Oracle

for each row returned by the query, use the rownum pseudo-column to return a number indicating the order in which Oracle selects rows from a table or joins rows.The first line of the selection is rownum 1, second behavior 2, and so on.You can use

Oracle Performance Optimization Operation V: Remove "<>" as much as possibleRemove the "<>" as much as possible, avoid full-table scans, and modify the "OR" if the data is an enumeration value with a fixed range of values.Cases:update serviceinfo

Indexes can still be used to improve efficiency when the selectivity of the index is low, but the value distribution of the data varies widely.A, the data distribution is not uniform in the special case, the selective index is also to be created.The

Oracle does not lock data if only select is used in Oracle. When the data is being modified by another process, the results obtained by using Select are not up to date.This requires a for update, and when Oracle finds that a record that satisfies

Original: Oracle Foundation shutdown and startupOne, shutdown command:Shutdown has four parameters: NORMAL, transactional, IMMEDIATE, ABORT. The default is normal if no parameters are taken.SHUTDOWN NORMAL: Do not allow new connections, wait for the

Oracle study--ipcs Manage shared memoryU shared memory, semaphore, queue information management under Nix/linuxUnder Unix/linux, there are often problems caused by shared memory, semaphores, queues, and other shared information that are not cleaned

problem : Update cannot be updated Table table 19 record, in when updated occasionally update occasionally update no move Update Action Execution the time , it's not moving. , It's like. is dead off the same .about the database

The previous action on any column may result in a full table scan, for example:select * from EMP where substr (ename,1,2) = ' SM ';But this kind of query is often used, and we can create a function-based index with the SUBSTR function.create index

Oracle's job, in fact, is a database built-in timing task, similar to the timer function in the code. The following are the use procedures:Here we simulate a scenario where the stored procedure is called periodically p_test_job insert data into

Dynamic SQL returns cursors:Create or Replace procedure Proc_validityduequery (P_regioncode in number, p_pscode in number, p_o Utputcode in number, p_pollutanttype in number, P_psclasscode in Varchar2, P_attencode in Varchar2, P_checkstatus

Increase the scope of the query to avoid a full range of searches.Example: The following query table record in time Actiontime less than March 1, 2001 of data:SELECT * FROM record where Actiontime The query plan indicates that the above query has a

First, what is the waterline (high water Mark)?All Oracle segments (segments, where, for ease of understanding, suggest segment as a synonym for a table) have a limit on the amount of data that can be accommodated in a paragraph, we call this cap

Oracle MinuskeywordMinuskeyword in SQLThere is a minuskeyword in SQL that uses two SQL statements to find out the results of the first SQL statement, and then see if the results are in the results of the second SQL statement. If there is, then this

(1) Oracle uses keep analysis function to take the most value record--the name of the employee with the largest wage Sal and its salary, and the name of the employee with the lowestSelectDeptno, Empno, ename, Sal ,Max(ename) Keep (Dense_rank

--Create a temporary table spaceCreate temporary tablespace test_temp tempfile ' d:/test_temp01.dbf ' size 30m autoextend on next 30m maxsize 2000m extent M Anagement Local;--Create TABLE spaceCreate tablespace test_data datafile '

Numeric function (learning notes), numeric function learning notes -- ************************************ Digital functions-- ABS: returns the absolute value. SELECT ABS(3),ABS(-100) FROM dual; Result: 3,100-- CEIL rounded up SELECT

Oracle performance optimization operation 8: Use HINT to forcibly specify an index When the ORACLE optimizer cannot use a reasonable index, the HINT is used to forcibly specify the index. In the example of "oracle Performance Optimization

PL/SQL basics 1 (notes), plsql -- Basic StructureDECLARE-- Variable Declaration: Declares the variables, types, cursors, and local stored procedures and functions used by PL/SQL.BEGIN-- Execution part: process and SQL statement, that is, the main

Mongodb installation and VerificationInstallation plan:System Environment: Centos-6.5Software: mongodb-linux-x86_64-2.6.5.tgz: Http://www.mongodb.org/downloadsInstallation machine: 10.10.10.110Upload location:/dataSoftware installation

Oracle arithmetic operations In Oracle's default installation, a SCOTT user has been created. The default password is tiger, which has four tables:Employee table (EMP), department table (DEPT), salary Registration Form and bonus table. Next, many