2024
Optimizing a data lake on AWS S3 with Athena and Glue Data Catalog involves several best practices to ensure data is efficiently stored, queried, and managed. The combination of S3 for storage, Glue for data cataloging, and Athena for querying Read more…
Source for problem:https://www.interviewquery.com/questions/user-experience-percentage?via=venkata&ref=venkata my solution :
n PostgreSQL, partitioning means dividing a large table into smaller, more manageable pieces, called partitions, but they all act as part of a single logical table. These partitions are physically separate from each other on disk, which helps optimize performance Read more…
Amazon Redshift does not support native table partitioning in the same way as databases like PostgreSQL or Oracle. However, Redshift provides alternative methods to achieve similar performance benefits as partitioning, primarily through sort keys and distribution styles. These allow for Read more…
Amazon Redshift materialized views do not automatically refresh when the underlying data changes. You need to manually refresh the materialized view to keep the data up to date. How to Refresh a Materialized View To refresh the data in a Read more…
URL :https://dataford.io/sql/Population-Density-Analysis To get the maximum and minimum densities globally and sort cities by their density, you can use a subquery or a CTE as previously suggested. Here’s a step-by-step correction: approach two: explanation Population Density Calculation: The ROUND(population / Read more…
2024
In the query provided for NTH_VALUE, don’t you need to include employee_name in a GROUP BY clause ?No, because you are using a window function and not performing aggregation that requires grouping. Window functions operate over a set of rows Read more…
2024
Analytic Functions: a. LAG() b. LEAD() c. FIRST_VALUE() d. LAST_VALUE() E.NTH_VALUE() These examples use the sales and employee tables to show how window functions can be applied with multiple tables to provide context and derive meaningful insights
2024
Let’s incorporate both tables (sales and employee) into the examples for window functions. We’ll use sales to show the data and apply window functions, and employee to provide additional context like employee names. Sample Data Table: sales Window Functions with Read more…
When learnig SQL at the beginig it may look like more complcated and confused , because when to use this window functions and whether do we need use GROUP BY satment for each of slected fileds .So here im going Read more…