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; *

If this error occurs, the master database loses archive, and the slave database cannot synchronize logs. Media RecoveryWaiting for thread 1 sequence 70 Fetching gapsequence in thread 1, gap sequence 70-72 Completed: ALTERDATABASE RECOVER MANAGED

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

01. query all data in the employee table and describe the disadvantages of using * Select * from emp; 01. query the salaries of employees whose job is 'President' Select sal from emp where job = 'President '; 02. query the information of employees

I. What is a grouping function? The grouping function acts on a group of data and returns a value for a group of data. Ii. Grouping function types Avg, count, max, min, stddev (standard variance), sum. Function Name Function Description

Condition branch statement•IF statement:-IF-THEN-END IF-IF-THEN-ELSE-END IF-IF-THEN-ELSIF-END IF-Case statement:• Cyclic statements-LoopSyntax: IF condition THEN Statements; [ELSIF condition THEN statements;] [ELSE statements;] End if;

1. Introduction 1. Index: (1) A table-independent schema object that can be stored in a disk or tablespace different from the table (2) If an index is deleted or damaged, it does not affect the table. Only the query speed is affected. (3) once an

Steps for upgrading Oracle from 10 Gb to 11 GBDatabaseOld Version: 10.2.0.4New database version: 11.2.0.2OS: Solaris 10Reference: Complete Checklist for Manual Upgrades to 11gR2 [ID 837570.1]Part 1-install 11gR2 SoftwareHereSoftwareOfInstallFor more

Orabbix cannot obtain the solution for Oracle DB Size and DB Files Size These days, when studying Orabbix, I found that Zabbix could not obtain the Size of DB Size and DB Files. Later I found the problem lies in the configuration of

The Oracle paging query is generally implemented as follows:Select * from (Select a. *, rownum r from (Your own SQL) A where rownum ) Where r>? If this SQL statement is sorted by a field containing repeated values Duplicate records will be found on

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

Environment: PLSQL Developer 7.1.5 Oracle 11.2.0 Oracle does not specify an auto-increment column as MYSQL or MSSQLServer does. However, in Oracle, the SEQUENCE can be used to automatically increase fields. In Oracle, SEQUENCE is called a SEQUENCE.

Oracle user status Currently, databases, especially Oracle databases, are used in many industries. However, many enterprises seldom invest in database management and maintenance. The actual problems are self-evident: 1. DBAs have worked very hard to

If you have not installed or used sqlite, you can use SQLite3 for installation and basic operations. 1. Create a database test. db Cd ~ / Sqlite3 test. db In this way ~ /A database file test. db is generated under the directory. 2. Create a table

When the Oracle database is remotely restored, it takes a lot of space and a long time to completely restore the entire database.If the mode-based recovery method is used to recover only all objects in a certain mode, instead of all the data, this

[Root @ www.bkjia.com ~] # Yum-y install mysql-server[Root @ www.bkjia.com ~] #/Etc/rc. d/init. d/mysqld startInitializing MySQL database: Installing MySQL system tables...OKFilling help tables...OK To start mysqld at boot time you have to

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. view the default tablespace of the current user: SQL> select username, default_tablespace from user_users; 2. view the role of the current user: SQL> select * from user_role_privs; 3. view the current user's system permissions and table-level

The database initialization parameters used for Oracle Database startup are usually obtained using the show parameter command in sqlplus. However, only some public parameters and modified hidden parameters are shown here. Oracle also has a number of

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.