Method 1:
distinct
select count(distinct CName) from Course
Method two:
Using grouping group by
select count(1) from Course group by CName
Topic gate
The main idea of the topic is:
Given n n n n 01 strings, let you construct a string so that the strings and the similarity between these strings as low as possible. If the two strings correspond to the same position, the similarity degree is increased by one.
Ideas:
You can get any 01 strings after changing each part of the 01 string. I want all strings to end up in the same 01 string. We will change the meaning of the question to make the highest degree of similarity as low as possible, that is, to make the lowest degree of dissimilarity as high as possible, and each 01 string cha...
Paper:Working hard to know your neighbor’s margins: Local descriptor learning loss
Why to introduce this article: This 2018cvpr article is mainly from the difficult sample, proposed a loss, simple but effective, in image matching, retrieval, Wide Baseline stereo, and so on have doneExtensive detailed experiments,In real tasksrealThe result of state-of-the-art is obtained. Code: https://github.com/DagnyT/hardnet. The papers in the last blog can be combined with this, and it will be better to read together. In addition, these are obtained through learn.Descriptor is not popular in practic...
1. The power supply socket of the oscilloscope must be a tripod socket, and it must be grounded reliably. In the absence of grounding wire, the power supply plug of the oscilloscope should pay attention to dividing the zero line and the fire line when it is connected, and the probe grounding wire of the oscilloscope should not be charged at one end.
Two, when testing the signal on the line, it is necessary to connect the ground wire probe before measuring the information. Because without first addressing, the probe may be electrified and damage the test element.
https://github.com/Sage-Bionetworks/BridgeResearcherUI.git
Introduction to database
1concept
3 relational database in Song Dynasty (pure theory)
Relational database is the use of Microsoft Corp)
noSQL
MangoDB,Redis
5sqlbrief introduction
Structure Query Language >:
client partmysql.exe” document, the operating environment iscmd > port number-u localhost” means the machine. 127.0.0.1” means the machine. If it is the machine, it can be omitted.
-P default, it can be omitted.
-u >root
DB DataBase ( corresponds to the form in reality.)
Record
>.
> Library option.
explains:
> is used to set the stored character...
recursive directory generator mode, else in the TMPShow that getting yield is indispensable, and if you want to use a generator in a recursive algorithm, you need to explicitly get all yield values in the generator’s original function (first call)
def get_file_recur(path):
children = os.listdir(path)
for child in children:
qualified_child = os.path.join(path,child)
if os.path.isfile(qualified_child):
yield qualified_child
else:
tmp = get_file_recur(qualified_child)
for item in tmp:
yield item
for file ...
HibernateIt is a high-performance object relational persistent storage and query service.
1. What is Hibernate?
1、Hibernateconcept
HibernateIt is the framework of data access layer and encapsulates JDBC. It is an object-oriented solution for data access.
2、HibernateRole
Hibernate can directly access objects, and Hibernate automatically converts this access to SQL execution, thus achieving the purpose of indirect access to the database and simplifying the data access layer code.
Two, why use Hibernate?
1、HibernateComparison with JDBC
1)The use of JDBC has the following disadvantages:
-...