There is a table messages that contains data as shown below: Id Name Other_Columns ------------------------- 1 A A_data_1 2 A A_data_2 3 A A_data_3 4 B B_data_1 5 B B_data_2 6 C C_data_1 If I ru...

I read many threads about getting only the first row of a left join, but, for some reason, this does not work for me. Here is my structure (simplified of course) Feeds id | title | content -----...

I have an employee table with a name and a salary. I want to print these 2 columns with only 2 records in them, the name of my highest and lowest payed employee. It should look something like thi...

I have this table for documents (simplified version here): id rev content 1 1 ... 2 1 ... 1 2 ... 1 3 ... How do I select one row per id and only the greatest rev? With t...

a.2<-sample(1:10,100,replace=T) b.2<-sample(1:100,100,replace=T) a.3<-data.frame(a.2,b.2) r<-sapply(split(a.3,a.2),function(x) which.max(x$b.2)) a.3[r,] returns the list index, not ...

I have the following table: CREATE TABLE orders ( id INT PRIMARY KEY IDENTITY, oDate DATE NOT NULL, oName VARCHAR(32) NOT NULL, oItem INT, oQty INT -- ... ); INSERT INTO orders VALUES (1, ...

I need to find a running maximum of a variable by group using R. The variable is sorted by time within group using df[order(df$group, df$time),]. My variable has some NA's but I can deal with it b...

select * from records where id in ( select max(id) from records group by option_id ) This query works fine even on millions of rows. However as you can see from the result of explain statement:...

Although this question looks simple, it is kind of tricky. Consider the following table: CREATE TABLE A ( id INT, value FLOAT, "date" DATETIME, group VARCHAR(50) ); I would like to ...

Let's say I have a payments table like so: CREATE TABLE Payments ( PaymentID INT, CustomerID INT, Value INT, PaidOn DATE ); INSERT INTO Payments VALUES (1, 1, 5, '2000-01-01'), (2, 1, 10, '20...