javascript barcode scanner OCA/OCP Oracle Database 11g All-in-One Exam Guide in Software

Generating Code-39 in Software OCA/OCP Oracle Database 11g All-in-One Exam Guide

OCA/OCP Oracle Database 11g All-in-One Exam Guide
Code 39 Extended Reader In None
Using Barcode Control SDK for Software Control to generate, create, read, scan barcode image in Software applications.
Create Code 3/9 In None
Using Barcode maker for Software Control to generate, create Code-39 image in Software applications.
In general, bitmap indexes should be used if The cardinality (the number of distinct values) in the column is low, and The number of rows in the table is high, and The column is used in Boolean algebra operations TIP If you knew in advance what the queries would be, then you could build B*Tree indexes that would work, such as a composite index on SHOP and CHANNEL But usually you don t know, which is where the dynamic merging of bitmaps gives great flexibility
Recognizing Code 39 Extended In None
Using Barcode scanner for Software Control to read, scan read, scan image in Software applications.
Code 3/9 Drawer In C#.NET
Using Barcode creation for VS .NET Control to generate, create Code 39 image in VS .NET applications.
Index Type Options
Painting ANSI/AIM Code 39 In .NET
Using Barcode maker for ASP.NET Control to generate, create USS Code 39 image in ASP.NET applications.
ANSI/AIM Code 39 Drawer In VS .NET
Using Barcode creation for .NET framework Control to generate, create Code 3 of 9 image in .NET framework applications.
There are six commonly used options that can be applied when creating indexes: Unique or nonunique Reverse key Compressed Composite Function based Ascending or descending All these six variations apply to B*Tree indexes, but only the last three can be applied to bitmap indexes A unique index will not permit duplicate values Nonunique is the default The unique attribute of the index operates independently of a unique or primary key constraint: the presence of a unique index will not permit insertion of a duplicate value even if there is no such constraint defined A unique or primary key constraint can use a nonunique index; it will just happen to have no duplicate values This is in fact a requirement for a constraint that is deferrable, as there may be a period (before transactions are committed) when duplicate values do exist Constraints are discussed in the next section A reverse key index is built on a version of the key column with its bytes reversed: rather than indexing John , it will index nhoJ When a SELECT is done, Oracle will automatically reverse the value of the search string This is a powerful technique for avoiding contention in multiuser systems For instance, if many users are concurrently inserting rows with primary keys based on a sequentially increasing number, all their index inserts will concentrate on the high end of the index By reversing the keys, the consecutive index key inserts will tend to be spread over the whole range of the index Even though John and Jules are close together, nhoJ and seluJ will be quite widely separated A compressed index stores repeated key values only once The default is not to compress, meaning that if a key value is not unique, it will be stored once for each occurrence, each having a single rowid pointer A compressed index will store the key once, followed by a string of all the matching rowids
Creating Code 3/9 In VB.NET
Using Barcode creation for .NET Control to generate, create Code 39 image in .NET applications.
Barcode Generation In None
Using Barcode printer for Software Control to generate, create bar code image in Software applications.
7: DDL and Schema Objects
Painting EAN-13 Supplement 5 In None
Using Barcode generator for Software Control to generate, create EAN-13 image in Software applications.
Creating UPC-A In None
Using Barcode creator for Software Control to generate, create GS1 - 12 image in Software applications.
A composite index is built on the concatenation of two or more columns There are no restrictions on mixing datatypes If a search string does not include all the columns, the index can still be used but if it does not include the leftmost column, Oracle will have to use a skip-scanning method that is much less efficient than if the leftmost column is included A function-based index is built on the result of a function applied to one or more columns, such as upper(last_name) or to_char(startdate, 'ccyy-mm-dd') A query will have to apply the same function to the search string, or Oracle may not be able to use the index By default, an index is ascending, meaning that the keys are sorted in order of lowest value to highest A descending index reverses this In fact, the difference is often not important: the entries in an index are stored as a doubly linked list, so it is possible to navigate up or down with equal celerity, but this will affect the order in which rows are returned if they are retrieved with an index full scan
Code-128 Generator In None
Using Barcode creation for Software Control to generate, create ANSI/AIM Code 128 image in Software applications.
Data Matrix Encoder In None
Using Barcode drawer for Software Control to generate, create Data Matrix ECC200 image in Software applications.
PART II
Print MSI Plessey In None
Using Barcode generation for Software Control to generate, create MSI Plessey image in Software applications.
Painting Bar Code In None
Using Barcode encoder for Font Control to generate, create bar code image in Font applications.
Creating and Using Indexes
Bar Code Drawer In None
Using Barcode maker for Microsoft Word Control to generate, create bar code image in Office Word applications.
Make EAN 13 In None
Using Barcode generation for Word Control to generate, create EAN13 image in Microsoft Word applications.
Indexes are created implicitly when primary key and unique constraints are defined, if an index on the relevant column(s) does not already exist The basic syntax for creating an index explicitly is
Paint Code 3/9 In None
Using Barcode creation for Font Control to generate, create USS Code 39 image in Font applications.
Create UPC-A Supplement 2 In .NET Framework
Using Barcode creator for ASP.NET Control to generate, create UPC Symbol image in ASP.NET applications.
CREATE [UNIQUE | BITMAP] INDEX [ schema]indexname ON [schema]tablename (column [, column] ) ;
Generating GS1 128 In Visual Basic .NET
Using Barcode maker for Visual Studio .NET Control to generate, create GTIN - 128 image in .NET applications.
2D Barcode Drawer In Visual C#.NET
Using Barcode generator for .NET Control to generate, create Matrix Barcode image in .NET applications.
The default type of index is a nonunique, noncompressed, non reverse key B*Tree index It is not possible to create a unique bitmap index (and you wouldn t want to if you could think about the cardinality issue) Indexes are schema objects, and it is possible to create an index in one schema on a table in another, but most people would find this somewhat confusing A composite index is an index on several columns Composite indexes can be on columns of different data types, and the columns do not have to be adjacent in the table TIP Many database administrators do not consider it good practice to rely on implicit index creation If the indexes are created explicitly, the creator has full control over the characteristics of the index, which can make it easier for the DBA to manage subsequently Consider this example of creating tables and indexes, and then defining constraints:
create table dept(deptno number,dname varchar2(10)); create table emp(empno number, surname varchar2(10), forename varchar2(10), dob date, deptno number); create unique index dept_i1 on dept(deptno); create unique index emp_i1 on emp(empno); create index emp_i2 on emp(surname,forename); create bitmap index emp_i3 on emp(deptno); alter table dept add constraint dept_pk primary key (deptno); alter table emp add constraint emp_pk primary key (empno); alter table emp add constraint emp_fk foreign key (deptno) references dept(deptno);
Copyright © OnBarcode.com . All rights reserved.