Database Administrator

The concept Data Model (Conceptual Data Model) is also known as the information Model. It is based on the object-link theory and expanded. It models the information Data from the user's perspective, it is mainly used for Conceptual Design of

Select trunc (SYSDATE-1, 'Year')-1, 'Year') from dual -- Get first day of last YEAR, sysdate-1 indicate current day in DW case. Select add_months (trunc (sysdate, 'Year'), 12)-(1/86400) from dual -- get the last minute and second of the year. Select

Most of the time, the operating system is Windows, and Liunx is rarely understood.During this time, an image system requires that all applications be deployed on the RedHat system. In this way, there are two software usage problems: 1. Database 2.

Oralce: [Function description]: the current system time is automatically inserted into the getSysDate table every minute. [1. Create a test table] Create table getSysDate (test date ); [2. Create a stored procedure for scheduled execution] Create or

I. date type usage The date type subtraction only obtains the number of days.SQL> SELECT sysdate-(sysdate-1) FROM dual;SYSDATE-(SYSDATE-1)-------------------1Make an experiment:Create table t2 (d1 date, d2 date); -- create a tableInsert into T2

1. What is bitmap index? You only need to store the key value in the index segment, instead of rowid. Each bit in a bitmap index is equivalent to a row that may have this key. 2. Benefits of creating a bitmap Index I. It can save storage index space.

If you are familiar with Oracle databases, I think you will not be familiar with Thomas Kyte. The asktom.oracle.com website hosted by Tomas has been well-known in the Oracle field for decades and is far from Lucky. Recently, in the library, I

Affected MySQL 5.0 versions earlier than 5.0.70; MySQL 5.1 versions earlier than 5.1.28 /* Create table */create table 'certuserid' ('certuserid' int (11) not null auto_increment, 'userid' int (11) not null, 'certificateid' int (11) not null,

Compiling invalid objects is one of the common tasks of DBAs and database developers. The following two methods are provided to capture errors during compilation. I. Current Database Version Information and invalid objects 1. view the current

Logon username for Linux: Oracle Sqlplus/as sysdba Alter system set OS _authent_prefix = ''scope = spfile; Startup force; Create user oracle identified externally; Grant connect to oracle; Exit the current session and then su to oracle Exit

When creating a user,There is a default tablespace Parameter.You can view the viewDatabase_propertiesYou can see the corresponding information. SQL> select a. property_name, a. property_value from database_properties a where a. property_name like '%

When viewing the SQL Execution Plan, we will find that there are many table connection methods. This article introduces the table connection methods to better understand the execution plan and understand the SQL Execution principles. I. Connection

Recently, there are a bunch of Delete statements to be executed. The 34 Delete statements are written as one PROCEDURE for execution, but the execution plan and time of a single DELETE statement cannot be seen during execution, think of using

SKIP OptionExcludes datafiles or archived redo logs from the backup set according to the criteria specified by the following keywords.Note: You can also specify this option in the backupSpec clause. OFFLINESpecifies that offline datafiles shocould

When using spfile, you can use the v $ parameter. ISSYS_MODIFIABLE field to determine the initialization parameters that can take effect without restarting. V $ parameter. ISSYS_MODIFIABLE parameter Indicates whether the parameter can be changed

One day I met a colleague who asked me to help optimize an SQL statement, which took a long time to run. As a result, I queried the execution plan and found that the SQL was to perform a full table scan. At that time, I checked the definition of the

In Oracle databases, users and roles are closely related to database permissions. Correct understanding of user and role management is very important for database installation, this article mainly summarizes the user and role management operations

1. Create a tablespace1. Create a common tablespace to specify the initial size, which is automatically expanded. Maximum Size:(The maximum size of a single smallfile data file allowed by Oracle is 4194302 * blocksize, and the maximum size of a

This is an example of Tom's in-depth database architecture. Back up a table to an external file Create table gftuserOrganization external(Type Oracle_datapumpDefault directory tmpLocation ('test0801. dmp '))AsSelect * from all_objects From

Parameter changes:Skip-locking is not recognized in 5.5 and changed to skip-external-locking.Basedir =/usr/local/mysql5.5Datadir =/usr/local/mysql5.5/dataInnodb_data_home_dir =/usr/local/mysql5.5/dataInnodb_log_group_home_dir