render method
Renders this clause to SQL text, recording any bind values on context.
context is the entire context a clause is given: use
RenderContext.escapeName for identifiers and RenderContext.param
for values.
Return an empty string to render nothing, which is how an optional clause
(such as a WHERE with no filter) drops itself from the statement.
Implementation
@override
String render(RenderContext context) =>
'SET ${UpdateSetClause(assignments).render(context)}';