The main difference 1.HTTPS and HTTP as follows:
1, https protocol ca need to apply for a certificate, generally less free certificates, thus requiring a fee.
2, http is the hypertext transfer protocol, information is transmitted in the clear, https is encrypted with a security ssl transfer protocol.
3, http and https use is completely different connections, with the port are not the same, the former is 80, which is 443.
4, http connection is very simple, is stateless; is constructed by the HTTPS protocol SSL + HTTP encrypted transmission protocol, a network authentication protocol, the http protocol than security.
2. The joint index, the leftmost matching principle
index on multiple fields simultaneously established (sequential, ABC, ACB are two completely different joint index.)
Why
In joint index (a, b, c) to build such an example have an index corresponding to the index a, ab, abc three indexes. An index top three indexes of course is a good thing, after all, each one more index, will increase the cost of write operations overhead and disk space.
Leftmost matching principle. (A, B, C) so that three, mysql will first match A, then B, C.
If (B, C) to retrieve such data, it would not find such that A failure index. If (A, C) to retrieve such data, it would first find all the values of A and C match, at this time the index is combined failure.
- B-Tree and B + Tree distinction:
the B + Tree, all the nodes are in accordance with the key-data records stored in the order of the leaf nodes of the same level, not only stores the key value of the leaf node information, which can greatly increase the number of key values stored at each node, the reduced height + Tree B.
4.shell + awk acquiring a file and the third column of data deduplication
awk '{ print $3 }' ws.log > temp.log
sort -n temp.log | uniq
The three left join jargon clearly explained thoroughly, and the difference between right join the inner join
popular talk:
left to left side of the main table left join tables
right table to the right of the main right join table
data lookup inner join is about two a total of table
- Linux view the port
netstat -nap kill -9 4394
7.MySSQL Article inquiry to Article X of the data
select top 10 * from TB1 where Id not in (select top 5 Id from TB1)
8. The difference between the interface and the abstract class
1. ordinary methods abstract class, no interface
2. abstract class members can have their own properties and methods, only public interfaces constant.
3. dispensable abstract class constructor, no interface constructor
9. Requests to you about socket programming server and client use which functions primarily
based on TCP socket:
1, the server program:
1 Create a socket, a function socket ()
2 binding information IP address and port to the socket, a function bind ()
3 allows the maximum number of connections is provided with functions, listen ()
4 receives client connections served by the function accept ()
5 send and receive data, a function send () and the recv (), or a read () and write ()
6 off a network connection
2, the client program:
1 Create a socket, a function socket ()
The other two properties set to connect to IP addresses and ports, etc.
3 connected to the server, using the function connect ()
4 send and receive data, a function send () and the recv (), or a read () and write ()
5 Close network connection
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