MySQL must know and know -- Chapter 16 creating advanced connections

Create advanced join This chapter will explain some other join types (including their meaning and usage), and introduce how to use table aliases and aggregation functions for the joined tables. Use table alias Chapter 10( MySQL must know and know -- Chapter 10 creating calculation fields )Describes how to use aliases to reference table colum ...

Posted by NathanLedet on Thu, 27 Jan 2022 19:54:49 +0100

Summary of sql statements and common functions in Oracle

sql and functions commonly used in oracle TO_DATE, EXISTS, CASE... WHEN functionLISTAGG function and OVER PARTITION BY functionFind out whether a value exists in the whole database in Oracle databaseoracle sql statement specification, creating columns, adding columns, deleting columns, functions, etcFunction that returns the time difference b ...

Posted by bradsteele on Thu, 27 Jan 2022 19:06:38 +0100

MySQL database learning log: database overview and SQL language foundation

MySQL database Database overview Database related concepts DB Database: it is "a warehouse that organizes, stores and manages data according to data structure". Is a long-term storage in the computer, organized, shareable, unified management of a large number of data collection. It is essentially a file system, which exists on ...

Posted by nerotic on Thu, 27 Jan 2022 04:03:59 +0100

Java SQL Inject/XSS/SSRF

Java SQL Inject JDBC SQL Inject If the JDBC native query is not precompiled but directly spliced with SQL statements, then the filtering is not strict, which will cause SQL injection problems. For example, the following code is a Demo with SQL injection vulnerabilities Class.forName("com.mysql.cj.jdbc.Driver"); Connection conn = DriverManage ...

Posted by sufian on Thu, 27 Jan 2022 02:38:09 +0100

DQL related operations

-DQL operation table record - query [ key ] 7.1 basic query syntax select Field name to query from Table name [where condition] 7.2 simple query 7.2.1 query records of all rows and columns grammar select * form surface Query all the columns in the commodity table select * from product; 7.2.2 query records of specific columns in a t ...

Posted by markmuir on Thu, 27 Jan 2022 00:36:37 +0100

Super hard core learning manual series 1 - explain the knowledge points of MySQL in simple terms, which is necessary for learning and collecting

I am participating in the CSDN "new programmer" award-winning essay solicitation There are thousands of people in the vast sea. Thank you for seeing here this second. I hope my article will help you! May you keep your love and go to the mountains and seas in the future! 1. Basic knowledge of database 1.1 why learn database ...

Posted by vargadanis on Wed, 26 Jan 2022 21:33:55 +0100

SQL retention analysis (next day retention, multi day retention) and optimization scheme for continuous active population

1. Description of index caliber Retained on the next day: the number of users who use the product on the first day and still use it on the second day Multi day retention: the number of users who use the product on the first day and still use it after many days Number of people continuously active: how many people continuously use products 2 ...

Posted by kontesto on Wed, 26 Jan 2022 21:18:10 +0100

Syntax comparison between Presto and Hive

Some time conversion problems are often encountered in work: 1) log_date:20200110 needs to be converted to standard date or compared with timestamp data 2) The working environment involves Presto and hive. It is faster to check the query with presto. Therefore, it is generally necessary to convert the date with the syntax of Presto and hive a ...

Posted by Lord Brar on Tue, 25 Jan 2022 23:31:57 +0100

CTO said, who has the following eight ways to write SQL directly

1. Introduction MySQL still maintained a strong database popularity growth trend in 2016. More and more customers build their applications on MySQL database, and even migrate from Oracle to MySQL. However, some customers encounter some problems in the process of using MySQL database, such as slow response time, full CPU, etc. Alibaba cloud R ...

Posted by ticallian on Tue, 25 Jan 2022 23:01:02 +0100

Hive interview question 25 -- Application of nested window clauses in conditional judgment statements (error prone points)

catalogue 0 demand analysis 1 data preparation 3 data analysis 4 Summary 0 demand analysis Requirements: table below user_idgood_namegoods_typerk1hadoop1011hive1221sqoop2631hbase1041spark1351flink2661kafka1471oozie108 In the above data, goods_ The type column, assuming that 26 represents advertising, now there is a demand to obtain the ...

Posted by kidbrax on Tue, 25 Jan 2022 12:22:51 +0100