How is social constructivism associated with scientific realism, anti-realism, and irrealism?

Social constructivism is a social theory of knowledge that
applies the general philosophical constructionism of a culture into a social setting. 
When this knowledge is absorbed by the members of a culture, it is a shared common
knowledge by the members of that culture, generally held to be
true.

Social constructivism associates very well with
scientific realism.  Scientific realism is a direct attempt by the science community
at-large to explain the things occurring in the physical world.  The attainment of this
body of knowledge, of how and why things work, are passed on in our homes, our schools,
and generally regarded to be true.

There are always
multiple ways of explaining things and this is where the anti-realists come in.  They
believe it would be a serious mistake to make the claim that all the answers we come up
with as realists are correct.  At one time, the Earth was believed to be flat; how true
is that belief today?

Last, but not least, the metaphysical
irrealistic philosophy tends to combine the "best of both worlds" by asserting each is a
world version.  Parts of the knowledge base of each are generally acceptable while parts
are not so.  The position might be summarized in colloquial terms as "Keep the part that
works and let's fix the part that doesn't."