sql learning micro course on kaggle website
catalogue
Start sql journey
Exercise 1: count the number of tables in the dataset
Exercise 2: explore the summary of the table
Exercise 3: create a crime map
Select/From/Where simple query
Exercise 1: identify countries that use ppm
Exercise 2: select * query all fields
Group by&Having&Count
Exercise 1: find out the a ...
Posted by bex1111 on Wed, 15 Sep 2021 02:27:04 +0200
Base Query, Conditional Query, Sort Query for Database 03-DQL Data Query
Base Query
1. Grammar
The select query list from table name is similar to System.out.println (print stuff)
2. Characteristics
1. Query lists can be: fields in tables, constant values, expressions, functions 2. Query results can be a virtual table
3. Examples
1. Query a single field: select field name from table name;
2. Query multipl ...
Posted by keenlearner on Fri, 10 Sep 2021 06:39:55 +0200
SQL statement basic exercise (table creation, basic query) - Provide table building statements and query topics and answers
Explain
The difficulty of the basic exercises is fairly simple, but there are still some details to master. The main purpose of this topic is to familiarize yourself with the basic queries of SQL statements, so you can understand the statements about table building, because in general development, tables are built graphically, while SQL sta ...
Posted by jjfletch on Tue, 07 Sep 2021 23:40:42 +0200
Notes on MyBatis2
Important notes about MyBatis2 are in the following Baidu network disk connection. Welcome to learn together Link: https://pan.baidu.com/s/1zGAtbdQElMTgzUZUSg033w Extraction code: 2ywn
Here are some easily forgotten points in my learning process to make another record for follow-up review
Step 1: write mybatis configuration file
<?xml ver ...
Posted by verlen on Tue, 07 Sep 2021 23:01:06 +0200
Berserker says Mybatis notes
Crazy God said MyBatis01: the first program
Introduction to MyBatis
Environmental description:
jdk 8 +MySQL 5.7.19maven-3.6.1IDEA
Before learning, you need to master:
JDBCMySQL
Java Foundation MavenJunit
What is MyBatis
MyBatis is an excellent persistence layer frameworkMyBatis avoids almost all JDBC code and the proce ...
Posted by jeephp on Thu, 02 Sep 2021 20:47:51 +0200
ajax and servlet -- Verify that the user name exists
Verify that the user name exists -- using jQuery
1. Database mysql
The user name already exists in the database.
2. html Page
<body>
<h1>User Login</h1>
<hr>
<form name="regForm" action="dologin.jsp" method="post">
<table>
<tr>
<td>user ...
Posted by splitinfo on Fri, 17 Jul 2020 16:26:13 +0200
Solution with empty list in foreach tag in Mybatis
In the previous article Optimizing Mybatis in-query through interceptor Interceptor In, we have resolved the case of an empty in() list in the mybatis query.
However, because the list in the foreach tag is empty, not only is an in() empty list, but another common situation occurs when data is inserted in batches, as follows:
INSERT INTO table1( ...
Posted by eurozaf on Mon, 13 Jul 2020 17:30:03 +0200
Three ways of querying hibernate
There are three main query modes common to hibernate: HQL, QBC (named query), and using native SQL query (SqlQuery)
HQL Query
* HQL (Hibernate Query Language) provides a rich and flexible way of querying, and using HQL for querying is also Hibernate's official recommended way of querying.
* HQL is very similar in syntax structure to ...
Posted by DavidT on Fri, 10 Jul 2020 17:19:12 +0200
django implements foreground and background data binding by submitting form with ajax+post
The first step is to introduce jquery files, either online or offline, to add to your own staticfiles
What's demonstrated here is adding offline
<script src={% static 'js/jquery-2.1.1.min.js' %}></script>
Note that this sentence is added before the ajax jquery script you write.
Then the HTML form is as follows:
...
Posted by TraceyK on Tue, 07 Jul 2020 16:31:40 +0200
Prompt access_when timed task is executed in micro messageToken invalidation (short note)
Scenario reproduction: The timer task is working, but when the timer function executes regularly, the error message access_is printed in the logToken fails (or cannot be obtained, etc.), access_in the test tableToken is 0; access_is available when you directly access a link to a timer function yourselfToken.
Reason: When I execute by myself, ...
Posted by bobthebuilder on Mon, 06 Jul 2020 17:24:30 +0200