code will return the 'name' of all rows in the 'employees' table, sorted in descending order.

Wrap-up questions

Final candidate for Informix-SQL 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 Informix-SQL application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

How would you implement transaction control in Informix?
Transaction control in Informix can be implemented using the BEGIN WORK, COMMIT WORK, and ROLLBACK WORK statements. These statements allow you to group a set of tasks into a single transaction.
What are the different isolation levels in Informix?
Informix supports several isolation levels including Dirty Read, Committed Read, Cursor Stability, and Repeatable Read. Each level provides a different balance between data consistency and concurrency.
Describe the difference between a stored procedure and a trigger in Informix.
A stored procedure is a precompiled collection of SQL statements and control statements stored under a name and processed as a unit. A trigger is a type of stored procedure that automatically executes in response to an event on a table.

Informix-SQL application related

Product Perfect's Informix-SQL development capabilities

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