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Articles by Select Case
해커랭크 - Basic (SQL)
Weather Observation 8 Query the list of CITY names from STATION which have vowels (i.e., a, e, i, o, and u) as both their first and last characters. Your result cannot contain duplicates.
ROLLUP
Understanding the Use of the ROLLUP Function in SQL The ROLLUP function is a powerful tool in SQL that allows you to generate subtotals and grand totals in aggregated queries. This feature is particularly useful for reports and analysis, where there is a need to calculate consolidated values at different levels of detail. What is ROLLUP? The ROLLUP function is used in conjunction with the GROUP BY clause to create hierarchical groupings.
Accelerate Amazon Redshift Data Lake queries with AWS Glue Data Catalog Column Statistics | Amazon Web Services
Amazon Redshift enables you to efficiently query and retrieve structured and semi-structured data from open format files in Amazon S3 data lake without having to load the data into Amazon Redshift tables. Amazon Redshift extends SQL capabilities to your data lake, enabling you to run analytical queries. Amazon Redshift supports a wide variety of tabular data formats like CSV, JSON, Parquet, ORC and open tabular formats like Apache Hudi, Linux foundation Delta Lake and Apache Iceberg.
How we built ngrok's data platform
At ngrok, we manage an extensive data lake with an engineering team of one (me!). This article is a look at how we built it, what we learned, as well as some selective deep dives I found interesting enough to be worth sharing in more detail, since they’ll bridge the gap between what people usually understand by the term “data engineering” and how we run data here at ngrok.
【mysql&算法】在数据库中储存树形结构_mysql存储树形结构-CSDN博客
【一】常见的使用树的场景 以树状结构表示和存储数据是软件开发中的常见问题： （1）XML / Markup语法解析器（例如Apache Xerces和Xalan XSLt）使用树 （2）PDF使用以下树结构：根节点->目录节点->页面节点->子页面节点。通常，PDF文件在内存中表示为平衡树 （3）多种科学和游戏应用程序使用决策树，概率树，行为树；Flare可视化库（http://flare.prefuse.org/）充分利用了生成树，经纪人在决定是否投标合同时也使用树 树是表示层次结构的方法之一，因此可用于许多问题域： （1）计算机科学中的二叉树 （2）生物学中的系统树 （3）商业中的庞氏骗局 （4）项目管理中的任务分解树 （5）树用于建模多级关系，例如“上级-下级”，“祖先-后代”，“整个-部分”，“一般-特定” 【二】方式一：邻接表...
Airbnb Data Scientist Interview Questions
This article will teach you how to solve one of the hard Airbnb data scientist interview questions Airbnb is one of the most popular companies for data scientists. It’s in the lodging and the hospitality industry. While traditionally, you wouldn’t expect this to be an industry of high interest for data scientists, Airbnb is different. And this difference, of course, reflects in the fact they operate as an online marketplace for accommodation that connects hosts and guests.
How to handle dates in SQL using in-built functions
Here are some of my staple date functions. 1. Date_trunc Date_trunc is used to truncate the date to Week, Month, Quarter, or Year. This function is most widely used for creating time series and aggregating at a granular level. For instance, this function can be used if you want to plot the trends for KPIs like Quarterly sales, active users, monthly orders, etc. Syntax: SELECT DATE_TRUNC('month',calendar_date) AS Month, COUNT(DISTINCT USER) AS active_users FROM usage GROUP BY 1 2.
增加子查询表条件筛选提高性能_ITPUB博客
前提 客户反应现场有sql很慢，故拿来优化下。 原有慢sql select case when t1.sys_id = '200000000' then '' else t1.USER_NO end user_no, t2.USERCARD, t2.NAME, t2.USERID_WEIXIN from (select * from WEIXINUSER.t_user_relation tur11 where not exists (select id from (select id from (select distinct id, sys_id from WEIXINUSER.t_user_relation where sys_id in ('100000000', '200000000') order by to_number(id)) group by id having count(id) > 1) tmp1 where tmp1.id = tur11.id) order by id) t1 left join WEIXINUSER.t_user t2 on t1.id...
How to Decipher @@Options – SQLServerCentral
There is a variable in SQL Server called @@OPTIONS. This contains all of the settings that you have configured using the SET command. However, understanding the values inside of this variable can be a bit cumbersome. This article will show you a quick way to determine what settings you have in your environment. Decoding @@Options The @@Options variable contains an integer. This integer contains the values of all the SET options. As an example, I can run this: What does this mean?
5 Tricky SQL Queries Solved
Sql vector created by freepik - www.freepik.com SQL(Structured Query Language) is a very important tool in a data scientist’s toolbox. Mastering SQL is not only essential in an interview point of view, but a good understanding of SQL by being able to solve complex queries will keep us above everyone in the race. In this article, I will talk about 5 tricky questions I found and my approaches to solve them. We are given a table consisting of two columns, Name, and Profession.
Using Mod to Generate Work Shifts – SQLServerCentral
I am by no stretch a SQL expert but writing queries to retrieve and manipulate data is one of the more enjoyable tasks I get to work on. And one of my favorite aspects about writing queries is that there are a number of ways to accomplish the same task. With some being more effecient than others depending upon the situation Bit of Background I was working for a city doing work for their fire department.
Hive SQL Dynamic Column Retrieval
Explore Hive SQL techniques for dynamic column retrieval in sequence-to-sequence models, enhancing data manipulation and analysis. The framework for autonomous intelligence Dynamic column retrieval in Hive SQL allows users to access and manipulate data in a flexible manner, adapting to varying schema structures and data types. This capability is particularly useful when dealing with complex datasets where the schema may not be explicitly defined or may contain ambiguous column names.
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