sql-order-by

I have a table of products: CREATE TABLE products (`id` INT); And a table of images for those products: CREATE TABLE images (`id` INT, `product_id` INT, `default` TINYINT(1)); I need to select all the products, and join the images table so that images with ( default = 1) will be preferred, and if a product has no images with ( default = 1), an image with ( default = 0) will be shown in its place. Here's an image showing what I'm looking for: Right now I have this query: SELECT p.id, i.id FROM products AS p LEFT JOIN ( SELECT product_id, url FROM images ORDER BY default ) AS i ON p.id = i

I would like to sort a collection based on a subcollection property. //the subcollection public class Salary { public int SalaryId {get;set;} public int SalaryYear {get;set;} public double SalaryValue {get;set;} //this is the field we want to sort the parent collection "Person" } //the main collection public class Person { public int PersonId {get;set;} public string PersonName {get;set;} public List<Salary> Salaries {get;set;} } Below just for testing purpose, I'm preparing my collection of person with Salaries inner collections each one: List<Person> people = new List<Person>(); //add two

I am working on category management. Where i have parentId with each row. Categories can be n-level. I can recursively call php function which will return category tree array. Now Issue is: In admin panel i want category listing page as shown below. i.e. which category is under which. Home Products (Edit) (Delete) Products > Product 1 (Edit) (Delete) Products > Product 2 (Edit) (Delete) Products > Product 2 > Product 2 1 (Edit) (Delete) Products > Product 2 > Product 2 2 (Edit) (Delete) Contact Us (Edit) (Delete) I want mysql query result in same order as shown above. I am not sure how can i

Probably what I'm asking is quite simple but I don't seem to be getting this one out. I have a list of elements containing a Date field and a Time field. The Date field is a regular DateTime and the Time field is a string. Time is formatted like HH:mm and ranges in 24h. Ordering my list by Date is simple by doing List.OrderBy(e => e.Date), but I don't seem to be able to later order it by Time so that the order of the records is according the date and the time. I tried this out but it's probably a big mistake! List = List.OrderBy(e => e.EstimatedDate).OrderBy(e => new TimeSpan(int.Parse(e

I'm using annotate to add a property to an object which I can then use for order_by. However, I want to annotate on a field of a relation on a relation. I know I should be able to get to the field somehow using double-underscore notation, but I just can't seem to wrap my head around it. Here are the models: class Group(Taggable, Uploadable): name = models.CharField(max_length=250, db_index=True) description = models.TextField(max_length=5000, null=True, blank=True, db_index=True) private = models.BooleanField(default=False) members = models.ManyToManyField(User, null=True, related_name=

I have a search query which yields a resultset based on input parameters and the result can be sorted (ASC/DESC) based on different parameters: price, duration etc (with pagination in place and limit of 10 records) I now have a requirement wherein, if I have an id passed in, I'd like the corresponding record to be made to sticky at the top in the given resultset. Lets say we have a package table like this: Package - id - name - mPrice - vPrice - duration // Searching pkg based on Price (in DESC order) where name = Thailand sqlQuery = "SELECT p.id, p.name, p.mPrice, p.vPrice FROM package p

When retrieving entries in a database, is there a difference between storing values as a float or decimal vs. an int when using ORDERBY in a SELECT statement? It depends. You didn't specify the RDBMS so I can only speak to SQL Server specifically but data types have different storage costs associated with them. Ints range from 1 to 8 bytes, Decimals are 5-17 and floats are 4 to 8 bytes. The RDBMS will need to read data pages off disk to find your data (worst case) and they can only fit so many rows on an 8k page of data. So, if you have 17 byte decimals, you're going to get 1/17th the amount

for example i have this table: itemgroup | description | price A, a, 10 A, b, 12 A, c, 14 B, g, 11 B, h, 16 now i want to select the rows with the highest price in one group like this: A, c, 14 B, h, 16 The SQL query (is fully functional) wich gets me near this is: SELECT itemgroup, MAX( price ) FROM table GROUP BY itemgroup A, 14 B, 16 By trying this I get an "not a GROUP BY expression"-error: SELECT itemgroup, description, MAX( price ) FROM table GROUP BY itemgroup I need something like this pseudo query: SELECT itemgroup, IGNORE( description), MAX( price ) FROM table GROUP BY itemgroup I

In our DB access layer we have some dynamic query creation. For instance, we have the following method for building a part of an ORDER BY clause: protected string BuildSortString(string sortColumn, string sortDirection, string defaultColumn) { if (String.IsNullOrEmpty(sortColumn)) { return defaultColumn; } return String.Format("{0} {1}", sortColumn, sortDirection); } The problem is, sortColumn and sortDirection both come from outside as strings, so of course something should be done to prevent possible injection attacks. Does anybody have any idea how this can be done? If you have to deal in