Database Administrator

1. Try not to use like '%' 2. For like '%' (not starting with %), Oracle can apply the index on colunm 3. For like '%... '(Not ending with %), you can change it to like' % 'in the form of reverse + function index' Create a test table and Index. Note

-- Oracle method 1SELECT * FROM(Select a. *, rownum rn from (SELECT * FROM ss_custinfo)Where rownum )Where rn> = 21; -- Oracle method 2SELECT * FROM(Select ss. *, rownum rn from ss_custinfo ss)WHERE rn = 21;  -- Oracle method 3SELECT *

1: Windows platform, because the Windows operating system uses the gb2312 character by default, while mysql uses latin1 for the client and server by default during installation, this leads to a mismatch between character set and character

SGA is the memory area used to store database information, which is shared by database processes. It contains data and control information of the Oracle server. It is allocated in the actual memory of the computer where the Oracle server resides. If

When I was working on a project today, a problem occurred while inserting data into the table. The database reported a violation of the unique constraint and the solution was simple: The project uses the Oracle database. In the early stage, I

In the following code, some struct types are unclear, such as THD, st_vio, and pollfd. However, we can see that MySQL uses the Select model to receive client connections. It is also found on the internet that unix_sock refers to the communication

SQL * PLUS allows you to create a login. SQL file. This script is executed every time SQL * PLUS is started. In addition, you can create an SQLPATH environment variable. In this way, no matter which directory the login. SQL script is located, SQL *

1. The steps for compiling an Oracle stored procedure are as follows: Create or replace procedure P_AUTO_CREATE_PARTITION (Result Out int, LogErrDesc Out varchar2 ) Is Type TypeTable is table of varchar2 (20 ); CreatePartitionErr exception;

In the morning, the Provincial Social Security Project Team responded that the database had a system-type SQL statement, which occupied a lot of resources and seriously affected the database performance. The specific SQL statement is: Select count (

[Oracle @ oracle_taowei_RedHat ~] $ Lsnrctl status check whether the listener is startedIf the listener is not started, run the command lsnrctl start to start the listener (lsnrctl stop to stop the listener)After the listener can be started with

The security management mechanism of Oracle10g listeners and oracle9i have been greatly changed. The Listener security mechanism uses the Password and Local OS Authentication methods. When Local OS Authentication is used, even if a listener password

View the time of the current database Select sysdate from dual To export data in expdp, you can specify flashback_time For example, HP-UNIX server export: Expdp test/test DIRECTORY = EXPDP_DIR dumpfile = hyomswas20151114.dmp logfile = hyomswas201

Write a test program when using C in Linux to operate MySQL database IntMain (Void) { MYSQL m_mysql; Mysql_init (& m_mysql ); Const CharPLocalhost [] ="Localhost"; Const CharPUser [] ="Root"; Const CharPPass [] ="123456";

First of all, the environment required for installation is not mentioned in Mysql and Python. MySQLdb is installed. Free in http://linux.bkjia.com/ The username and password are both www.bkjia.com The specific download directory

When using Oracle, there is a big difference from the previously used SQL server. in Oracle, users are a key and delicious thing. Oracle ranks the second largest among large databases. The largest database is db2 and the third database is sybase.

Flashback query traces the pre-image data stored in the rollback segment to obtain the data before the change. This allows you to quickly restore and roll back the data before the pre-image is overwritten. The flashback feature is affected by the

 1. Related Concepts The concept of Rowid: rowid is a pseudo column. Since it is a pseudo column, this column is not user-defined, but added by the system itself. Each table has a pseudo rowid column, but the table does not physically store the

A table is designed in PowerDesigner15, and you want to connect to Oracle through PowerDesigner, and then generate the table directly in the database. Set the connection options according to the methods provided on the Internet, and click the test

Redo is the information recorded in Oracle online (or archived) redo log files and used to redo transactions. undo is the information recorded in oracle's undo segment, used to cancel or roll back a transaction. The undo operations on the database

After Oracle is installed, the installation is successful, but errors occur when dbca and netca are running.[Oracle @ db1 ~] $ Netca Oracle Net Services Configuration:## An unexpected error has been detected by HotSpot Virtual Machine:## SIGSEGV