crystal report barcode font free download Using Histograms in Font

Generator Code 39 Full ASCII in Font Using Histograms

Using Histograms
Drawing Code-39 In None
Using Barcode creation for Font Control to generate, create Code 3 of 9 image in Font applications.
www.OnBarcode.com
Printing DataMatrix In None
Using Barcode creator for Font Control to generate, create Data Matrix 2d barcode image in Font applications.
www.OnBarcode.com
Normally, the CBO assumes that data is uniformly distributed in a table. There are times when data in a table isn t distributed in a uniform way. If you have an extremely skewed data distribution in a table, you re better off using histograms to store the column statistics. If the table data is heavily skewed toward some values, the presence of histograms provides more efficient access methods. Histograms use buckets to represent distribution of data in a column, and Oracle can use these buckets to see how skewed the data distribution is. You can use the following types of histograms in an Oracle database: Height-based histograms divide column values into bands, with each band containing a roughly equal number of rows. Thus, for a table with 100 rows, you d create a histogram with 10 buckets if you wanted each bucket to contain 10 rows. Frequency-based histograms determine the number of buckets based on the distinct values in the column. Each bucket contains all the data that has the same value.
Printing USS-128 In None
Using Barcode maker for Font Control to generate, create GS1 128 image in Font applications.
www.OnBarcode.com
Paint GS1 - 13 In None
Using Barcode generation for Font Control to generate, create GS1 - 13 image in Font applications.
www.OnBarcode.com
Creating Histograms
GS1 - 12 Encoder In None
Using Barcode creator for Font Control to generate, create UPCA image in Font applications.
www.OnBarcode.com
QR Code 2d Barcode Drawer In None
Using Barcode generator for Font Control to generate, create QR image in Font applications.
www.OnBarcode.com
You create histograms by using the METHOD_OPT attribute of the DBMS_STATS procedure such as GATHER_TABLE_STATS, GATHER_DATABASE_STATS, and so on. You can either specify your own histogram creation requirements by using the FOR COLUMNS clause, or use the AUTO or SKEWONLY values for the METHOD_OPT attribute. If you choose AUTO, Oracle will decide which columns it should collect histograms for, based on the data distribution and workload. If you choose SKEWONLY, Oracle will base the decision only on the data distribution of the columns. In the two examples that follow, I use the FOR COLUMNS clause to specify the creation of the histograms.
Creating PDF-417 2d Barcode In None
Using Barcode encoder for Font Control to generate, create PDF 417 image in Font applications.
www.OnBarcode.com
Painting NW-7 In None
Using Barcode printer for Font Control to generate, create Codabar image in Font applications.
www.OnBarcode.com
CHAPTER 19 IM PR OVING DA TA BAS E PERFORM ANC E: S QL QUE RY OPTIMIZA TION
Code39 Generation In None
Using Barcode creation for Office Excel Control to generate, create Code 3/9 image in Microsoft Excel applications.
www.OnBarcode.com
Code 39 Full ASCII Drawer In Objective-C
Using Barcode creation for iPhone Control to generate, create Code 39 image in iPhone applications.
www.OnBarcode.com
The following example shows how to create a height-based histogram while collecting the optimizer statistics: SQL> BEGIN DBMS_STATS.GATHER_table_STATS (OWNNAME => 'HR', TABNAME => 'BENEFITS', METHOD_OPT => 'FOR COLUMNS SIZE 10 Number_of_visits'); END; The following example shows how to create a frequency-based histogram: SQL> BEGIN DBMS_STATS.GATHER_table_STATS(OWNNAME => 'HR', TABNAME => 'PERSONS', METHOD_OPT => 'FOR COLUMNS SIZE 20 department_id'); END;
Printing PDF417 In None
Using Barcode encoder for Online Control to generate, create PDF 417 image in Online applications.
www.OnBarcode.com
Drawing Code-128 In Java
Using Barcode maker for Eclipse BIRT Control to generate, create Code 128 Code Set A image in BIRT reports applications.
www.OnBarcode.com
Viewing Histograms
Barcode Creator In .NET Framework
Using Barcode creator for VS .NET Control to generate, create Barcode image in Visual Studio .NET applications.
www.OnBarcode.com
Print Code39 In Visual Studio .NET
Using Barcode generator for Reporting Service Control to generate, create Code 39 image in Reporting Service applications.
www.OnBarcode.com
You can use the DBA_TAB_COL_STATISTICS view to view histogram information. Following are the two queries that show the number of buckets (num_buckets) and the number of distinct values (num_distinct), first for the height-balanced and then for the frequency-based histogram created in the previous section: SQL> SELECT column_name, num_distinct, num_buckets, histogram FROM USER_TAB_COL_STATISTICS WHERE table_name = 'BENEFITS' AND column_name = 'NUMBER_OF_VISITS'; COLUMN_NAME ----------------NUMBER_OF_VISITS NUM_DISTINCT ------------320 NUM_BUCKETS -----------10 HISTOGRAM --------------HEIGHT BALANCED
GS1 128 Creator In Objective-C
Using Barcode drawer for iPhone Control to generate, create UCC-128 image in iPhone applications.
www.OnBarcode.com
Drawing Matrix 2D Barcode In .NET Framework
Using Barcode printer for ASP.NET Control to generate, create Matrix Barcode image in ASP.NET applications.
www.OnBarcode.com
SQL> SELECT column_name, num_distinct, num_buckets, histogram FROM USER_TAB_COL_STATISTICS WHERE table_name = 'PERSONS' AND column_name = 'DEPARTMENT_ID'; COLUMN_NAME -------------DEPARTMENT_ID NUM_DISTINCT -----------8 NUM_BUCKETS -----------8 HISTOGRAM ---------FREQUENCY
Print EAN 13 In Objective-C
Using Barcode creator for iPhone Control to generate, create EAN / UCC - 13 image in iPhone applications.
www.OnBarcode.com
Data Matrix ECC200 Printer In Java
Using Barcode encoder for Java Control to generate, create DataMatrix image in Java applications.
www.OnBarcode.com
Adaptive Cursor Sharing
Code 128 Code Set B Recognizer In Java
Using Barcode scanner for Java Control to read, scan read, scan image in Java applications.
www.OnBarcode.com
Data Matrix 2d Barcode Maker In None
Using Barcode maker for Online Control to generate, create Data Matrix 2d barcode image in Online applications.
www.OnBarcode.com
Although using bind variables improves performance and scalability by reducing parse time and memory usage, literal values actually produce better execution plans than bind values for variables. When you force cursor sharing in the database by setting the CURSOR_SHARING parameter to EXACT or SIMILAR, some SQL statements end up with suboptimal plans for some bind variable values. The CostBased Optimizer may very well create a suboptimal plan if it happens to peek at the bind values and if the bind values used by the first SQL statements to go into the shared pool are unrepresentative of the true values of the variable. Developers and DBA s sometimes resort to setting the unofficial Oracle initialization parameter _OPTIM_PEEK_USER_BINDS (ALTER SESSION SET "_optim_peek_user_binds"=FALSE;) to prevent the database from peeking at the bind values. Adaptive cursor sharing provides a much more elegant way to prevent the optimizer from creating suboptimal execution plans caused by bind peeking. Oracle relies on its bind peeking technique when it first parses a SQL statement. The optimizer will always hard parse a new statement and peek at the bind variable values to get a sense of what the values look like. The initial bind values it sees during the bind peeking have an inordinate influence
Copyright © OnBarcode.com . All rights reserved.