Selva Prabhakaran

Problem You need to retrieve a list of dates between two specified dates. Input First, let’s create a table and insert some sample data into it. startDate endDate 2023-01-01 2023-01-05 2023-02-01 2023-02-03 For this example, the table contains two date ranges: Jan 1 to Jan 5 and Feb 1 to Feb 3 of 2023. Try …

How to get a list of dates between two dates in SQL? Read More »

The difference between CROSS JOIN and INNER JOIN in SQL The question here is about the difference between a CROSS JOIN and an INNER JOIN in SQL. While both can be used to combine rows from two or more tables, they do so in distinct ways: CROSS JOIN: Combines each row of the first table …

What is the difference between CROSS JOIN and INNER JOIN in SQL? Read More »

Problem You have two tables, tableA and tableB. You want to retrieve all records from tableA that do not have a matching record in tableB based on a specific column. Input Let’s start with creating two tables and populating them with data. tableA – This will be our primary table where we’ll select data from. …

How to get records from one table that does not exist in another? Read More »

Problem How to access the “previous row” value in a SELECT statement in SQL? Input id sale_date units_sold 1 2023-01-01 10 2 2023-01-02 15 3 2023-01-03 12 4 2023-01-04 20 Try Hands-On: HERE Source Tables: Gist Desired Solution sale_date current_day_sales previous_day_sales 2023-01-01 10 2023-01-02 15 10 2023-01-03 12 15 2023-01-04 20 12 Solution 1: To …

How to access the “previous row” value in a SELECT statement in SQL? Read More »

Problem You have a database table, how to select all columns except specific columns mentioned by the user? Example Syntax: SELECT * [except columnA] FROM tabA; Input id first_name last_name email salary 1 John Doe [email protected] 50000 2 Jane Smith [email protected] 60000 3 Bob Brown [email protected] 55000 This is not possbile in native SQL databases. …

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Problem Let’s understand the difference between UNION and UNION ALL in SQL with an example. Input Let’s create a table named fruits with columns id, name, and type. We will insert some rows into this table: id name type 1 Apple Fresh 2 Banana Fresh 3 Apple Dried 4 Banana Dried 5 Cherry Fresh Try …

What is the difference between UNION and UNION ALL in SQL? Read More »

Problem Let’s see how to find duplicate values in an SQL table. Input id name enrollment_number 1 Alice ENR123 2 Bob ENR124 3 Charlie ENR125 4 David ENR123 5 Edward ENR126 6 Frank ENR124 Try Hands-On: Fiddle Create Source tables: Code Gist Desired Output enrollment_number count ENR123 2 ENR124 2 Solution 1: Using GROUP BY …

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