Oracle : How to have only one row active in a table? - oracle

Question

I have an Oracle table with a field Named Active.
This field has a unique constraint, so only one row will be marked as Active.
Is there any way in the database layer to keep only one row active when adding a new row or updating old ones ?
Example
Current State of Table
ID Active
----------------
1 yes
A new active row is added :
New State of the table
ID Active
----------------
1 No
2 Yes
The row 1 is updated with Active = Yes
ID Active
----------------
1 Yes
2 No
Of course I can not update the table using a trigger when a new row is beign inserted.
Does anyone have an idea on how to do that please ?

Answer 1

You need to call this procedure with valid values as input parameter
CREATE OR REPLACE PROCEDURE t416493.set_tab
(
p_id IN tab.id%TYPE
,p_active_flag IN tab.active%TYPE
,p_dml_type IN VARCHAR2
)
IS
CURSOR check_flag_exists
IS
SELECT id
FROM tab
WHERE active = p_active_flag;
v_id tab.id%TYPE;
v_active_flag VARCHAR2(3);
BEGIN
OPEN check_flag_exists;
FETCH check_flag_exists INTO v_id;
IF check_flag_exists%FOUND THEN
IF p_active_flag ='Yes' THEN
v_active_flag :='No';
ELSE
v_active_flag :='Yes';
END IF;
UPDATE tab
SET active = v_active_flag
WHERE id =v_id;
END IF;
CLOSE check_flag_exists;
IF p_dml_type ='INSERT' THEN
INSERT INTO tab
(id
,active
)
VALUES
(p_id
,p_active_flag
);
ELSIF p_dml_type ='UPDATE' THEN
UPDATE tab
SET active =p_active_flag
WHERE id =v_id;
END IF;
END set_tab;
You need to call your proc like this as shown below:
begin
set_tab
(
p_id =>2
,p_active_flag =>'Yes'
,p_dml_type =>'INSERT'
);
end;
/