Database
Database
Top 10 Databases You Should Learn in 2020
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A database is must need for any software development and which database to choose is one of the main requirement for software architecture. In...
Programming Jokes
MongoDB vs MySQL
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A database is a collection of information that is organized so that it can be easily accessed, managed and updated. Depending upon the usage requirements, there are...
Database
Customers Who Never Order
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Suppose that a website contains two tables, the tableCustomers and the tableOrders. Write a SQL query to find all customers who never order anything.
Table:...
Programming Jokes
Employees Earning More Than Their Managers
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The Employee table holds all employees including their managers. Every employee has an Id, and there is also a column for the manager Id.
+----+-------+--------+-----------+
|...
Database
Delete Duplicate Emails
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Write a SQL query to delete all duplicate email entries in a table named,Person keeping only unique emails based on its smallestId.
+----+------------------+
| Id | Email...
Database
Rising Temperature
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Given a Weather table, write a SQL query to find all dates' Ids with higher temperature compared to its previous (yesterday's) dates.
+---------+------------+------------------+
| Id(INT) | Date(DATE) |...
Database
Department Highest Salary
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The Employee table holds all employees. Every employee has an Id, a salary, and there is also a column for the department Id.
+----+-------+--------+--------------+
| Id | Name...
Database
Swap Sex Field
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Given a table salary, such as the one below, that has m=male and f=female values. Swap all f and m values (i.e., change all f...
Database
Combine Two Tables
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Table: Person
+-------------+---------+
| Column Name | Type |
+-------------+---------+
| PersonId | int |
| FirstName |...