I have two tables, one that looks like this: The other has the countries' populations: I would like to sum up the revenue by country (I know how to do this part, e.g Select Sum(Revenue), Country from COMPANIES GROUP BY…
example I have the following string values '[123] X' '[123] Y' '[123] Z' ... I want to bulk change them to 'X [123]' 'Y [123]' 'Z [123]' ... X, Y, Z are completely random not sequential [123] is constant I…
Employee: | id | name | department | managerId | +-----+-------+------------+-----------+ | 101 | John | A | null | | 102 | Dan | A | 101 | | 103 | James | A | 101 | | 104…
There are 3 classes, each with 10 students. Each class has their own homeroom teacher. When a student submits the form and chooses his homeroom teacher's identity, I have to make sure that he chooses his own teacher. Otherwise, error…
From the documentation, my understanding is that when a ROLLBACK command is issued in a transaction, PostgreSQL typically employs the Write-Ahead Logging (WAL) mechanism to undo the changes made within that transaction. However, because changes made to UNLOGGED tables bypass…
This problem I am trying to solve on HackerRank. In this problem, I have to group consecutive dates. Two dates are consecutive when the difference between two dates is 1 and in this problem statement, the start date and end…
The table is represented by following scripts: CREATE TABLE sales ( id SERIAL PRIMARY KEY, product_id INTEGER, sales_date DATE, quantity INTEGER, price NUMERIC ); INSERT INTO sales (product_id, sales_date, quantity, price) VALUES (1, '2023-01-01', 10, 10.00), (1, '2023-01-02', 12, 12.00),…
I want to modify the following query to extract the value attribute from the objects in the JSON array and output a table as follows: "value1", "value2" However my query currently outputs the whole JSON object for each entry in…
There is a table storing name, speed and timestamp of cars. Each car sends its speed at irregular time intervals, some send more often, some may have not sent their data for a couple of hours, simplified example (real table…
I have created a function that does not give any errors itself but when calling it I get an error. I know I technically don't need a function but for my scenario I need to be using one. The error:…