基本的 PLpgSQL 功能

一個簡單的 PL / pgSQL 函式：

CREATE FUNCTION active_subscribers() RETURNS bigint AS $$
DECLARE
    -- variable for the following BEGIN ... END block
    subscribers integer;
BEGIN
    -- SELECT must always be used with INTO
    SELECT COUNT(user_id) INTO subscribers FROM users WHERE subscribed;
    -- function result
    RETURN subscribers;
EXCEPTION
    -- return NULL if table "users" does not exist
    WHEN undefined_table
    THEN RETURN NULL;
END;
$$ LANGUAGE plpgsql;

這可以通過 SQL 語句實現，但演示了函式的基本結構。

要執行該功能：

select active_subscribers();