greatest-n-per-group

I'm trying to create a Flask app that shows the latest score from individual players. So a player can have multiple scores, but on the leaderboard I only want to show her most recent score. My models.py: class Player(db.Model): __tablename__ = 'player' id = db.Column(db.Integer, primary_key=True) firstname = db.Column(db.String, nullable=False) score = db.relationship('Score', backref='player', lazy='dynamic') def __init__(self, firstname): self.firstname = firstname def __repr__(self): return '<id {}>'.format(self.id) class Score(db.Model): __tablename__ = 'score' id = db.Column(db.Integer,

Now that I got the Select all forums and get latest post too.. how? question answered, I am trying to write a query to select all threads in one particular forum and order them by the date of the latest post (column "updated_at"). This is my structure again: forums forum_threads forum_posts ---------- ------------- ----------- id id id parent_forum (NULLABLE) forum_id content name user_id thread_id description title user_id icon views updated_at created_at created_at updated_at last_post_id (NULLABLE) I tried writing this query, and it works.. but not as expected: It doesn't order the threads

I have the following table structure: Item ID | Name -------- 1 | Apple 2 | Pear 3 | Banana 4 | Plum 5 | Tomato Event ItemStart | ItemEnd | EventType | EventDate -------------------------------------------- 1 | 2 | Planted | 2014-01-01 1 | 3 | Picked | 2014-01-02 3 | 5 | Eaten | 2014-01-05 The two tables are linked only by the primary key of Item and the range of ItemStart and ItemEnd (inclusive) in Event. Events always refer to contiguous sequences of Items, but not all the Events for a given Item will have the same range. Events never occur on the same date for a given Item. The query I'd

Following my recent question Select information from last item and join to the total amount , I am having some memory problems while generation tables I have two tables sales1 and sales2 like this: id | dates | customer | sale With this table definition: CREATE TABLE sales ( id int auto_increment primary key, dates date, customer int, sale int ); sales1 and sales2 have the same definition, but sales2 has sale=-1 in every field. A customer can be in none, one or both tables. Both tables have around 300.000 records and much more fields than indicated here (around 50 fields). They are InnoDB. I

This is my table structure: File | Version | Function 1 | 1 | 1 1 | 2 | 1 1 | 3 | 1 1 | 2 | 2 2 | 1 | 4 3 | 2 | 5 I need it to return these rows only 1 | 3 | 1 2 | 1 | 4 3 | 2 | 5 Meaning I only want the functions that have the most recent version for each file. I do not want the result below, i.e unique function ids that are not the most recent version 1 | 3 | 1 1 | 2 | 2 ... I've looked at How can I SELECT rows with MAX(Column value), DISTINCT by another column in SQL? , but that returns the most recent unique function ids. The query needs to be sqlite3 compatible. An efficient way to do