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how to make field auto increment ?

Posted on 2004-04-01
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Last Modified: 2010-04-05
Im using IB expert with firebird , how can I make  An integer  field auto Increment (in details please) ?
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Question by:sraab2004
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3 Comments
 
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Trekker72 earned 20 total points
ID: 10738960
Hi, you can make do it in a Before Insert trigger for the Table like so...

CREATE TRIGGER MYTABLE_BI FOR MYTABLE
ACTIVE BEFORE INSERT POSITION 0
AS
declare variable MaxID integer;
begin
  if (new.ID is null) then begin
    select max(ID) from usertype into :MaxID;
    if (MaxID is null) then
      MaxID = 0;
    new.ID = :MaxID + 1;
  end
end

or you can create  a generator and use that...

CREATE TRIGGER MYTABLE_BI FOR MYTABLE
ACTIVE BEFORE INSERT POSITION 0
AS
begin
    new.ID = gen_id(MYTABLE_ID_Gen, 1);
end
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Author Comment

by:sraab2004
ID: 10750854
if Iwant to use generator wher should I write the code  which you gave me
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LVL 2

Expert Comment

by:Trekker72
ID: 10751629

-- first create a generator, then create a "Before Insert" trigger for the table you want the auto-inc field in.
-- The following script will set an existing field called "ID" in table "MYTABLE" to be auto-incrementing by
-- creating the generator and trigger for you.  Get yourself a program like IBExpert personal (free) to help you run scripts
-- and create meta objects, etc

CREATE GENERATOR MYTABLE_GEN_ID;
SET GENERATOR MYTABLE_GEN_ID TO 0;

Commit work;

SET TERM ^ ;

CREATE TRIGGER MYTABLE_BI FOR MYTABLE
ACTIVE BEFORE INSERT POSITION 0
AS
begin
  new.ID = gen_id(MYTABLE_ID_GEN, 1);
end

SET TERM ; ^

Commit Work;
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