Database Administrator

Select count (1) from table use index (unique key ); Faster than using primary key indexes. I tested million production environment data, at least faster3Times .....   EXPLAINSELECT COUNT(1)From'Order'UseINDEX(PRIMARY) \ G; *

The role, benefits, and disadvantages of ASM storage are not described here. There are many documents related to google! This article mainly records how to use the ASM storage in Oracle 11.2.0.3! Related software packages can be found

Recently, many features have been developed, and I feel quite familiar with the English name for many programming processes. However, to view the functions, I need to open comments or code at each point. I feel very depressed. We can see packages

I. Transaction Concept Concept: transactions in databases are logical units of work. A transaction is composed of one or more SQL statements that complete a group of related behaviors, the transaction mechanism is used to ensure that the operations

When I first came into contact with PHP and started to contact MYSQL, many people said: "MySQL is enough to run on a small site with hundreds of thousands of IP addresses a day. If it is a few millions of IP addresses, it won't work ", I don't

For work, you need to write a method or SQL statement to retain the decimal point. For decimal places of the number type, if it is 0.5 or-0.5, it will be displayed during printing. 5 or -. 5. Obviously it's not what I want. I wrote a simple one

1. user_source Process Code of the current user2. user_objects contains all database objects owned by the user3. user_segments4. user_tables tablespace and tablespace Information5. user_tab_partitions partition information6. user_views7.

Recently, I have been playing with DG. Due to the shortage of disk resources, a policy for archiving logs is required. I found several scripts on the Internet and found that writing is so troublesome. Mao, So I simply wrote one, and the actual path

Problems with Oracle DG archive setup Verification -- Master database SQL> col statusForA10 SQL> col destinationForA20 SQL> col errorForA20 SQL>SELECTSTATUS, DESTINATION, ERRORFROMV $ ARCHIVE_DEST; STATUS DESTINATION ERROR -----------------

I. Performance adjustment objectives of Rodo Log: Among the many factors that can affect Oracle performance, Redo Log-related factors are, to some extent, the most important and most noteworthy. In an OLTP system, Oracle tries its best to complete

I used Ubuntu 10.04 LTS Server. The HDD was faulty a few days ago and the system was pregnant. I had to wait for an 80 GB HDD to be eliminated with IT. How can the company be so poor, I still use my computer as the server 7 or 8 years ago. Is IT

1. Create a table: Create table test (id int, name varchar (20), quarter int, profile int )) Insert into test values (1, 'A', 1,1000 );Insert into test values (1, 'A', 2,1000 );Insert into test values (1, 'A', 3,1000 );Insert into test values (1, 'A'

Statement for inserting database data:Insert into testtab (FIELD1) VALUES ('test ')If the string to be inserted to the database contains single quotation marks, escape is required. For example, to insert "It's a tree.", the SQL statement is as

Function: The purpose of using a function is to operate data. Process the input variable and return a result. There can be many variables. The input variables can be column values or expressions. Functions can be nested. The result of the inner

State online can be started only after the dual-node RAC is successfully installed on the VM. you can always have several UNKNOWN machines after each restart, if you can start them manually. crs_start ora. xxxxx, or crs_start-f xxxxx If no error is

Before executing an SQL statement, Oracle needs to first check the SQL Execution Plan and then execute the SQL statement according to the execution plan. The optimizer is responsible for analyzing the execution plan, under different conditions, an

1. Command installation: yum install mysql-server 2. built-in startup: CentOS6.2 comes with mysql5.1 installed, and the root identity (mysql-u root-p) has no password; System-> Management-> service, select mysqld, and set auto start and start the

MHA is divided into management nodes and database nodes. database nodes are composed of mysql master-slave or master-slave nodes. When the master database fails, the management node will automatically upgrade from the master node to the master node;

Differences between Oracle row triggering and statement triggering 1. the row trigger has a for each row clause. The statement trigger does not have a for each row clause.2. the row trigger can have the when as the trigger limit. You can use new/old.

In the basic configuration information table of the application, some dictionary information is saved. The key value is added by the application in sequence as needed. This type of requirement is used for primary key field value management. The