Update and log only changed rows with SQL in SQLite - sql

Question

I am writing an application/script in R that updates a SQLite database.
My apologies - I am not experienced with this.
My table consists of 4 fields Id,Name,LVL,Notes:
CREATE TABLE members (
Id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT,
Name TEXT NOT NULL,
LVL INTEGER NOT NULL,
Notes TEXT
);
INSERT INTO members (Name,LVL,Notes)
VALUES ('Jean',12,'First stage'),
('Jacques',1,'Second stage'),
('Amelie',1,'Second stage'),
('Louis',13,'Some other note altogether')
;
I want to check it against another table tmp
CREATE TABLE tmp (
Name TEXT NOT NULL,
LVL INTEGER NOT NULL,
Notes TEXT
);
INSERT INTO tmp (Name,LVL,Notes)
VALUES ('Jean',13,'First stage'),
('Jacques',1,'Second stage'),
('Amelie',1,'Third stage'),
('Louis',14,'Fourth stage')
;
and if there are changes in LVL and/or Notes fields (as LVL for Jean and Louis and Notes for Amelie and Louis) I want to update the members table with new values after I record the previous values (as whole rows) with a timestamp in member_changes table.
What would be the minimal set of queries to achieve this?
And what is the better design of the member_changes table? Would it be the same as members but with added rowID as primary key and timestamp fields? And naturally memberID would allow duplicates.
Many thanks,
Rob
SYNOPSIS of expanded answer
Thanks to #forpas kind answer I put this small system together with 2 additional triggers. New information comes in via tmp table. Member names are presumed to be unique; possibly primary key on members.Id was not needed. Nevertheless:
-- CREATE members table for current guild members
-- Id is prim key and Name has unique index
CREATE TABLE members (
Id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT,
Name TEXT NOT NULL UNIQUE,
LVL INTEGER NOT NULL,
Notes TEXT
);
-- SAMPLE DATA
INSERT INTO members (Name,LVL,Notes) VALUES
('Jean',12,'First stage'),
('Jacques',1,'Second stage'),
('Amelie',1,'Second stage'),
('Louis',13,'Some other note altogether');
-- LOG table to see membership changes over time
CREATE TABLE members_changes (
timestamp TEXT DEFAULT CURRENT_TIMESTAMP,
Id INTEGER REFERENCES members(Id),
Name TEXT NOT NULL,
LVL INTEGER NOT NULL,
Notes TEXT
);
-- TABLE through which the updates will come in via rvest
-- presumed cannot contain duplicate names
CREATE TABLE tmp (
Name TEXT NOT NULL UNIQUE,
LVL INTEGER NOT NULL,
Notes TEXT
);
-- TRIGGERS (3)
-- (1) UPDATES MEMBERS if insertion in tmp shows changes
-- also LOGS this change in members_changes
CREATE TRIGGER IF NOT EXISTS tr_insert_tmp AFTER INSERT ON tmp
BEGIN
INSERT INTO members_changes(Id,Name,LVL,Notes)
SELECT Id,Name,LVL,Notes
FROM members
WHERE Name = NEW.NAME AND (LVL IS NOT NEW.LVL OR Notes IS NOT NEW.Notes);
UPDATE members
SET LVL = NEW.LVL, Notes = NEW.Notes
WHERE Name = NEW.Name AND (LVL IS NOT NEW.LVL OR Notes IS NOT NEW.Notes);
END;
-- (2) LOGS DELETIONS from members
CREATE TRIGGER IF NOT EXISTS tr_delete_members BEFORE DELETE ON members
BEGIN
INSERT INTO members_changes(Id,Name,LVL,Notes)
SELECT Id,Name,LVL,Notes || " :Deleted"
FROM members
WHERE Name = OLD.Name;
END;
-- (3) LOGS INSERTS into members (new members)
CREATE TRIGGER IF NOT EXISTS tr_insert_members AFTER INSERT ON members
BEGIN
INSERT INTO members_changes(Id,Name,LVL,Notes)
SELECT Id,Name,LVL,Notes || " :Inserted"
FROM members
WHERE Name = NEW.Name;
END;
-- this shows all defined triggers
select * from sqlite_master where type = 'trigger';
-- QUERIES to be run from the script after tmp is updated (b,c,d)
-- ADD NEW MEMBERS
-- it should mostly fail (changes are slow and few)
-- this is logged via tr_insert_members
INSERT OR IGNORE INTO members(Name,LVL,Notes) SELECT Name, LVL, Notes FROM tmp;
-- DELETE OLD MEMBERS
-- logged via tr_delete_members
DELETE FROM members WHERE Name NOT IN (SELECT Name FROM tmp);
-- EMPTY tmp at the end of the script run
DELETE FROM tmp;
When application runs the only queries that need to be called are:
a) the one which populates tmp (from dataframe gathered by rvest)
b) query to add new members from tmp
c) query to delete members not in tmp
d) query to empty tmp
This is thanks to database setup kindly suggested by #forpas. I had never used triggers and finally made some sense of them. Very helpful for logging changes.

Answer 1

A proper design for members_changes is this:
CREATE TABLE members_changes (
timestamp TEXT DEFAULT CURRENT_TIMESTAMP,
Id INTEGER REFERENCES members(Id),
Name TEXT NOT NULL,
LVL INTEGER NOT NULL,
Notes TEXT
);
The column timestamp's default value is the current timestamp.
You need an AFTER INSERT trigger for the table tmp, so that for every inserted row in tmp, the respective row from members will be inserted in members_changes (if any value of LVL or Notes is different) and after that the new row from tmp will update the row of members:
CREATE TRIGGER IF NOT EXISTS tr_insert_tmp AFTER INSERT ON tmp
BEGIN
INSERT INTO members_changes(Id,Name,LVL,Notes)
SELECT Id,Name,LVL,Notes
FROM members
WHERE Name = NEW.NAME AND (LVL IS NOT NEW.LVL OR Notes IS NOT NEW.Notes);
UPDATE members
SET LVL = NEW.LVL, Notes = NEW.Notes
WHERE Name = NEW.Name AND (LVL IS NOT NEW.LVL OR Notes IS NOT NEW.Notes);
END;
See the demo.