The most common Procedural Language-Structured Query Language (PL-SQL) interview questions are designed to reveal the depth of knowledge that the candidate has about the subject. For this reason, the opening questions are typically broad in scope and relate to subjects such as the differences between the industry standard American National Standards Institute (ANSI) SQL and PL-SQL. Likewise, a candidate might be asked to discuss the advantages and disadvantages of using stored procedures rather than a client-side solution. Further questions drill down to the specifics of the language.
There are some fundamental concepts that will almost always appear in PL-SQL interview questions. Some examples are: What is a procedure? What is a package? How and when should you implement triggers? How do you handle exceptions in PL-SQL? Anybody who has been working with PL-SQL, even at a basic level, should be very familiar with these concepts.
More direct and specific PL-SQL interview questions attempt to reveal a deeper knowledge and experience with common issues that face the PL-SQL developer. How do you handle NULL values? What is the difference between a NULL value and a value of zero? What are the most common data types used in PL-SQL? What is a BLOB? When is it appropriate to use a type of varchar? The handling of data types is critical to the integrity of data and the overall performance of a system, so these subjects will be foremost in the mind of a manager.
Another favorite topic for PL-SQL interview questions is cursors. The use of cursors in PL-SQL is fundamental to all data retrieval and manipulation, so many PL-SQL interview questions are centered around this subject. Some typical questions that might be encountered are: What keyword identifies the column-type of a cursor field? How do you handle a situation where a SELECT cursor returns no data? How often should you perform a commit when you are inserting records? What issues might you face regarding concurrent access on a table? What is a deadlock and what is the most efficient manner in which it can be resolved?
PL-SQL is a very rich programming language, so it is rare that somebody will know every single detail. Some of these common interview questions can reveal the knowledge and experience that a candidate has acquired. The broad discussion-type questions are a real opportunity for a candidate to exhibit mastery of the features and complexity of PL-SQL.