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SQL (Structured Query Language) is a query language for relational databases. It allows to manipulate (extract, edit, delete, change the structure, etc.) the information, which is stored and systematized by specialized software – DBMS (database management system). Currently, SQL (for the most part in Oracle implementation) remains the most popular of the database manipulation languages.

The declarative nature of the language as compared to more traditional imperative ones, such as C# or JavaScript, make it hard even for the experienced Chief Technical Officer to hire a SQL programmer with required qualifications. The declarative programming paradigm defines the computing process by describing its logic as opposed to describing the logic of the controlling program, inherent to imperative programming. The former describes WHAT must be done, the latter – HOW it must be done. The specific implementation of database manipulation mechanisms is assigned to DBMS and varies between different vendors.

Thus, we strive to provide the seven major knowledge areas a professional SQL developer should have experience with.

A competent SQL programmer should have:

1. Solid knowledge of the database design theory, in particular, normalization, data integrity, data definition, data modelling, database indexing.
2. Knowledge of database programming technologies (writing stored procedures, functions, views).
3. Knowledge and experience with common data exchange formats (XML, JSON).
4. Knowledge of the principles and methods of database backup and recovery.
5. Knowledge of the security regulations of the target DBMS, the principles of user access levels and privileges delimitation.
6. Good knowledge of the target DBMS and its tools, knowledge of the principles and features of the installation and operation of a particular DBMS in various operating systems and environments.
7. Knowledge of ways to assess the performance of databases and optimize it, execution plans and index maintenance routines.

Upgraded versions of the basic SQL standard that most software vendors have developed over the years include a large number of advanced features, such as window functions, common table expressions and much more. Knowledge of such subtleties makes it easy to separate real professionals from novice or non-core developers. We hope this checklist will help you to make a good hiring decision.