Oracle

We often say that the database instance, actually refers to the database memory structure and process structure. We install database software in large part by installing its memory and process component structure. In the previous section we

First, the constraint: Skip, MSSQL is not very usedSecond, view: This is still more useful, especially when working with other companies, often provide a view of each other1. Create VIEW: Created OR REPLACE view XX as SELECT * from XXX; Easy update

There was a problem writing the Oracle stored procedure a while ago.Originally written like thisIf 1=2 ThenNullElseIf 1=3 ThenNullEnd If;The ElseIf does not change color in the PL/SQL editing environment, stating that it is not a keyword.Later

One, the data blockThe unit in which Oracle manages storage space in a database data file is a block of data. A data block is the smallest (logical) unit of data in a database and is the smallest I/O unit. Corresponding to the data block, the

gets the execution plan6kind of Method1. explain plan for acquisition;2. set autotrace on ;3. Statistics_level=all;4. Direct Access via dbms_xplan.display_cursor input sql_id parameters5. 10046 trace trace6. Awrsqrpt.sqlApplicable occasions Analysis1

1. Standard SQL specificationOne, single IF1, if A= ... Then.........end if;2, if a= ... then......else....end if; two, more IfIf a=. Then......elsif a=. Then....end if; The middle here is "elsif", not else IF. Special attention is needed

--Creating a stored procedure for adding a local database Create or replaceprocedure Pro_electric_record as begin insert into Electric_meter_record (Id,basestati On_id,name,meter_number,createtime) Select Sys_guid (), substr (s.sname,0,36),

Login without password: sqlplus/as sysdbaView all current databases: select name from V$database;View current database connection User: Show userView all tables for the current user: Select table_name from All_tables;View table structure: DESC table

has been using MySQL, has recently switched to Oracle, Oracle's first step is the JDBC connectionThe first step: Download the jar package, I use the oracle11g is Oracle6.jarStep two: Load the jar packageThen find the downloaded Jar location.Step

stored procedures and stored functionsThat is stored in the database for all user programs to call.Sub-ProgramCalled stored procedures, stored functions.What are the differences between stored procedures and stored functions? Store function: You can

Database in the daily use of the process, continuous insert,delete,update operation, resulting in the table and index fragmentation is inevitable, fragmentation is more, SQL execution efficiency naturally poor, the reason is very simple, high

malloc implementation of the Lnux kernel (Oracle's cache buffer shadow)This article original for freas_1990, reprint please indicate source: http://blog.csdn.net/freas_1990/article/details/12845059This article introduces the principle of malloc, and

installation of Oracle database :One:Install the time can be set to unlock the user generally by default is to unlock SOCTT users and HR users;Oracle's Super User is SYSDBA This user can also set a password when installing, aYou can set the password

1.Create userSql>--For example, create a user named Xiaoming with a password of A123sql> Create user xiaomingidentified by A123;The user has created.Sql> Show UserUSER is "SYS"2.granting permissions to usersSql>--grant permissions to User

The contents of this chapter include: Processes and stores a specific date and time. The date type can store century, 4-bit years, months, days, hours, minutes, and seconds With timestamp timestamp, the timestamp can store a specific

12. Check the average score of the course with at least 5 students enrolled in the score table and begin with 3.Select cno,Count(CNO),avgfromgroup by has Count(CNO)>=5 and substr (CNO,0,1)=' 3'13, the query score is greater than 70, less than 90 of

1,oracle View:User view, which has been user_ as a prefix, and records information about the users ' objects;The all view, prefixed with All_, records the user object information and the object information that is authorized to access it.DBA view,

additionSelect Sysdate,add_months (sysdate,12) from dual; --plus 1 yearsSelect Sysdate,add_months (sysdate,1) from dual; --Add JanuarySelect Sysdate,to_char (sysdate+7, ' Yyyy-mm-dd HH24:MI:SS ') from dual; --plus 1 weeksSelect Sysdate,to_char

Oracle columns of multiple rows of data are spelled into a single line of characters oracle provides two functions Wmsys.wm_concat and Listagg functions.    www.2cto.com   First Introduction: wmsys.wm_concat Example:        ID  name        1   aa    

Sequence Creation Method:CREATE SEQUENCE [schema.] Sequence[INCREMENT by integer][START with integer][MAXVALUE Integer | Nomaxvalue][MINVALUE Integer | Nominvalue][CYCLE | Nocycle][CACHE Integer | NOCACHE][ORDER | Noorder]There are three scenarios