PostgreSQL数据库添加更新只用一个函数insertupdate

--建表
  CREATE TABLE user_friend
(
  uf_id serial NOT NULL,
  uf_userid integer NOT NULL,
  uf_friendlist character varying(1000),
  uf_created timestamp without time zone DEFAULT now(),
  uf_count integer,
  uf_listname character varying(1000),
  CONSTRAINT pk_user_friend PRIMARY KEY (uf_id)
);
--新建一个函数，用于用户添加和插入数据
CREATE OR REPLACE FUNCTION add_friend(userid INT, friend_userid INT, friend_name character varying) RETURNS INT AS
$$
BEGIN
    LOOP
        -- first try to update the key
        UPDATE user_friend set uf_friendlist = replace(uf_friendlist, ','||friend_userid||',', ',')||friend_userid||',', uf_listname = replace(uf_listname, ','||friend_name||',', ',')||friend_name||',',uf_count = length(uf_friendlist) - length(REPLACE(uf_friendlist, ',', '')) - 1 where uf_userid=userid;
        IF found THEN
            RETURN 1;
        END IF;
                
        BEGIN
            INSERT INTO user_friend(uf_userid,uf_friendlist,uf_count,uf_listname) VALUES (userid, ','||friend_userid||',',1,','||friend_name||',');
            RETURN 2;
        EXCEPTION WHEN unique_violation THEN
        RETURN 0;
            -- do nothing, and loop to try the UPDATE again
        END;
    END LOOP;
END;
$$
LANGUAGE plpgsql;

--添加
select add_friend(1,1,'wangbin1');
select add_friend(1,2,'wangbin2');
select add_friend(2,1,'wangbin1');
select add_friend(2,2,'wangbin2');
select add_friend(3,1,'wangbin1');
select add_friend(3,2,'wangbin2');