Flexible use of Spark window functions lead and lag for online time length statistics

brief introduction In data statistics, it is often necessary to count some time-consuming data, such as online time. Some of these data are better to count, and some are a little bit more troublesome. For example, count the online time of users according to the log in and log out. We can use the window functions lead and lag to complete, which ...

Posted on Tue, 09 Jun 2020 23:56:54 -0400 by dpiland

Introduction and Practice of SQL Functions for PostgreSQL

RDBMS, as a safe, shared and reliable software management system for managing data, needs to organize and store data according to different data models. In order to facilitate the processing of data for users, any database provides rich processing functions for different data types in order to simplify the complexity of business development.In ...

Posted on Tue, 09 Jun 2020 13:50:47 -0400 by mjgdunne

Flink Sql on Zeppelin -- environment preparation

Environmental preparation summary Why Sql At present, there are many ways to develop Flink. Generally speaking, students write JAVA/SCALA/PYTHON projects and submit them to the cluster for running This method is more flexible, because you can write tasks in the code. Any dimension table JOIN and ...

Posted on Mon, 08 Jun 2020 22:13:41 -0400 by Dave Liebman

MongoDB Quick Start, that's all right!

SpringBoot e-commerce project mall (30k+star) address: https://github.com/macrozheng/mall abstract Although relational databases are still the mainstream now, it is necessary to learn a mainstream NOSQL database to supplement them when facing some requirements.MongoDB is a rich NoSQL database. This introductory tutorial is organized from its m ...

Posted on Mon, 08 Jun 2020 21:26:03 -0400 by d_priyag

SQL, reading notes, MySQL must know

This is MySQL must know must know [1] Reading notes are used to summarize knowledge points and framework. They are only for reference and exchange. Please contact us if you have any problems. As the software version is updated, some codes in the book are no longer applicable. This paper mainly deals wit ...

Posted on Sun, 07 Jun 2020 04:26:29 -0400 by renegade33

Printing and design of C ා label (bar code)

The last article talked about barcode printing, mainly through reading the template definition file (XML file), and then combining the dynamic data read from the database to generate barcode. Here is how to design the barcode template. The design process is also very simple, just a simple drag. Then click the small arrow or the command in the l ...

Posted on Sun, 07 Jun 2020 04:04:26 -0400 by tim

Where PL/SQL stored procedures can go wrong with IDEA use [High energy ahead!]

Stored procedures in PL/SQL combined with IDEA 1. What are stored procedures? A named PL/SQL block stored in a database that is a type of database object that an application can call to execute logic.   2. Grammar: create [or replace] procedure Stored procedure name --Three parameter modes: -- IN Incoming parameter (default, can ...

Posted on Sat, 06 Jun 2020 12:41:23 -0400 by Daguse

Understand MYSQL in one day

MySQL learning notes Installation tutorial: https://www.runoob.com/mysql/mysql-install.html Install video: https://www.bilibili.com/video/BV1HK41157k8?from=search&seid=8785963740363848969 Log in and log out of MySQL server # Log in to MySQL $ mysql -u -p # Exit MySQL database server exit; B ...

Posted on Sat, 06 Jun 2020 02:34:07 -0400 by nwp

MySQL stored procedure writing guide

introduction Because of too many labels, the structure of label table has been changed in the actual application process. From the past, we can choose labels at will. Now we need to classify labels to simplify the difficulty of selection. After adding account classification, you need to add account information to the labels that have been used ...

Posted on Sat, 06 Jun 2020 00:25:42 -0400 by malec

Summary of Java Concurrent Programming Practice

premise First, the scene is a hotel-based business.I simplified my business for friends to read easily. Business: After opening a room, a bill will be added, and a room schedule record will be added. The room schedule is mainly for the time used in the room to be non-conflicting.For example: Bill A, use Room 1, use period of time is 220-06-01 1 ...

Posted on Fri, 05 Jun 2020 22:12:46 -0400 by isaacsf