I have a codescore table which will soon cross 500,000 rows of dummy data. The table is used to hold the points scored by players in a game. Following are the columns present in the table.
questionid bigint,
playerid varchar(20),
playerscore float,
questionlevel enum('EASY', 'MODERATE', 'HARD'),
questionstatus enum('PENDING','SOLVED'),
lastmodified datetime,
created datetime
Primary key (questionid, playerid)
Sample data:
+------------+----------+-------------+----------------+
| questionid | playerid | playerscore | questionstatus |
+------------+----------+-------------+----------------+
| 1 | 1 | 5 | PENDING |
+------------+----------+-------------+----------------+
| 1 | 2 | 10 | SOLVED |
+------------+----------+-------------+----------------+
| 3 | 1 | 10 | SOLVED |
+------------+----------+-------------+----------------+
| 2 | 3 | 10 | SOLVED |
+------------+----------+-------------+----------------+
Each questionid has some points associated with it and when a player solves the problem correctly he is awarded the points and an entry in made in the codescore table and the questionstatus for that entry is set to SOLVED. If the player has partially solved a problem then some part of the total points is awarded to the player and an entry is made in the table with questionstatus set to PENDING.
A player can solve a given problem any number of times as long as the status is PENDING, to improve his score. Once the status is changed to SOLVED then no more score update is done. Though the player is still allowed to solve the problem for practicing.
Now the main part of the problem:
Find top 10 players (order by score in decreasing order) for each questionlevel (EASY, MODERATE, HARD)
Using the following query to find top 10 players for the HARD level:
SELECT playerid, SUM(playerscore) AS score FROM codescore
WHERE questionlevel = 'HARD'
GROUP BY playerid
ORDER BY score DESC
LIMIT 10;
Is the above query going to work well if the records in the table crosses 500K or 1 Million rows in production environment?
Is there any better solution for this type of problem or a better query that can be used to accomplish this task?
[Backend: using MySQL and CodeIgniter]
Related
Looking around the site, most questions regarding to Ranks in a highscore table assumes that you will be looking at the entire or the top of the table.
In a lot of examples on this site, the rank is found by ordering the items by score and then counting the rows from the top of the set, or counting the items as they are retrived. Like this
score name rank
1000 test345 1
999 test980 2
950 test234 3
833 test291 4
760 test573 5
731 test981 6
In my situation, I need to look at only a portion of the scores, which may not be at the top of the table, for instance, maybe halfway though the leaderboard:
scores name rank
500 test451 43
433 test768 44
425 test120 45
where the user is only shown the scores around his. The part of the leader board the user is looking at above, isn't at the top of the leader board, so I can't count the rows in the returned scores to determine their rank.
How can I determine the rank of user in a leader board at and arbitrary position efficiently, amusing there a lot of entries.
Also this is my first foray into sql and php. I might not be using the correct terminology.
I'm not really sure what you are trying to do. You can limit you result using a LIMIT clause like this:
SELECT * FROM <table> LIMIT 0, 3
Which will only return the first 3 records.
To order the result based on the rank field you would use an ORDER BY clause:
SELECT * FROM <table> ORDER BY rank DESC LIMIT 0, 3
The above query will return 3 records order by rank in descending order.
If you like to calculate the rank based on the scores column this would work:
SELECT scores,
name,
FIND_IN_SET(scores, (SELECT GROUP_CONCAT(scores ORDER BY scores DESC)
FROM <table>)) as rank
FROM <table> ORDER BY rank DESC LIMIT 0, 3;
Running the above query against a table with only two columns scores and name:
+--------+---------+
| scores | name |
+--------+---------+
| 500 | test451 |
| 433 | test768 |
| 425 | test120 |
| 300 | test001 |
| 250 | test002 |
| 200 | test003 |
+--------+---------+
Would yield the following result:
+--------+---------+------+
| scores | name | rank |
+--------+---------+------+
| 500 | test451 | 1 |
| 433 | test768 | 2 |
| 425 | test120 | 3 |
+--------+---------+------+
The GROUP_CONCAT() maximum length is depending on the group_concat_max_len system variable, so for a large table this needs to be changed and I'm not sure this would be the best approach.
Notice that you could/should add indexes to your table to speed things up:
ALTER <table> ADD INDEX `idx_scores` (`scores`);
I am attempting at making a site that has a polling section in it. The users need to be able to take previous polls if they have not voted in them yet. So for each poll they take, it adds a note into the cell.
The table looks something like this:
userid | poll1 | poll2 | poll3 | poll4 /
---------+--------+--------+-------+--------/
001 | Y | Y | | /
---------+--------+--------+-------+--------/
002 | Y | | Y | /
--------------------------------------------/
So now, the code would have to select poll 3 and 4 for user 001, and present that to the user on the page. I have been trying a couple different approaches to this but can't seem to find the right code.
I have looked for something for help online and haven't found anything that addresses this issue.
Users
id | name
---+-------
1 | tyrion
2 | cersei
Polls
id | name
---+-------
1 | first poll
2 | second poll
UserPolls
user_id | poll_id
--------+-------
1 | 1
1 | 2
2 | 2
In the above table structure, you have the two main object tables, and one relational table, called UserPolls. This will scale pretty well, for any number of polls you want.
Then, if you want to know which polls were taken by a given user, you can do:
SELECT poll_id FROM UserPolls WHERE user_id = 1
Or if you want the opposite. Polls not taken by a given user:
SELECT id FROM Polls WHERE Polls.id NOT IN (SELECT poll_id FROM UserPolls WHERE user_id = 1)
Note: this is not tested code, but you get the general idea on how to go about designing and normalizing your tables.
I am trying to figure out how to rank based on 2 different column numbers in laravel but raw mysql will do. I have a list of videos, these videos are inside of competitions and are given votes if someone likes the video. Each video will have a vote number and a competition number. I am trying to rank based on votes within competition. So for example below I have competition 8, I need the rank of all the videos in that competition based on votes. I then need the same for competition 5 etc.
|rank|votes|competition|
------------------
| 1 | 100 | 8 |
------------------
| 2 | 50 | 8 |
------------------
| 3 | 30 | 5 |
------------------
| 1 | 900 | 5 |
------------------
| 2 | 35 | 5 |
------------------
I have tried various group and selectby methods but nothing seems to work, any ideas?
In Mysql you can use user-defined variables to calculate rank,case statement checks if competition is same as the previous row then increment rank by one if different then assign 1 an order by is needed to have correct rank for the video
SELECT t.*,
#current_rank:= CASE WHEN #current_rank = competition
THEN #video_rank:=#video_rank +1
ELSE #video_rank:=1 END video_rank,
#current_rank:=competition
FROM t ,
(SELECT #video_rank:=0,#current_rank:=0) r
ORDER BY competition desc, votes desc
See Demo
If you are confused with the last extra column you can use a subselect
See Demo
You can use windowing functions:
select
competition, votes, rank() over (partition by competition order by votes desc) as rank
from
table1
I wanted to create a system to track the progress of a player in a game. Each player can be a member of multiple groups, which all have other requirements. In order to track his progress, the stats of the player will be saved once he joins a group. Every time he reloads his stats, the current ones should be saved inside the database.
All stats of the player are stored in a json-format, which will then be parsed either by PHP or JS. An entry with compare = 0 is set once the player joins a group. An entry with compare = 1 should be created the first time a player clicks on Update Stats and from then on it should only be updated, not newly created.
Now my question is: How to achieve that? When reading through the syntax of INSERT INTO I got the following:
INSERT INTO `groups` (`grp`, `id`, `json`, `compare`) VALUES
($grp, $id, $json, 1) ON DUPLICATE KEY SET `json` = $json
However, since there is no key set, and I don't know if I can set up two/three keys (as there can be multiple groups per user, as well as the compare = 0 entry in the same group), I don't think I can do it this way.
+------+----+---------+---------+
| grp | id | json | compare |
+------+----+---------+---------+
| 1 | 1 | stats | 0 |
| 1 | 1 | stats | 1 |
| 1 | 2 | stats | 0 |
| 1 | 2 | stats | 1 |
| 2 | 2 | stats | 0 |
| 2 | 3 | stats | 0 |
| 2 | 3 | stats | 1 |
| 2 | 4 | stats | 0 |
| 2 | 5 | stats | 0 |
+------+----+---------+---------+
grp is the group of the player. There is no real limit set to the
number of groups a player can be in.
id is the ID of the player.
json contains the stats of the player in a json
format (number of points, etc).
compare is a boolean. 0 stands for entry stats (the number of points a player
already had when he registered) and 1 stands for the current stats - Which will
be compared to the entry stats, in order to get the difference (= the points a
player made since joining the group).
I hope my explanation was understandable and someone can help me out.
You can use insert raplace:
REPLACE INTO groups (`grp`, `id`, `json`, `compare`) VALUES (...);
But you must have primary key in table. Replace into automaticly finds out primary key and if record exists, it update row, but if doesn't, it add new row.
You can create a unique key with multiple columns. This will trigger the 'on duplicate' clause.
ALTER TABLE groups
ADD UNIQUE (grp, id, compare)
I'm trying to output a "scoreboard"/"standings" list of hockey players. I currently have a MySQL table like this:
statsID | matchID | playerID | goals | assists
120 | 2 | 3 | 4 | 1
121 | 2 | 4 | 2 | 2
122 | 3 | 3 | 0 | 3
So for each match the players gets added along with goals and assists. This means that there's multiple entries (several matches) for each player.
So basically, is there a good way to fetch the player data, summarize goals and assists (+ overall points) and output it in a list?
Right now, I have a basic query just outputting each row (as far as my current knowledge reaches). So how can I just output one entry of each player with his stats summarized?
Here's one approach:
SELECT t.playerID
, SUM(t.goals) AS total_goals
, SUM(t.assists) AS total_assists
FROM sometable t
GROUP BY t.playerID
ORDER BY t.playerID
Not clear what calculation you use for "overall points", if you are just adding goals and assists, then you can use this in the SELECT list:
, SUM(t.goals)+SUM(t.assists) AS overall_points
You need to use a group by clause.
SELECT playerID, SUM(goals + assist) overall points
FROM table_name
GROUP BY playerID