It is impossible to think of PL/SQL without also thinking about SQL operations because the main purpose of PL/SQL is to provide the fastest and most efficient way of extending the relational database environment into the realm of procedural logic. The most important thing to remember is that SQL and PL/SQL are completely separate languages, each with its own strengths and weaknesses. SQL and PL/SQL have different memory structures, optimization mechanisms, etc. The critical difference between them is that PL/SQL is a procedural language, whereas SQL is a declarative, set-based language. This fundamental difference between the two languages means that you cannot effectively utilize SQL and PL/SQL together unless you stop thinking exclusively in terms “line-by-line” and “row-by-row”.