Operations that are conceptually simple can be difficult to perform using SQL. Consider the common requirements to pivot or transpose a dataset. Each of these actions are conceptually straightforward but are complex to implement using SQL. The examples that follow are somewhat verbose, but the details are not significant. The main point is to illustrate is that, by using specialized functions outside of SQL, R makes trivial some of those operations that would otherwise require complex SQL statements. The contrast in the amount of code required is striking. The simpler approach allows you to focus attention on the scientific or business problem at hand, rather than expending energy reading documentation or laboriously testing complex statements.
I consider this where the second-order value of R comes in. The initial “wow” factor is in how easy you can plot things, and this ease of data cleansing is the next big time-saver.