insert into T values (F1 = :F1, F2 = :F2, ..., FN = :FN)

insert into T
(Id, Guid, "Time", Str, "Float", PrevId) values
(GEN_ID('G_T', 1), '{FAFB893E-8878-4709-98F4-459E7C4A59FC}', current_timestamp, Null, 198.3675483, select max(Id) from T)

insert ... set
  F1 = :F1, 
  F2 = :F2, 

-- или 

insert ... values(
  F1 = :F1, 
  F2 = :F2, 

insert into T(
  Id, 
  Guid, 
  "Time", 
  Str, 
  "Float", 
  PrevId
) values (
  GEN_ID('G_T', 1), 
  '{FAFB893E-8878-4709-98F4-459E7C4A59FC}', 
  current_timestamp, 
  Null, 
  198.3675483, 
  select max(Id) from T
)

insert into T values(
  Id = GEN_ID('G_T', 1), 
  Guid = '{FAFB893E-8878-4709-98F4-459E7C4A59FC}', 
  "Time" = current_timestamp, 
  Str = Null,
  "Float" = 198.3675483, 
  PrevId = select max(Id) from T
)

insert into T set
  Id = GEN_ID('G_T', 1), 
  Guid = '{FAFB893E-8878-4709-98F4-459E7C4A59FC}', 
  "Time" = current_timestamp, 
  Str = Null,
  "Float" = 198.3675483, 
  PrevId = select max(Id) from T

insert into T (Id, Guid, "Time", Str, "Float", PrevId)
value          (:vId,:vGuid,:vTime,:vStr,:vFloat,:vPrevId)

update T set (Str, "Float") to ('Str', "Float" * 2) where Id = 1 

merge into T
using (
  select
    next value for G_T as Id,
    '{FAFB893E-8878-4709-98F4-459E7C4A59FC}' as Guid,
    current_timestamp as "Time",
    Null as Str,
    198.3675483 as "Float",
    (select max(Id) from T) as PrevId
  from rdb$database  
) src
on T.Id = Src.Id
when not mathed then
  insert (Id, Guid, "Time", Str, "Float", PrevId) 
  values (Src.Id, Src."Time", Src.Str, Src."Float", Src.PrevId)

 for 
   select rdb$relation_id as id, rdb$relation_name as name 
   from rdb$relations 
   where rdb$view_blr is null 
   as cursor tables 
 do 
 begin 
   out_id = tables.id; 
   out_name = tables.name; 
   suspend; 
 end