public IDeleteConstraintOnTableSyntax PrimaryKey(string primaryKeyName)
 {
     var expression = new DeleteConstraintExpression(ConstraintType.PrimaryKey)
                          {
                              Constraint = { ConstraintName = primaryKeyName }
                          };
     _context.Expressions.Add(expression);
     return new DeleteConstraintBuilder(expression);
 }
 public IDeleteConstraintOnTableSyntax UniqueConstraint(string constraintName)
 {
     var expression = new DeleteConstraintExpression(ConstraintType.Unique)
                          {
                              Constraint = { ConstraintName = constraintName }
                          };
     _context.Expressions.Add(expression);
     return new DeleteConstraintBuilder(expression);
 }