I have a very simple SQL query: SELECT COUNT(DISTINCT x) FROM table; My table has about 1.5 million rows. This query is running pretty slowly; it takes about 7.5s, compared to SELECT COUNT(x) FROM table; which takes about 435ms. Is there any way to change my query to improve performance? I’ve tried grouping and doing … Read more
In C#, say I have a class called Note with three string member variables. public class Note { public string Title; public string Author; public string Text; } And I have a list of type Note: List<Note> Notes = new List<Note>(); What would be the cleanest way to get a list of all distinct values … Read more
I am trying to find a MySQL query that will find DISTINCT values in a particular field, count the number of occurrences of that value and then order the results by the count. example db id name —– —— 1 Mark 2 Mike 3 Paul 4 Mike 5 Mike 6 John 7 Mark expected result … Read more
I have a ksh script that returns a long list of values, newline separated, and I want to see only the unique/distinct values. It is possible to do this? For example, say my output is file suffixes in a directory: tar gz java gz java tar class class I want to see a list like: … Read more
If I have a table CREATE TABLE users ( id int(10) unsigned NOT NULL auto_increment, name varchar(255) NOT NULL, profession varchar(255) NOT NULL, employer varchar(255) NOT NULL, PRIMARY KEY (id) ) and I want to get all unique values of profession field, what would be faster (or recommended): SELECT DISTINCT u.profession FROM users u or … Read more
I am using Pandas as a database substitute as I have multiple databases (Oracle, SQL Server, etc.), and I am unable to make a sequence of commands to a SQL equivalent. I have a table loaded in a DataFrame with some columns: YEARMONTH, CLIENTCODE, SIZE, etc., etc. In SQL, to count the amount of different clients … Read more
I can select all the distinct values in a column in the following ways: SELECT DISTINCT column_name FROM table_name; SELECT column_name FROM table_name GROUP BY column_name; But how do I get the row count from that query? Is a subquery required? 12 Answers 12
I learned something simple about SQL the other day: SELECT c FROM myTbl GROUP BY C Has the same result as: SELECT DISTINCT C FROM myTbl What I am curious of, is there anything different in the way an SQL engine processes the command, or are they truly the same thing? I personally prefer the … Read more
SELECT DISTINCT field1, field2, field3, …… FROM table I am trying to accomplish the following sql statement but I want it to return all columns is this possible? Something like: SELECT DISTINCT field1, * from table 18 Answers 18
I need to retrieve all rows from a table where 2 columns combined are all different. So I want all the sales that do not have any other sales that happened on the same day for the same price. The sales that are unique based on day and price will get updated to an active … Read more
