'In' operator in mySQL
Employee: | id | name | department | managerId | +-----+-------+------------+-----------+ | 101 | John | A | null | | 102 | Dan | A | 101 | | 103 | James | A | 101 | | 104…
Html – How to match the student to his own teacher?
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…
UNLOGGED table and ROLLBACK in PostgreSQL
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…
In MySQL why := is executed inside of case statement even if the condition is False and how can I fix this?
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…
PostgreSQL window function for sum per interval
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),…
BigQuery extract one attribute across a JSON array of JSON objects
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…
Mysql – How to get each average of multiple items?
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…
How to correctly call a function in PostgreSQL
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:…
Postgresql – Identify groups of sequential records
I have very simple table: create table tmp( id int, source_id int, event_user varchar, event_date timestamp ); and here is the data: insert into tmp(id, source_id, event_user, event_date) values (1, 1, 'A', now()), (2, 1, 'A', now()+interval '1 day'), (3,…
Asp.net – Read a SQL-DOUBLE column as raw
I have data defined as double saved in a PSQL-Database (Actian) and I'm using DbDataReader to read the values. I know I can use GetDouble to read the value, but I would like read the raw value into a byte…