SQL
SQL was initially developed at IBM by Donald D. Chamberlin and Raymond F. Boyce after learning about the relational model from Ted Codd in the early 1970s. This version, initially called "SEQUEL" ("Structured English Query Language"), was designed to manipulate and retrieve data stored in IBM's original quasi-relational database management system, System R, which a group at IBM San Jose Research Laboratory had developed during the 1970s.
SQL PL
SQL PL stands for Structured Query Language Procedural Language and was developed by IBM as a set of commands that extend the use of SQL in the IBM DB2 (DB2 UDB Version 7) database system. It provides procedural programmability in addition to the querying commands of SQL. It is a subset of the SQL Persistent Stored Modules (SQL/PSM) language standard.