aggregate-functions

I want to know how can i find all the values that are NULL in the MySQL database for example I'm trying to display all the users who don't have an average yet. Here is the MySQL code. SELECT COUNT(average) as num FROM users WHERE user_id = '$user_id' AND average IS_NULL SELECT COUNT(*) as num FROM users WHERE user_id = '$user_id' AND average IS NULL A more generic version (that doesn't depend on the where clause and hence limits your overall results): SELECT SUM(CASE WHEN average IS NULL THEN 1 ELSE 0 END) As null_num, SUM(CASE WHEN average IS NOT NULL THEN 1 ELSE 0 END) AS not_null_num FROM

I would like to aggregate two columns into one "array" when grouping. Assume a table like so: friends_map: ================================= user_id friend_id confirmed ================================= 1 2 true 1 3 false 2 1 true 2 3 true 1 4 false I would like to select from this table and group by user_id and get friend_id and confirmed as a concatenated value separated by a comma. Currently I have this: SELECT user_id, array_agg(friend_id) as friends, array_agg(confirmed) as confirmed FROM friend_map WHERE user_id = 1 GROUP BY user_id which gets me: ================================= user

I need to calculate percentages of various dimensions in a table. I'd like to simplify things by using window functions to calculate the denominator, however I am having an issue because the numerator has to be an aggregate as well. As a simple example, take the following table: create temp table test (d1 text, d2 text, v numeric); insert into test values ('a','x',5), ('a','y',5), ('a','y',10), ('b','x',20); If I just want to calculate the share of each individual row out of d1, then windowing functions work fine: select d1, d2, v/sum(v) over (partition by d1) from test; "b";"x";1.00 "a";"x";0

Currently working with a MLS data dump in which all their dates are formatted in MM/DD/YYYY , Trying to get the min/max age MIN( DateDiff( NOW(), idx_common.list_date ))) AS listage_min, MAX( DateDiff( NOW(), idx_common.list_date ))) AS listage_max Obviously this does not work because idx_common.list_date is in said format. Any ideas? Use str_to_date to convert idx_common.list_date . MIN( DateDiff( NOW(), str_to_date(idx_common.list_date,'%m/%d/%Y') ))) AS listage_min, MAX( DateDiff( NOW(), str_to_date(idx_common.list_date,'%m/%d/%Y') ))) AS listage_max http://dev.mysql.com/doc/refman/5.5/en

I have a table with two fields, TAG_ID and TAG_DESC my primary is tag_id. I'm looking for a query that will display each TAG_DESC and the amount of times it occurs next to it. Thanks, Ledhund SELECT TAG_DESC as 'Description', COUNT(TAG_DESC) as 'Occurances' FROM table_name GROUP BY TAG_DESC select TAG_DESC, count(*) from MyTable group by TAG_DESC 来源： https://stackoverflow.com/questions/3808062/counting-mysql-values

This question already has an answer here: Return multiple aggregate columns in LINQ 4 answers I'm trying to achieve the following in LINQ (EF6): SELECT count(A), sum(B), average(C) FROM TableA, LEFT JOIN TableB ON ... LEFT JOIN TableC ON ... WHERE (very complicated conditions) The C# code looks like following: IQueryable<Entity> = dbSet .Include(e => e.entityB) .Include(e => e.EntityC) .Where( <very complicated conditions> ); How can I apply multiple aggregate functions on different fields? Specifically, in a way, which won't cause the complicated conditions to be copied over and over in