As the question title implies, the following is a simple sentence written in plain English.
- Schemas are changed infrequently, if at all.
Where schema is a special term used in Database Management System - DBMS implying the overall logical structure of a database or simply say the overall design of a database. A database can be thought of as a collection of well-structured, well-organized and interrelated tables that may contain a huge collection of related information in the form of rows (or records - an older term) and columns (or fields - an older term) in each of the tables.
The terms row, column and table in DBMS are especially designated by the terms entity, attribute and entity class or entity set respectively. An entity class in DBMS is also called a relation in very special contexts (for example, normalization).
The terms record and field were especially used before the advent of DBMSs.
The meaning of the main clause is obvious but I really don't get the meaning of the subordinate clause or if-clause. It appears that something is deliberately disguised in the if-clause for some specific reasons.
What does if at all mean in this sentence?