Database Administrator

Create table test as select * from dba_objects where rownum BeginFor I in 1 .. 7 loopInsert into test select * from test;Commit;End loop;End;BYS @ bys001> select count (*) from test;COUNT (*)----------1280000Elapsed: 00:00:01. 12BYS @ bys001> select

Query the character set of the current databaseBYS @ bys1> select userenv ('language ') from dual;USERENV ('language ')----------------------------------------------------AMERICAN_AMERICA.AL32UTF8BYS @ bys1> select * from

DECLARE @ OldId varchar (50) DECLARE @ CustomerID varchar (50) DECLARE My_Cursor CURSOR -- Define the cursor for (select CustomerID, oldid from Customer where Area = 'bj ') -- locate the desired set and put it in the cursor OPEN My_Cursor; -- OPEN

1. Explain the differences between cold backup and hot backup and their respective advantagesAnswer: Hot Backup is applicable to databases in the archive mode. When the database is still in the working state, it is backed up. Cold backup refers to

When xmanager is used for oracle installation in a linux Chinese operating system, garbled interface may appear. You can solve this problem by using the following methods: 1. Modify the environment attribute vi/etc/sysconfig/i18n LANG = "en_US.UTF-8

-- Use the regular expression with t as (select 'guangdong, Guangxi, Hainan, Guizhou, Yunnan 'str from dual) SELECT REGEXP_SUBSTR (str,' [^,] + ', 1, ROWNUM) province FROM tCONNECT by rownum PROVINCE ------------------------------ Guangdong,

With the data pump expdp, impdp can import and export data on the server, with high efficiency.You do not need to set the environment variable NLS_LANG. By default, it will go to the character set of the database. Create directory backup as '/backup

/* Implemented functions: Use a database to store text data and read it and put it in the current project for analysis: the difficulty is not great. The key is to master the file stream, and there are not many database operations, but the file

1. Non-connection mode (dependent on datasets)2. Connection Mode (directly operate on the database) You can use a command object to execute SQL statements or stored procedures. If the execution result returns a record set, you can use the

It is very convenient for CHAR to store fixed-length data, and the indexing efficiency of CHAR fields is high. For example, if char (10) is defined, no matter whether the data you store reaches 10 characters, it takes up to 10 characters. To store

Common methods to solve IO problems: Through SQL optimization, you can reduce the IO requests of the database: Adjust the instance parameters to reduce the database's IO requests: Compared to 1000 data transmission requests

Aggregate functions for computing in SQL statements: COUNT (*): calculates the number of tuples. COUNT ( SUM/AVG/MAX/MIN (): Calculate the SUM, average, maximum, and minimum values of a column (numeric type) Let's analyze the types of

After the database is upgraded, how can I determine whether the upgrade is successful? Function rounding? Returns a value rounded to the specified number of decimal places.Number: value to be processedThe number of decimal places is set to select

C processing ing Large Memory Optimization This appendix provides information for Processing memory optimization with large page tables on the Linux operating system, using Hugepages. It contains the following topics: Overview of HugePages

I 've been so busy recently that I haven't written a blog for three months. This requirement was met in the use of Mongo, but I think it is easier to put this requirement into traditional RDBMS. The requirement is as follows: assume that your

The storage engine layer can decide how to lock data by accepting the lock type passed by the Server layer.Table locks are implemented at the Server layer. If MyISAM is not implemented by itself, the table locks passed at the Server layer are used

Database movement is also a common phenomenon. After all, there are various reasons to force us to move. So how can we move faster? See the following. When using an Oracle database, data in the database is often moved from one database to another.

To reduce IT complexity and improve data quality, enterprises always want to integrate their businesses to fewer database platforms. However, experts believe that before the database standardization project, pay attention to cultural and technical

Editor's note: many friends may not know where to start when getting started with MySQL's dual-machine synchronization requirements. In fact, this is one of the functions supported by MySQL itself. This article provides a preliminary idea about

The first concern of people who use database replication is the performance consumption of the master server and backup server. I am also very worried about this. After checking for half a day, I basically did not find similar test instructions, I