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Postgresql SELECT sample with FOR loop

I have a task where I need to create a 1000 sample row limit query for each attribute selected. So for example if I have: I would need to turn this in to: Problem is that I have a lot of these attributes and that I might be adding more attributes later. Is there a better way of writing this?

Sample from groups proportional to score

I have data with the following structure: CREATE TABLE if not EXISTS scores ( id int, class char, score float ); INSERT INTO scores VALUES (1, ‘A’, 0.5), (1, ‘B’, 0.2), (1, ‘C’, 0.1), (2, ‘A’, …

How to prevent unintended default values from MyBatis queries?

I have the following Java class: The class represents a database table called example. I can use the following SQL query to fetch Example instances from the table with MyBatis: Let’s say that I will add a new field to the table and the class: boolean third. However, if I don’t remember to add the …

Group by month and name SQL

I need some help with SQL. I have Table1 with columns Id, Date1 and Date2 Table2 with columns Table1Id and Table2Id Table3 with columns Id and Name Here is my try: I need to take Count(date2)/Count(date1) grouped by monthes and name. I have no idea how to do that, as there is no table with monthes. DB –…