Are MySQL Join statements inefficient?

We often hear Join join queries that avoid using MySQL because of poor performance. Is this the case?Let's try it out. 1. Environment MySQL: 5.7.30 Storage Engine: InnoDB Index type: default optimized B+tree   2. Prepare 2.1 Table preparation and data preparation We plan to create five tables and insert 10W pieces of data into them, ...

Posted on Tue, 02 Jun 2020 07:53:10 -0400 by hanpedro

Oracle learning - view, sequence, synonym, index

1. View 1.1 what is a view View is a mapping of virtual table and entity table. When to use views In development, there are some table structures that do not want too many people to contact, so entity tables are mapped to a view. (simplified table structure) In the project process, programmers mainly focus on the performance of coding and ...

Posted on Mon, 01 Jun 2020 11:55:47 -0400 by ldtiw

type column parsing of explain

1,const Indicates that the execution step returns at most one row of data. const usually appears in the equivalent query of the primary key or unique index, such as the equivalent query of the primary key id of the t table:It can be considered that it is as fast as a rocket to locate a record by comparing the equivalence between the primary key ...

Posted on Sun, 31 May 2020 11:54:35 -0400 by peter_anderson

Summary of JDBC basic knowledge

Refer to the summary of Java language programming foundation version 10 Main interface 1 Basic JDBC program 2. The main methods of initializeDB and showGrade are to access the database from JavaFX Statement 1PreparedStatement interface inherits from Statement interface to create parameterized SQL Statement Exa ...

Posted on Sun, 31 May 2020 04:35:47 -0400 by cpharry

Access to byte stream of sqlite byte array

There are two ways to store sqlite byte arrays: It's easy to understand how to store byte array in string type Base64.encodeToString(rawData, Base64.DEFAULT) byte[]Convert to string Base64.decode(printData.getBytes(), Base64.DEFAULT) string Convert to byte[] The data type of the specified field is blob BLOB - The value is a blob of data, ...

Posted on Sun, 31 May 2020 01:45:55 -0400 by lutzlutz896

Access to byte stream of sqlite byte array

There are two ways to store sqlite byte arrays: It's easy to understand how to store byte array in string type Base64.encodeToString(rawData, Base64.DEFAULT) byte[]Convert to string Base64.decode(printData.getBytes(), Base64.DEFAULT) string Convert to byte[] The data type of the specified field is blob BLOB - The value is a blob of data, ...

Posted on Sun, 31 May 2020 01:38:33 -0400 by Holoverse

How to use Apache Flink to query Pulsar flow

In the previous blog, we introduced Apache Pulsar and its differences from other message systems, and explained how to integrate Pulsar and Flink to work together to provide a seamless developer experience for large-scale elastic data processing.   This article will introduce the integration and latest research and development progress of Apa ...

Posted on Sat, 30 May 2020 02:54:34 -0400 by pck76

A single example of PHP PDO and mysql connection to prevent timeout

This database class mainly deals with creating database objects in single instance mode. If there are two long-time intervals to execute sql operations, the problem of connection failure will occur when processing again. A cache array is used to store pdo objects and timestamps, and the time between the two executions is compared. If the interv ...

Posted on Fri, 29 May 2020 04:02:35 -0400 by kaveman50

C ා data operation series - Introduction to 19 FreeSql

0. Preface The author of FreeSql recommended the FreeSql framework to me a few days ago. I want to help write an article about it. Well, I can't believe I can bring a product. Ha ha, I'm joking. I think it's very interesting after reading it, so I thank you for this article. Briefly, FreeSql is a sandbox level project organized by NCC. It is ...

Posted on Fri, 29 May 2020 01:40:19 -0400 by simply

PHP regular expression details how to extract characters between two strings (supports single & multiple)

preface: Sometimes it is necessary to extract some characters from a long string, which is often used for variable query and replacement. Scenario: If I have a hive SQL statement, I need to replace the variable {@ date} with a specific date, such as 20200526, select "F" as sex, c.moviename as name, avg(a.rate) as avgrate, co ...

Posted on Wed, 27 May 2020 10:49:36 -0400 by ts2000abc