Linq - deferred ^ immediate execution

update -- java 8 streams ...

(I feel this is a low-level but popular question...)

- if an operation returns a single value (aka aggregates) then ImmEx. ([[c# indepth]]  P281)

- if an operation returns another sequence, then defEx ([[c# indepth]]  P281)

- ToList() -- ImmEx

- sort uses ImmEx in SQL. Ditto Linq -- [[c# indepth]]  P369

- regular SQL Select with multiple output rows? Uses defEx. As you retrieve one row, all subsequent rows are subject to change.

- SQL Select with a single-row output? probably ImmEx.