使用IF / ELSE的DB2存储过程

Question

I thought this would be fairly simple but I'm still a bit stumped.

I have a stored procedure in db2 where I'm submitting a string for the variable IN_TAG_DATA . This would be something like 'Holiday', 'Weekday', 'Christmas Day', etc.

When I feed that to the proc, I want it to see if that text already exists in tag_data and if so return the tag_id . If it doesn't exist, I want it to insert it and return the newly created tag_id.

I'm a good bit of the way there but I can't quite figure out how to finally connect all the dots here.

Any help is appreciated

IN_TAG_DATA
OUT_TAG_ID

P1 : BEGIN ATOMIC

DECLARE V_TAG_ID INTEGER;

SELECT CAST(NEXT VALUE FOR SCHEMA . TAG_ID_SEQ AS INTEGER)
INTO V_TAG_ID
FROM SYSIBM . SYSDUMMY1;

IF
/*
IF EXISTS BASED ON IN_TAG_DATA, GET ID. ELSE INSERT AND RETURN created ID
*/
THEN
BEGIN 

END;
ELSE
BEGIN
INSERT INTO SCHEMA.TAGS(TAG_DATA)
VALUES(IN_TAG_DATA)
END;
END IF;

SET OUT_TAG_ID
END P1

UPDATED VERSION:

P1 : BEGIN ATOMIC

DECLARE V_TAG_ID INTEGER;

SELECT CAST(NEXT VALUE FOR SCHEMA. TAG_ID_SEQ AS INTEGER)
INTO V_TAG_ID
FROM SYSIBM . SYSDUMMY1;

BEGIN
IF
(SELECT TAG_ID FROM
SCHEMA.CAMPAIGN_TAGS
WHERE TAG_DATA=IN_TAG_DATA) IS NOT NULL
THEN
SET OUT_TAG_ID = tag_id;
ELSE

INSERT INTO SCHEMA.CAMPAIGN_TAGS(TAG_DATA)
VALUES(IN_TAG_DATA);
END IF;
END;

SET OUT_TAG_ID
END P1

Answer 1

Add this:

SET OUT_TAG_ID = (SELECT tag_id FROM
your_table
where TAG_DATA=IN_TAG_DATA)
IF 
OUT_TAG_ID  is null
THEN