title: can check constraints be violated by writing to subquery tables?
body: <p>With Firebird, if I have a check constrained by a subquery to another table, and I write to the table in the subquery that would violate the check, what fails, if anything?</p>
  
  <p>If nothing fails, will the constraint be violated on the next read from the table with the check constraint?  If not, what does Firebird do to prevent the constraint from being violated on read?</p>
  
  <p><strong>Example</strong></p>
  
  <p><code>table_a</code> has a check constraint on <code>column_a_table_a</code> that should be <code>&lt; SUM(column_a_table_b) FROM table_b</code>.</p>