Category:DBT

  • Database exercise (student table)

    Time:2019-12-9

    Create table 1. Create student table, score table and course table create  table student(  sid     int(11) primary key not null,  sname   char(25) not null,  age     int(11) not null,  sex     char(2) not null,  department char(40) ,  address  char(200) ,  birthplace  varchar(256) ); create  table sc(   sid   int(11) not null,   cid   int(11) not null,   […]

  • Oracle about basic operation of log file

    Time:2019-12-9

    1. Query which set of log files the system uses:SELECT * FROM V$LOG; 2. Query the log file corresponding to the group being used:SELECT * FROM V$LOGFILE; 3. Force log switching:ALTER SYSTEM SWITCH LOGFILE; 4. Query history log:SELECT * FROM V$LOG_HISTORY; 5. Archive Mode of query log:SELECT DBID,NAME,CREATED,LOG_MODE FROM V$DATABASE; 6. Query the information of […]

  • SQL Server’s statement category database normal form system database composition

    Time:2019-12-9

    Preface Finally, on this day, I will start to learn the database system again. If there is no accident about the database, I will update one article regularly every day, and the content will not contain too much, short content and in-depth understanding. SQL statement category SQL statements include the following three categories (1)Data definition […]

  • MySQL: data integrity

    Time:2019-12-9

    Data integrity includes entity integrity, domain integrity and reference integrity. Reference integrity: Referential integrity refers to the design of multiple tables, mainly using foreign key constraints.Multi table design: one to many, many to many, one to one design I. entity (line) integrity Entity integrity is achieved by the primary key of the table.Use the primary […]

  • Installation and use of mongodb in Windows

    Time:2019-12-9

    First, install mongodb 1. Download address: http://www.mongodb.org/downloads 2. Extract it to the directory you want to install, such as D: \ mongodb 3. Create folders D: \ mongodb \ data \ dB and D: \ mongodb \ data \ log, which are used to install dB and log files respectively. Create a log file mongodb.log […]

  • Three paging methods of using rownum in Oracle

    Time:2019-12-9

    Rownum is a unique keyword in Oracle database. It returns a number representing the row number of the record. Basic knowledge: rownum can only query < or < = conditions. If rownum needs to judge the range from 51 to 100, it needs to first find out the rownum of each row, and then use […]

  • Redis compares memcached with CentOS for installation and configuration details

    Time:2019-12-9

    Redis is an open-source, network supported, memory based, key value pair key value database. This article mainly introduces redis‘s comparison with memcached and detailed installation and configuration under CentOS. You can learn more about it if you are interested. Get to know redis Redis is an open-source, network supported, memory based, key value pair key […]

  • SQL2005 learning notes window function (over)

    Time:2019-12-9

    1. introduction: The window functions in SQL Server 2005 help you quickly view different levels of aggregation, which makes it easy to aggregate totals, move averages, and perform other calculations.Window functions are very powerful and easy to use. You can use this technique to get a lot of statistics immediately.A window is a set of […]

  • MySQL LAN remote connection settings – Windows

    Time:2019-12-8

    In my work, I met that MySQL database is stored on my computer, and other computers need to read and write data together (similar to redis concurrency), so my computer must open MySQL remote connection. I. authorization 1. Connect to database   mysql -uroot -p    2. Select system library, MySQL   use mysql; Of course, you […]

  • More than 120 seconds?

    Time:2019-12-8

    //2019/7/31 18:41:14I think it’s over. Is it hot to strike? But it’s been almost 30 hoursInadvertently checktail -500f /var/log/messagesIt is found that there are some “more than 120 seconds” and “more than 120 seconds” in the kernel… Analysis before workAt first glance, the analysis of two posts is very reasonable. Let’s do it. Bold is […]

  • Explain SQL Server database architecture and objects, define data integrity

    Time:2019-12-8

    Preface In this section, we will continue our journey of SQL. In this section, we will talk about some basic knowledge and what we need to pay attention to. If there is something wrong, please point out the short content and in-depth understanding. Database schema and objects The database contains the schema, and the schema […]

  • A tutorial of installing MySQL under CentOS 7

    Time:2019-12-8

    Recently, I plan to deploy the cloud disk on my home server, so I started a series of environment building operations. When installing mysql, I found that it was different from the previous one, so I recorded it to avoid the next search problem like today. I. uninstall the old version Use the following command […]