group-by

MySQL: group by and IF statement

By default, parent_id = 0. I want to select all records with parent_id = 0 and only the last ones with parent_id > 0. I tried this, but it didn't work: SELECT * FROM `articles` IF `parent_id` > 0 THEN GROUP BY `parent_id` HAVING COUNT(`parent_id`) >= 1 END; ORDER BY `time` DESC I mean, that if there are a few records with parent_id...

In ruby on rails, is it possible to do a sum query with group by using the find_each batching?

I'm loading data from my database and I'm doing a sum calculation with a group by. ElectricityReading.sum(:electricity_value, :group => "electricity_timestamp", :having => ["electricity_timestamp = '2010-02-14 23:30:00'"]) My data sets are extremely large, 100k upwards so I was wondering if its possible to use the find_each to batch ...

MySQL Group By and bracketing according to age.

Is that possible that MySQL can handle grouping of data according to age bracket? In my users table, age value is their actual age. I want to group them according to age bracket. For example: ages below 1 year old as age1, 1-4 yrs as age2, 5-9 yrs. old as age3 and so on. ...

Working by group by for grouping data into string format

I have a table that contains some data given below. It uses a tree like structure i.e. Department SubD1, SubD2 ..... PreSubD1, PreSubD1... PreSubD2, PreSubD2... pk_map_id preferences ImmediateParent Department_Id -------------------- ---------------...

how do I deconstruct COUNT()?

I have a view with some joins in it. I'm doing a select from that view with COUNT(*) as one of the columns of the select. I'm surprised by the number it's returning. Note that there is no GROUP BY nor aggregate column statement in the source view that the query is drawing from. How can I take it apart to see how it arrives at this numb...

MYSQL Select statment Order By with Group By

I have the following simple SQL statment SELECT id, name, value_name, value_id FROM table GROUP BY id ORDER BY value_id DESC when grouping I would like to get the value_name and value_id of the tuple where the value_id is the biggest. The way it is i am getting the smallest value. For example 1, name1, valuename, 3 (where i know ...

postgres - group by on multiple columns - master/detail type table

I have a table order(orderid, ordernumber, clientid, orderdesc etc.,) and a corresponding status for that order on an order_status table ( statusid, orderid, statusdesc, statusNote, statustimestamp) say I have a record in order as below orderid orderumber clientid orderdesc 1111 00980065 ABC blah..blah.....

How can I create a dynamic LINQ query in C# with possible multiple group by clauses?

I have been a programmer for some years now but I am a newcomer to LINQ and C# so forgive me if my question sounds particularly stupid. I hope someone may be able to point me in the right direction. My task is to come up with the ability to form a dynamic multiple group by linq query within a c# script using a generic list as a source. ...

How do I select and group by a portion of a string?

Given I have data like the following, how can I select and group by portions of a string? Version Users 1.1.1 1 1.1.23 3 1.1.45 1 2.1.24 3 2.1.12 1 2.1.45 3 3.1.10 1 3.1.23 3 What I want is to sum up the users using version 1.1.x and 2.2.x and 3.3.x etc, but I'm not sure how I can group on a partial string in a selec...

MySQL: Return grouped fields where the group is not empty, efficiently

In one statement I'm trying to group rows of one table by joining to another table. I want to only get grouped rows where their grouped result is not empty. Ex. Items and Categories SELECT Category.id FROM Item, Category WHERE Category.id = Item.categoryId GROUP BY Category.id HAVING COUNT(Item.id) > 0 The above query gives me the re...

Linq GroupBy - how to specify the grouping key at runtime?

is there a good way to do a Linq GroupBy where the grouping key is determined at runtime? e.g. I want the grouping key to be built from a user-selected list of fields - can you do this? I know I can do it easily if I convert everything to a table of strings, but I was wondering if there was an elegant or clever way to accomplish this oth...

NHIbernate Linq group by count

Hi I have the version 3.0.0.1001 nhibernate. My objects are basically modeiling a lineup at an event. So I have a StageSet object which represents one slot in the schedule for a stage. Each StageSet object has a Stage and an Act property. It also has many Users - people who have favorited the set. I'm trying to ascertain the most po...

SQL Server Distinct Question

I need to be able to select only the first row for each name that has the greatest value. I have a table with the following: id name value 0 JOHN 123 1 STEVE 125 2 JOHN 127 3 JOHN 126 So I am looking to return: id name value 1 STEVE 125 2 JOHN 127 Any idea on the MSSQL Syntax on how to perform this operation?...

LINQ Group By to project into a non-anonymous type?

Hi, I have the following LINQ example: var colorDistribution = from product in ctx.Products group product by product.Color into productColors select new { Color = productColors.Key, Count = productColors.Count() }; All this works and makes perfect sense. What I'm trying to achieve is...

cakePHP and GROUP BY

I am trying to solve a hopefully simple problem here is the query I am trying produce: SELECT `categories`.*, COUNT(`entities`.id) FROM `categories` LEFT JOIN `entities` ON (`categories`.`id` = `entities`.`category_id`) GROUP BY `categories`.`id` I am really struggling to do this is in cakePHP 1.2 How would/should I go about doing t...

SQL Max Group By Query Help

Hi All, I have a quick question. How do I select the two values I need in one query? Currently I'm doing this, which works fine, but it's obviously running two queries when one should do the trick. I tried MAX(columnA) and GROUP BY ColumnB, but that returns multiple row. I only want one row returned. DECLARE @biID bigint , @dtThresho...

Need some sort of "conditional grouping" in MySQL.

I have Article table: id | type | date ----------------------- 1 | A | 2010-01-01 2 | A | 2010-01-01 3 | B | 2010-01-01 Field type can be A, B or C. I need to run a report that would return how many articles of each type there is per every day, like this: date | count(type="A") | count(type="B") | count(type="C") -...

Counting multiple rows in MySQL in one query

I currently have a table which stores a load of statistics such as views, downloads, purchases etc. for a multiple number of items. To get a single operation count on each item I can use the following query: SELECT *, COUNT(*) FROM stats WHERE operation = 'view' GROUP BY item_id This gives me all the items and a count of their views. ...

SQL DISTINCT Value Question

How can I filter my results in a Query? example I have 5 Records John,Smith,apple Jane,Doe,apple Fred,James,apple Bill,evans,orange Willma,Jones,grape Now I want a query that would bring me back 3 records with the DISTINCT FRUIT, BUT... and here is the tricky part, I still want the columns for First Name , Last Name. PS ...

Linq 2 SQL Grouping Question

var groups = from p in dc.Pool join pm in dc.PoolMembers on p.ID equals pm.PoolID group p by p.Group into grp select new { grp.ID }; This isn't working. Basically I want to do the grouping, and then select certain columns, but when I do select new { grp. } I get no intellisense, so I'm obviously ...