Selecting first records of a type in a given period

Posted by Emanuil Rusev on Stack Overflow See other posts from Stack Overflow or by Emanuil Rusev
Published on 2012-09-03T11:18:56Z Indexed on 2012/09/03 15:38 UTC
Read the original article Hit count: 170

Filed under:

mysql

|

select

I have a database table that stores user comments:

comments(id, user_id, created_at)

I want to get from it the number of users that have commented for the first time in the past week.

Here's what I have so far:

SELECT COUNT(DISTINCT `user_id`) 
FROM `comments` 
WHERE `created_at` BETWEEN DATE_SUB(NOW(), INTERVAL 7 DAY) AND NOW()

This would give the number of users that have commented, but it would not take into consideration whether these comments are first for these users.

© Stack Overflow or respective owner

Related posts about mysql

How to remove MySQL completely with config and library files on ubuntu 12.04 gnome 3.0

as seen on Ask Ubuntu - Search for 'Ask Ubuntu'
I tried everything till now: sudo apt-get remove mysql-server mysql-client mysql-common sudo apt-get purge mysql-server mysql-client mysql-common sudo apt-get autoremove and even more commands... But whenever I am trying to locate mysql. I get a no. of files related to mysql command: shell>>… >>> More
mysql: Cannot load from mysql.proc. The table is probably corrupted

as seen on Server Fault - Search for 'Server Fault'
Mysql was started: /usr/bin/mysqld_safe --datadir=/srv/mysql/myDB --log-error=/srv/mysql/logs/mysqld-myDB.log --pid-file=/srv/mysql/pids/mysqld-myDB.pid --user=mysql --socket=/srv/mysql/sockets/mysql-myDB.sock --port=3700 but when I'm trying to do something: ERROR 1548 (HY000) at line 1: Cannot… >>> More
Why is there a /etc/init.d/mysql file on this Slackware machine? How could it have gotten there?

as seen on Server Fault - Search for 'Server Fault'
A client of my IT-consulting service owns a web-development shop. He's been having problems with a Slackware 12.0 server running MySQL 5.0.67. The machine was set up by the client's sysadmin, who left on bad terms. My client no longer employs a sysadmin. As far as I can tell, the only copy of MySQL… >>> More
mysql: Bind on unix socket: Permission denied

as seen on Server Fault - Search for 'Server Fault'
Can't start mysql with: sudo /usr/bin/mysqld_safe --datadir=/srv/mysql/myDB --log-error=/srv/mysql/logs/mysqld-myDB.log --pid-file=/srv/mysql/pids/mysqld-myDB.pid --user=mysql --socket=/srv/mysql/sockets/mysql-myDB.sock --port=3700 120222 13:40:48 mysqld_safe Starting mysqld daemon with databases… >>> More
MySQL – Learning MySQL Online in 6 Hours – MySQL Fundamentals in 320 Minutes

as seen on SQL Authority - Search for 'SQL Authority'
MySQL is one of the most popular database language and I have been recently working with it a lot. Data have no barrier and every database have their own place. I have been working with MySQL for quite a while and just like SQL Server, I often find lots of people asking me if I have a tutorial which… >>> More

Related posts about select

HTML muliple select should look like HTML select

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi I am trying to use a HTML select box with 'multiple' select options and size to 1 as below ` <SELECT NAME="toppings" MULTIPLE SIZE=5> <OPTION VALUE="mushrooms">mushrooms <OPTION VALUE="greenpeppers">green peppers </SELECT> When the size is set to 1 small scrollbar appears… >>> More
MySQL Query Select using sub-select takes too long

as seen on Stack Overflow - Search for 'Stack Overflow'
I noticed something strange while executing a select from 2 tables: SELECT * FROM table_1 WHERE id IN ( SELECT id_element FROM table_2 WHERE column_2=3103); This query took approximatively 242 seconds. But when I executed the subquery SELECT id_element FROM table_2 WHERE column_2=3103 it… >>> More
SQL SERVER- IF EXISTS(Select null from table) vs IF EXISTS(Select 1 from table)

as seen on SQL Authority - Search for 'SQL Authority'
Few days ago I wrote article about SQL SERVER – Stored Procedure Optimization Tips – Best Practices. I received lots of comments on particular blog article. In fact, almost all the comments are very interesting. If you have not read all the comments, I strongly suggest to read them. Click here to… >>> More
Nesting Linq-to-Objects query within Linq-to-Entities query –what is happening under the covers?

as seen on Programmers - Search for 'Programmers'
var numbers = new int[] { 1, 2, 3, 4, 5 }; var contacts = from c in context.Contacts where c.ContactID == numbers.Max() | c.ContactID == numbers.FirstOrDefault() select c; foreach (var item in contacts) Console.WriteLine(item.ContactID); Linq-to-Entities… >>> More
Play Framework: Error getting sequence nextval using H2 in-memory database

as seen on Stack Overflow - Search for 'Stack Overflow'
As the title suggests, I get an error running Play 2.0.1 Tests using a FakeApplication w/ H2 in memory. I set up a basic unit test: public class ModelTest { @Test public void checkThatIndustriesExist() { running(fakeApplication(inMemoryDatabase()), new Runnable() { public… >>> More