Select 1 into variable postgresql? - postgresql

Question

I have this select statement inside a trigger procedure:
SELECT 1 FROM some_table WHERE "user_id" = new."user_id"
AND created >= now()::date;
How can i store result in a variable and reuse it in IF statement like this:
IF NOT EXISTS (var_name) THEN ...;
procedure (for now i have select right in IF statement, but i want it separately)
CREATE OR REPLACE FUNCTION add_row() RETURNS TRIGGER AS $$
BEGIN
//need to check if row was created around today
IF NOT EXISTS (SELECT 1 FROM some_table WHERE "user_id" = new."user_id"
AND created >= now()::date) THEN
INSERT INTO another_table VALUES(1, 2, 3);
END IF;
END;
$$ LANGUAGE plpgsql;

Answer 1

To store the result of a query into a variable, you need to declare a variable. Then you can use select .. into .. to store the result. But I would use a boolean and an exists condition for this purpose.
CREATE OR REPLACE FUNCTION add_row()
RETURNS TRIGGER
AS $$
declare
l_row_exists boolean;
BEGIN
select exists (SELECT *
FROM some_table
WHERE user_id = new.user_id
AND created >= current_date)
into l_row_exists;
IF NOT l_row_exists THEN
INSERT INTO another_table (col1, col2, col3)
VALUES(1, 2, 3);
END IF;
END;
$$ LANGUAGE plpgsql;
However, you don't really need an IF statement to begin with. You can simplify this to a single INSERT statement:
INSERT INTO another_table (col1, col2, col3)
SELECT 1,2,3
WHERE NOT EXISTS (SELECT *
FROM some_table
WHERE user_id = new.user_id
AND created >= current_date);