---------------------------------------------------------------Table building----------------Determine whether the student table exists
declare num number; --Declare parameters num type number
select count(1) into num from user_tables where table_name='student';
if num>0 then
execute immediate 'drop table st ...
Added by crinkle on Thu, 21 May 2020 18:21:15 +0300
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Python has a lot of map visualization libraries. Although Matplotlib library is very power ...
Added by dannyluked on Thu, 21 May 2020 09:54:45 +0300
1. After getting the user name, password and authentication code in the background:
(1) Get the data submitted by the form
(2) Determine whether the verification code is correct or not
If the verification code is correct:
1. Encrypt the password in the form by MD5 MD5 moduleHttps://www.npmjs.com/package/md5
1,install cnpm install md5 --sav ...
Added by jjoves on Wed, 20 May 2020 20:28:13 +0300
JDBC fixing steps:
Class.forName("com.mysql.cj.jdbc.Driver");//I don't know why com.mysql.jdbc.Driver will report an error. Please leave a message if you have any ...
Added by PHPfolife on Wed, 20 May 2020 17:31:54 +0300
In recent years, the business of leader 1-to-1 has been developing rapidly, but at the same time, he has encountered "growing pains". With the increasing number of microservices, the traffic further increases, and the hardware resources are a little overwhelmed. Then, how to achieve better flow protection measures such as curr ...
Added by webtailor on Mon, 18 May 2020 09:32:34 +0300
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
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
Added by brighton on Thu, 14 May 2020 12:11:49 +0300
The main application scenario of redis multiple data sources is to use multiple redis servers or multiple redis libraries. In this paper, the fastdep dependency integration framework is used to quickly integrate redis multiple data sources and integrate lettuce connection pool. Only after introducing dependency, configure th ...
Added by hitman6003 on Wed, 13 May 2020 16:46:01 +0300
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
Original address: https://mysqlserverteam.com/mysql-8-0-innodb-now-supports-instant-add-column/
For a long time, instant DDL has been one of the most popular InnoDB functions. For the growing and fast-growing data set, any network scale database must have the function of executing DDL immediately.
Developers often need to add new columns to m ...
Added by coolfool on Tue, 12 May 2020 16:55:02 +0300