Database Administrator

Each table in Oracle has a rowid, which is an 18-character string, for example, AAANgBAABAAAO/KAAA. it contains a string consisting of A-Z, a-z, 0-9, +. yes. Where the A-Z corresponds to 0-25, a-z corresponds to 26-51,0-9 corresponds to 52-61, +

1. Preparations1.1 If the server version is used, a graphical interface must be installed.$ Sudo apt-get install Ubuntu-desktop1.2 install necessary library packages$ Sudo apt-get install build-essential libaio1 gawk ksh libmotif3 alien libtool

1. ConceptsHadoop is an Apache open-source distributed computing framework, which includes DFS and MapReduce, a distributed file system. MongoDB is a document-Oriented Distributed Database and NoSql, here we will introduce a MongoDB Hadoop driver.

The following uses PostgreSQL 9.1.2 as an example. You can also refer to the INSTALL file in the package. The procedure is as follows: 1. Download the PostgreSQL source code package, put it in any directory http://www.postgresql.org/ftp/source/v9.1.2

Fault symptom: 1. log errors of the master database Sun Nov 27 12:31:34 2011 ErrorsInFile/home/Oracle/admin/zjtv/bdump/zjtv1_arc0_803242.trc: ORA-16055: FAL request rejected ARCH: FAL archive failed. Archiver continuing Sun Nov 27 12:31:34 2011

1. Encryption Algorithm create or replace function encrypt (in_string varchar2, shift number) return varchar2 isLv_out_string varchar2 (100 );Lv_in_string varchar2 (100 );Lv_length number (5 );Lv_count number (5 );Lv_temp varchar2 (1 );Lv_shift

In MongoDB1.6, it is easy to add members to the Replica Set as follows: # Add new membersRs. add ("192.168.95.210: 10000 ");# Add new elected membersRs. addArb ("192.168.95.216: 10001 "); With this configuration, Mongo automatically synchronizes

1. Switch to the database user on the console: su-OracleIi. Input: lsnrctl start; start the listener;3. Start the database;4. operate databases, such as creating users, granting permissions, and creating tables;5. Shut down the database;6. Disable

1. Create an Oracle database (if any ).2. Create an OEM user and create a directoryMkidr-p/oracle/oem_12cChmod-R oem: oisntall/oracle/oem_12c3. modify Database ParametersSu-oracleSqlplus/AS SYSDBAAlter system set processses = 300 SCOPE =

I encountered some trouble. Although it was not solved, it was a reminder. Today, the username created with Grant is "DanielW", and the logon password is incorrect. Create a new one. The username is "Daniel @ localhost", that is, add the host name,

Oracle Database cursor and stored procedure Spool abc. log -- start logging Create or replace procedure db. PROC_FIRST (flag out interger,T_DATE IN VARCHAR2) AS Varno varchar2 (20 );Varprice varchar2 (20 ); CURSOR mycur (vartype number) isSelect emp_

This time, we will separately investigate the time of Master/Slave latency. The master-slave latency mentioned here does not refer to the "Slave database update performance cannot keep up with the master database", but to the "Delay Time for a

OracleAs a well-known database product in the industry, it has been widely used in enterprises. The first step to use the software is to successfully install the software. In this exampleOracleInLinuxThe installed version isOracle 10g.

Recently, I found several random SQL queries in mysql on the Internet. I recorded the results.SELECT * FROM uchome_mtag AS a JOIN (select max (tagid) AS id FROM uchome_mtag) AS BON (a. tagid> = FLOOR (B. id * RAND () LIMIT 50I found a problem after

1. After signing your process, temporarily declare authorization: authid current_user. The Code is as follows: Create or replace procedure proc_test_name authid current_user As Begin Execute immediate 'create database link dblink_name connect

Create a table Spam Take a look at the data file to be inserted MysqlYesExecutable filesMysqlimport,There is anotherMysqlInLoad data,ThisTwoCommand to import formatted data to the database from a file. If a file contains a large amount of data,

Conversion between different data typesIn the value assignment statement, the data type is implicitly converted, and the implicit conversion should be avoided as much as possible, because the written SQL statements are hard to understand and are

SQL syntax writing is very long, and SQLPLUS is not automatically completed. If you forget the format, you can get help through the document. SQL syntax description in the official document:1. keywords and Parameters Square is the key word. elliptic

Recently, I participated in a company project and planned to quickly respond to large-scale queries on the online platform. The estimated total data volume is about 2-3 billion records, the database concurrency is about 1500 per second, and the

The amount of data in a table in the database is large at work, which is a log table. Under normal circumstances, there will be no query operation, but if there is not much data in the table sharding, it takes several minutes to execute a simple SQL