where()

`where()`

For any query q, q.where(...) builds a query whose output is q's output, filtered by some condition. It's a wrapper for SQL's WHERE.

You can call q.where(condition) provided that condition is an abstract_mapper<bool> or a bool.

q's value mapper will be visible to condition.

q.where(condition) returns a query with the following characteristics:

Its value type is the same as q's
Its value mapper is identical to q's.
Its output consists of all the records that q would produce, for which condition evaluates to true. Order is preserved.