C ා data operation series - 7. EF Core navigation attribute configuration

In the previous article, I introduced the logic of relationship mapping in Entity Framework Core. The foreign key mapping of EF left in the previous article is not mentioned, that is, the relationship of one-to-one, one to many, many to one, many to many, etc. This article will give you a detailed analysis of how to set up these mappings. 1. Re ...

Added by imawake on Sun, 17 May 2020 08:59:50 +0300

MySQL database functions

1, Date and time functions 1. Function to get the current dateIt's the same. It's different CURDATE() : Used to get the current date of the system CURRENT_DATE() Used by the system to get the current date mysql> select CURDATE(),CURRENT_DATE(); 2. Get function of current time CURTIME() : Used to get the current time of the system mysql& ...

Added by brighton on Thu, 14 May 2020 12:11:49 +0300

Issue 04: column CHECK constraint

check constraint means to filter one or more columns according to certain preset rules. If the condition is true, the filtering succeeds; if the condition is false, the filtering fails and the failure code is returned to the client. Why do you want to list and write this separately? You often encounter irregular SQL. In many cases, you can onl ...

Added by AndyB on Wed, 13 May 2020 12:25:22 +0300

My first JDCB program

1, Create your own database Download and install MySQL 1.windows Download: http://dev.mysql.com/downloads/mysql/ 2. Open the server: enter the bin directory of the download path in the terminal (cmd), and execute mysqld -- initialize executor to start the server and initialize, but an error will be reported. The reason is that there is no data ...

Added by _giles_ on Mon, 11 May 2020 07:51:35 +0300

Database learning 7: MySQL client tools and SQL introduction

7, MySQL client tools and SQL introduction 1. Syllabus: mysql client command introduction; How to get help from mysql; Management database of DDL statements; DDL statement management table and case introduction; Data in management table of DML statement; SELECT to retrieve data; 2. mysql interface program and SQL introduction mysql client comma ...

Added by jdimino on Fri, 08 May 2020 16:47:04 +0300

Using Blink SQL+UDAF to realize difference aggregation calculation

According to the real business requirements of a power grid company, this case realizes the difference aggregation calculation on the real-time flow through Blink SQL+UDAF. Through this case, the readers are familiar with UDAF writing and understand the method invocation relationship and order in UDAF. Thank you @ commander for your guidance in ...

Added by stalione on Fri, 08 May 2020 12:15:27 +0300

[2020Python cultivation] MySQL view, trigger, transaction, stored procedure and function

[contents] (the rest are knowledge) A view Two triggers Three Affairs (mastery) Four stored procedures Five functions Vi. process control 7, Index theory   1, View 1. What is a view A view is a virtual table (non real existence). Its essence is to get a dynamic data set according to SQL statements and name it. When users use it, they only ne ...

Added by csplrj on Fri, 08 May 2020 11:46:25 +0300

Computer room charging system (2)

The charge system in the computer room is half developed. From blind helplessness at the beginning to being able to proceed slowly now, it is a small progress. The basic data setting window in the computer room charging system is a very important window in the whole software. When I open the database software, I see that there are many pieces o ...

Added by aquilla on Wed, 06 May 2020 03:28:31 +0300

Oracle+Mybatis bulk insert, update and delete

1. Insert (1) The first way: use < foreach > tag to generate virtual data through UNION ALL for the list set of incoming parameters, so as to realize batch insertion (verified)   1 <insert id="insertBatchLaTContactRecord" parameterType="java.util.Map"> 2 <selectKey resultType="java.lang.Long" keyProperty="dto.id" order="BE ...

Added by halex on Tue, 05 May 2020 14:32:13 +0300

Enum, generics, reflection, JDBC integration

brief introduction Environmental preparation Project directory jar package used Database connection configuration JDBC configuration file Run tests brief introduction JDBC (Java database connectivity) is a Java API used to execute SQL statements. It can provide unified access to a variety of relationa ...

Added by asdf on Sun, 03 May 2020 15:38:15 +0300