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Tag: sql

Bi-temporal SQL table querying

I’m trying to model a SQL table to store salary changes for employees. One approach is using a bi-temporal table as follows: Here an employee was hired on 10/1/2015 with salary of 100,000. Then on 2/15/2016 he had a performance review and his boss said, “we’re bumping your salary to 110,000 effective start of current year (1/1/2016). To store this

2 SELECT with INTERSECT or 2 condition with WHERE

I have a task that “Get the makers producing both PCs having a speed of 750 MHz or higher and laptops with a speed of 750 MHz or higher. Result set: maker” from https://www.sql-ex.ru For this task I wrote this query which is return nothing (empty screen) But the right query is I wonder what is the differences between these

Modify a query recordset to complete information (MS Access)

im working in a project in Microsoft access to query the date, hour and a quantity of products by line of production. However, I need to display all of the 24 hours of production in a column but cannot do it since I don’t have records for the missing hours. I’m using Totals to sum the quantity of products produced.

IIF or case when in window function

I have some timestamps in a table and I want to create a dummy variable (0 or 1) that tests if the row above is equal to the current row, after the timestamps are sorted. I need to do this in different partitions. Is there a window function that can do this in SQL Server? So I know my partition

MySQL – summing up products from several orders

I want to sum up the number of items purchased from several orders. I have this query, however it shows me each order on a separate row. I want have it all added up in one row. This is woocommerce database. Example output: and this is how it should be: Answer You want the aggregation string over all those items,

Query that merges latest reference in multiple tables into shared rows

I have the following schema which is pretty simple and straight forward: I want to write an optimized query that returns me a list of all phones with their latest message and latest picture taken. In this case with the latest “CreatedAt” for both fields: Example expected data-set: Right now I’m not sure how to write such a query so

MySql improve GROUP BY ORDER BY query with index

I have a table like this: the goal is to query how many products have been sold per day, so the query is: The output is: Ok. Now let us suppose we have a scenario with several records and this query has to be run several times per day, we need to care about performance now in order to retrive

StartDate invalid identifier

I have two SELECT statment which I connect using UNION and I get error Since I create first one SELECT statment and run and I get result, and second also, so I run separatly and it works perfect. But when I use UNION I get error pusd2.StartDate invalid identifier. What is wrong here ? What I made wrong ? Table

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