oracle sql for dummies

not be indexed, the field has only 8 values, the index value is highly repeatable, the index selectivity is significantly lower, and therefore no index is built." However, the distribution of data values on this field is very special, as shown in the following table: Range of values The 6 7 % of total data 1% 98% 1% Moreover, in the common query, the query disposalcourseflagEighth Palm use hint to force the specified indexU

Introduction: Oracle DatabaseThere is no constraint. Oracle databases must comply with certain rules. As we all know, few of us work in isolation; most PL/SQL development work is carried out in a relatively large organization. But we basically work with our own device in our own compartment. Almost no PL/SQL developmen

Today, we will introduce how to correctly use Oracle SQL Trace and 10046 event to diagnose the performance of Oracle databases, we all know that level over 1 10046 events are often referred to as extended SQL trace, which is usually used to diagnose the performance problems of a single

The Oracle tutorial you are looking at is the development of high-performance, dynamic SQL programs based on Oracle. Absrtact: The development of dynamic SQL program is summarized, and some development techniques are given according to the author's actual development experience.Key words: Dynamic

Before executing an SQL statement, Oracle needs to first check the SQL Execution Plan and then execute the SQL statement according to the execution plan. The optimizer is responsible for analyzing the execution plan, under different conditions, an SQL statement may have mult

oracle| Performance | optimization 1. Choose the appropriate Oracle Optimizer There are 3 Oracle optimizer types: A. Rule (rule-based) b. Cost (based on costs) c. CHOOSE (optional) Set the default optimizer to pass various declarations of optimizer_mode parameters in the Init.ora file, such as Rule,cost,choose,all_rows,first_rows. You will of course o

Tags: Oracle performance databaseWhen Oracle queries come with efficiency issues, we often need to understand the problem so that we can solve the problem. Oracle provides trace information for SQL execution, which contains textual information about SQL statements, some exec

SQL Optimization Tips (1):Connection order in the WHERE clause: Oracle parses the WHERE clause in a bottom-up order, and according to this principle, the connections between tables must be written before other where conditions, those that can filter out a large number of recordsMust be written at the end of the WHERE clause.For exampleInefficient: SELECT * from Report_sale_account Ewhere hsje>5000and DZXL =

ORACLE provides two types of SQL optimizer: CBO and RBO. CBO was introduced in ORACLE7, but it was only mature in ORACLE8i. ORACLE has explicitly stated thatIn later versions (ORACLE 10G), RBO will no longer be supported. Therefore, selecting CBO is an inevitable trend. CBO and RBO, as different

Tags: china-pub computer OracleThis is a high quality pre-sale recommendation of Computer class OCA Certification Exam Guide (1z0-061) Oracle Database 12c SQL Foundation ". Oracle Certified Master (OCM) 's latest work, the OCA Certification exam official book, covers all OCA goals for the 1z0-061 exam. Content Introduction the OCA Certification Exam Guide (1z

If you want to improve the actual execution efficiency of SQL statements in Oracle databases, you must first optimize the business logic of your actual application, in the following articles, Oracle also provides some technical methods. Today we will mainly talk about three methods: Oracle provides a variety of methods

the contents of the SQL buffer to check if your modifications are correct. Example 3-8 Sql> L Example 3-8 results Example 3-8 results table name The changes you made are accurate. So how do we run this statement?3.4 '/' (RUN) commandYou certainly do not need to reenter this statement because this statement is already in the SQL buffer.

Oracle SQL statement optimization, oraclesql statement Although orm ing is used in the project, the optimization of the Oracle system is very valuable. Here we will summarize the commonly used statements from the perspective of SQL statements. 1. Optimization in the from field:Oracle installs table data from the right

The Oracle tutorial being looked at is: Oracle SQL Performance Tuning series learning one. 1. Choose the appropriate Oracle OptimizerThere are 3 Oracle optimizer types:A. Rule (rule-based) b. Cost (based on costs) c. CHOOSE (optional)Set the default optimizer to pass various

Assume that you have a network ordering system based on Microsoft. NET, but the QC maintenance system still uses an old Oracle database application. If your customer places an order such as product replacement during the warranty period, the order will not be charged. In this case, you need to obtain real-time query results from the Oracle database. By establishing a link server (linked Server), you can que

Oracle 11g PL/SQL function result cache, oracle11g Two experiments have been conducted to simulate the Oracle Performance Diagnosis art. The book says that if you don't need RELIES_ON, then the changes to the objects on which the function depends will not result in the invalid result cache operation (result_cache RELIES_ON (test1, test2). The test proves that thi

The ORACLE tutorial is: Oracle uses PL/SQL to operate COM objects. PL/SQL is a specialized language for programming in Oracle databases. It is a third-generation procedural programming language. Starting from Oracle8, the external C language calling process is provided direc

Using Notepad ++ to Execute Oracle SQL, executeoracle Link: http://www.toadworld.com/products/toad-for-oracle/ B /weblog/archive/2013/08/21/using-notepad-to-execute-oracle-sql.aspx Notepad ++ is a very useful text editing tool. It is also very interesting to use it to execute Oracl