Database Administrator

Usage of order 1. Processing of null in order Default processing: Oracle considers null as the maximum value in order by, so if it is asc, it is placed at the end, and desc is placed at the top. We can use nulls first or nulls last to control the

ORA-27300 troubleshooting instance Recently, a customer reported that some pages of its core business system were running slowly, and the production database (dual-node RAC environment) encountered exceptions. After logging on to the BOSS database

Semi-synchronous replication instance of MySQL5.6 one master and multiple slaves Semi-sync introduction:By default, MySQL replication is asynchronous, which means that the master server and its slave server are independent. Asynchronous replication

Simple cold backup synchronization for Oracle databases in Linux and other Windows systems We have a financial system that focuses on the security of financial data. At the same time, we have two systems: a production environment (Linux) and an

Mongodb command guide and mongodb Guide Welcome to reprint, reprint please indicate the original address: http://blog.csdn.net/majianfei1023/article/details/45166827 1. What is MongoDB? In short, MongoDB is a type of database, such as mysql, SQL

Select into and insert into select, selectintoinsert I. Differences: Insert into select: used to copy the select result set to a new table. It is a standard SQL statement. Select into: Save the result to a variable. It is a plsql value assignment

Mysql for Mac and mysql for Mac 1. Install mysql 2. Start the mysql service in preference settings 3. Open the terminal and enter mysql. chenhong:~ chenhong$ mysql-bash: mysql: command not found 4. Set the mysql command and enter 1) alias mysql =

Mysql learning-InnoDB and Myisam, mysqlinnodbmyisam MysqlInnoDB and Myisam are two types of storage. When creating a table in Mysql, you can specify the options, as shown in: The following describes the differences between the two types of storage:1

SQL tutorials and SQL tutorials 1. SQL tutorial 01 -- install SQLite3 in linux 2. SQL tutorial 02--basic SQL statements 3. SQL tutorial 03--standard SQL data type 4. SQL tutorial 04 -- alter: add, modify, or delete columns in an

MySQL database trigger 1. Trigger with only one row of statements executed Trigger triggers are events that trigger certain operations, such as insert, delete, and update. For example: Create trigger t_user_trig before insertOn t_user for each

Report diversity data sources-MongoDB and report diversity-mongodb MongoDB and other nosql databases have advantages such as scalability and high performance, but their computing capabilities are weaker than traditional SQL databases. For example,

Python accesses the MySQL database and supports addition, deletion, modification, and query.Overview: I want to know more about database access operations. However, since I recently learned Python, I will use Python to implement it below. These

[They all say that select * is not good, ...], Select .. If you ask any experienced Database staff, they will tell you that SELECT * FROM... is not a good idea, so it is best not to use it. Today, I spent several hours testing some places

MysqlWorkBench, table creation --- shinepans, and mysqlworkbench1. Download workbench first: Http://url.cn/cVLpZ0 2. After the installation is complete, open and you will see an enabled mysql service. connect to it: 3. check your scheme:

DS sequence stack and Chain team to realize retrieval judgment and ds sequence Retrieval The basic operations of the sequence stack and the chain team will not be listed one by one. To realize the retrieval judgment, first understand what is the

Database learning, database Large-scale concurrency Optimize server configurations Use Server Load balancer Database Structure Design Middleware Optimization Data Cache Usage High database concurrency Database

(12) mysql cursor, 12mysql cursor Overview The query statement may query multiple records and use the cursor in the stored procedure and function to read records in the query result set one by one. In some books, the cursor is called a cursor. The

HBase createTable server-side source code analysis, hbasecreatetable All HBase request calls are implemented through the RPC mechanism. After the RPCServer listens to the request, it will parse the request content and then call the actual method

[LeetCode] DeleteDuplicateEmails, solution report, leetcode Question SQL query to delete all duplicate email entries in a table named Person, keeping only unique emails based on its smallest Id. Id Email 1

SQL: group data in Chapter 10. SQL: Required10.1 Data grouping Groups allow data to be divided into multiple logical groups so that each group can be clustered and computed.10.2 create a group SELECT vend_id,COUNT(*) AS num_prodsFROM ProductsGROUP