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Guide: many friends analyze data for two minutes and run for two hours? In the process of using SQL, we should not only pay attention to the data results, but also pay attention to the execution efficiency of SQL statements. This article involves three parts with a long length. It is suggested to read it after collection: SQL introductio ...

Why KubernetesContainers are a great way to package and run applications. In a production environment, we need to manage the containers that run our applications and ensure that they don't go down. If one container fails, you need to start another container. If the system handles this behavior, will it be more convenient? This is the value of K ...

Basic operation of SparkStreaming in PySpark preface Stream data has the following characteristics: • data arrives quickly and continuously, and the potential size may be endless • numerous data sources and complex formats • large amount of data, but do not pay much attention to storage. Once processed, it will either be discar ...

32 please send the last of all employees in the employees table_ Name and first_name is spliced together as name, separated by a space in the middle select concat(last_name,' ',first_name) from employees; Parsing, two string connection methods: mysql CONCAT(str1,str2,...) and CONCAT_WS(separator,str1,str2,…) 33 table building crea ...

Database notes 1 1. Relationship between SQL, DB and DBMS DB: the DataBase exists as a file on the hard disk SQL: structured query language, high-level language, compiled and executed DBMS: DataBase Manager System Mysql, SQLservice, Oracle, DB2, Syba se Relationship: DBMS executes SQL statements and then operates DB data 2. Tables and g ...

Article catalogue SQL Birth of SQL Standardization SQL:2019 SQL:2016 SQL:2011 SQL:2008 SQL:2006 SQL:2003 SQL:1999 SQL-92 Language characteristics Statement classification SQL realization NewSQL The birth of SQL It was a summer in ...

preface Recently, the teacher of computer class has gone through [database establishment and maintenance], [database table and index creation], [single table query] and [multi table query], but his mind is still messy, so he sorted out this note for future sorting and review. The main content is the query of single table and multi table. ...

1. Introduction to data: Tianchi Taobao User Data 2. Data Import and Cleaning SQL interface tool used this time - SQL workbench 2.1 Importing data create table userbehavior( userID int, itemID int, categoryID int, bahaviortype text, timestamp int ); load data infile "C:/ProgramData/MySQL/MySQL Server 8.0/Uploads/UserBehavior.csv" into ta ...

This article was written because of a recent need: Known field values for a table are irregular comma-separated strings with the following styles: Now split the field into four fields by comma with the following styles: I have not had a ready-made function in Baidu for a long time, so I can only think of my own way. First of all, the simplest ...

Chapter 48 SQL function DAYOFMONTH Date function that returns the month date of a date expression. outline {fn DAYOFMONTH(date-expression)} parameter Date expression - the date or timestamp expression from which to return the month value date. An expression that is a column name, the result of another scalar function, or a date or tim ...