Entity Framework Core series tutorial-3 generating entity model for existing database

Create a model for an existing database in the Entity Framework Core Here, you will learn how to create context and entity classes for existing databases in the Entity Framework Core. Creating entity and context classes for an existing database is called the database first method. EF Core does not sup ...

Posted by UQKdk on Fri, 07 Feb 2020 06:08:09 -0800

JDBC operation database and difference among statement, preparedStatement and callableStatement

The database can be operated easily by Java using JDBC API. In java8 and later, JDBC ODBC bridge connections have been dropped. For different databases, download the driver to the corresponding official website. Here are three common database driver names, driver class and corresponding connection strin ...

Posted by spiceweasel on Fri, 07 Feb 2020 01:45:48 -0800

MySQL Database - Functions, Transactions, Indexes, Rights Management and Backup, Specifications for Databases

1. MySQL functions Official website: https://dev.mysql.com/doc/refman/5.7/en/func-op-summary-ref.html 1.1. Common Functions -- ==================== Common Functions ============================= -- Mathematical operations SELECT ABS(-8) -- absolute value SELECT CEILING(9.4) -- ceil SELECT FLOOR(9. ...

Posted by undecided name 01 on Wed, 05 Feb 2020 20:01:33 -0800

MongoDB series -- Aggregate pipeline operation in SpringBoot

MongoDB pipeline definition The aggregation pipeline of MongoDB will pass the results of MongoDB documents to the next pipeline after one pipeline is processed. Pipeline operations are repeatable. Common Aggregate pipeline operators of Aggregate in SpringBoot Customize the collection userCollection and initialize the data structure Store bean u ...

Posted by adnan856 on Wed, 05 Feb 2020 07:50:14 -0800

JDBC development steps

JDBC development steps 1. Registration driver ---Tell the JVM which database driver to use 2. Get connected ---Use the classes in JDBC to complete the connection to the MySQL database 3. Get statement execution platform ---Get the executor object of the SQL statement through the connection object ...

Posted by scross on Wed, 05 Feb 2020 06:10:11 -0800

ProcessFunction: the lowest level API of Flink

Some operators and functions mentioned above can perform some time operations, but cannot obtain the current Processing Time or Watermark timestamp of the operator, which is simple to call but relatively limited in function. If you want to get the time stamp of Watermark in the data flow, or shuttle bac ...

Posted by eddjc on Wed, 05 Feb 2020 02:21:22 -0800

Unexpected formatting time with Calendar

Java8 Chinese Documentation: http://www.matools.com/api/java8 java8 LocalDate Reference: https://www.journaldev.com/2800/java-8-date-localdate-localdatetime-instant Background: Time sections are formatted where deadlines are involved, such as the start and end times of events (2019-11:00:00~2019-11 ...

Posted by Altairzq on Tue, 04 Feb 2020 19:27:29 -0800

SqlServer uses cursors to update data in batches

Intro Cursors can be very useful sometimes. When updating a small part of data, they can easily update the data. There is no need to write another small tool to do this, just write SQL directly Sample Here is a practical example: -- Declare field variables DECLARE @RegionCode INT; DECLARE @RegionName NVARCHAR(64); DECLARE @ProvinceId INT; -- d ...

Posted by shock on Tue, 04 Feb 2020 10:02:03 -0800

ORM aggregate function details: Count

Count: used to find the number of data. The model used in all of the following examples is: from django.db import models # Define author model class Author(models.Model): name = models.CharField(max_length=100, unique=True) age = models.IntegerField() email = models.EmailField() c ...

Posted by digitalalpha on Mon, 03 Feb 2020 05:59:44 -0800

Find the number of adjacent words in large amount of data

This topic is similar to some of the search topics in Leetcode. The problem you want to deal with is: count the number of two adjacent digits of a word. If there are w1,w2,w3,w4,w5,w6, then: The final output is (word,neighbor,frequency). We implement it in five ways: MapReduce Spark Spark SQL method Scala method Spark SQL for Scala MapReduce ...

Posted by olechka on Sun, 02 Feb 2020 08:18:59 -0800