programmer group

Mysql, sqlserver and Oracle specify the number of returned records

Recently, new contacts with SQL server and Oracle database found that the total number of specified return records is actually different from mysql Mysql:select XXX where XXX limit N Sqlserver: select TOP N XXX Oracle:select XXXX where rownum < (N+1) Note: In Oracle, rownum = n, only n = 1 is true, others are false. Therefore, if n records need to be returned, the condition should bewhere rownum < (N+1) For the...

programmer group

How to increase the number of network connections in CentOS

CentOS uses external access by default, and the total number of TCP links initiated is less than 28232. It can be calculated by the result of the following command $ cat /proc/sys/net/ipv4/ip_local_port_range What I get here is: 32768 60999 The subtraction of the two is equal to 28231, which means that the number of external TCP connections is 28231. There are several ways to increase the number of available TCP connections: 1....

programmer group

C practical exercise topic 21 - monkeys eat peaches

Title:Monkey eat peach problem: the first day the monkey picked a number of peaches, immediately ate half, not addicted, and ate one more 
 the next morning, he ate half of the remaining peaches, and another one. I ate half and one of the leftovers of the previous day every morning. When I wanted to eat again on the morning of the 10th day, there was only one peach left. How many were picked on the first day. Program analysis:Take...

fortune.com fortune.com

Shell announces big layoffs as the price of its net zero restructuring plan becomes clearer

Royal Dutch Shell, the Anglo-Dutch energy giant, said on Wednesday it would lay off up to 9,000 people, as the company faces economic headwinds from the COVID-19 pandemic and as it begins restructuring to hit its goal of net zero emissions by 2050. “We are doing this because we have to, because it is the right thing to do for the future of the company,” CEO Ben van Beurden said in an interview posted on the company’s website...

programmer group

C ා complete record of steps for simple operation of mongodb

preface Mongodb is a high-performance, open-source, modeless non relational database product written by C + +, which is the database with the most abundant functions and the most like relational database. It extends many functions of relational database, such as auxiliary index, range query, sorting, etc. Mongodb mainly solves the problem of access efficiency of massive data. After the rise of distributed data, mongodb uses more...