Oracle

Use hint to force a specified index when the Oracle Optimizer is unable to use a reasonable index.To continue the example of Oracle performance optimization operation VII, Oracle defaults to the fact that the values of the columns in the table are

Continue with the example of Oracle performance optimization Operation eightBecause there are queries involving disposalcourseflag=6 in the actual query, it would be very unwise and inefficient to use the index on that field at this point.So in this

Writing a function first is a way to MD5Create FUNCTION invarchar2)RETURNvarchar2isBEGIN RETURN = Upper (P_STR))); END;And then call inside the stored procedureCreate procedure as begin Update Set User_pwd=get_md5 ('123456'); End

Because of a monitoring configuration error# Listener.ora Network Configuration file:d:\oracle\product\10.2.0\db_1\network\admin\listener.ora# Generated by Oracle configuration Tools. Sid_list_listener = (sid_list = ( Sid_desc = (sid_name =

Transaction: A separate logical unit of work. It has a specific series of SQL statements that must be successful or failed as a whole. is an all-or-nothing, very personality of the East.Four properties of a transaction--acid properties: Atomicity

Using the table under the Scott user,1. Query All contentSELECT * from EMP;2. Query employee information, including employee number, name, position 3 informationSELECT empno,ename,job from EMP;3. Find All JobsSELECT JOB from EMP;4. Check all

Oracle creates self-growth write sequences and write triggers, not as convenient as MSSQLSERVER. But it is also a hassle, recorded as follows:In Oracle, you can create a separate sequence for the primary key of each table, and then get an

Slow query speed due to a large number of delete operations causing the space to not be released and the horizontal bit high--high level position due to a large number of delete operations causing the space to not be releasedALTER TABLE

[Email protected] ~]$ export ORACLE_SID=ORCL[Email protected] ~]$ Sqlplus/as SYSDBASql*plus:release 10.2.0.1.0-production on Mon Nov 10 23:04:36 2014Copyright (c) 1982, 2005, Oracle. All rights reserved.Connected to an idle instance.sql> startup

WHERE clauses with "in", "or" often use worksheets to invalidate indexes;If you do not produce a large number of duplicate values, you can consider taking the sentence apart; the split clause should contain an index.Cases:Select COUNT (*) from stuff

1, the table's primary key, the foreign key must have the index;2, the data volume of more than 300 of the table should be indexed;3. Tables that are often connected to other tables should be indexed on the connection field;4. Fields that often

Any action on a column can result in a full table scan, where the so-called operations include database functions, calculation expressions, and so on, to move the operation to the right of the equation whenever possible.Even remove the

Oracle performance optimization operation 1: Avoid Column Operations Any operation on a column may cause a full table scan. Here, the so-called operations include database functions, calculation expressions, and so on. During query, try to move the

Oracle user password Modification How to change the user password in Oracle In the Oracle database, use alter user to change the user password. Syntax Alter user user_name identified by new_password; Parameter description: User_name: the

Common oracle index creation rules 1. The table's primary key and foreign key must have an index; 2. Indexes should be available for tables with more than 300 of the data volume; 3. For tables that are often connected to other tables, indexes

Oracle password attempts Lab Environment   Operating System WIN7 64bit Database Oracle 11G R2 (11.2.0.1.0)   Premise: when a user attempts to log on with a wrong password, the user will be locked. Lab: When you use

Considerations for oracle Transaction Processing (notes) and oracle Transaction Processing Transaction: An Independent logical unit of work. It has a specific series of SQL statements that must be successful or failed as a whole. It is a kind of

Oracle performance optimization operation 2: Avoid unnecessary type conversion It should be noted that the potential data type conversion should be avoided as much as possible. For example, if you compare the numeric data with the numeric data,

Oracle index details (notes) 1. oracle index null When a single column index is created on an empty value column, if the search condition is null, it can be seen in the interpretation plan that oracle does not use index query for this

Oracle continuous data processing example The function described in the following section is to have a table in the Oracle database, which stores continuous time records and a tag bit. Now you need to obtain a result set: when the flag bit is 0, the