by index

In 11g, oracle introduced a new feature: adaptive cursor sharing. This feature is mainly used to improve the execution plan of SQL statements with variable binding. It also causes SQL statements with variable binding to generate multiple cursors. In

Oracle index access method, unique index scan, unique index is a single match. In a unique index, each non-null key value has only one unique key and the primary key is also the unique index. Oracle index access method, unique index scan, unique

SQLPLUS AutoTrace is a simple and convenient tool for analyzing SQL Execution plans and execution efficiency. In most cases, it is also a very useful tool. Use AutoT SQLPLUS AutoTrace is a simple and convenient tool for analyzing SQL Execution plans

In web development, the need to reflect changes in the data in real time to the UI requires manipulation of the DOM, but complex or frequent dom operations are often the cause of performance bottlenecks, and react introduces the virtual DOM

Identification of external and internal tables connected by nested oracle Loops SQL> create table a1 as select * from all_objects ; Table created SQL> select count(*) from a1;   COUNT(*) ----------      49708 SQL> create table a2 as select * from a1

When some tables in the system have highly uneven data distribution, the use of a bar chart can produce better selective evaluation, resulting in a more optimized execution plan. A bar chart provides an effective and simple way to present data

1. Enable event tracking 10046Alter session set events '2017 trace name context forever, level 12 '; 2. Execute an SQL statement at Will (we will find the execution of this SQL statement in the trace file)Select * from dba_users where username = 'hr

In 11g, Oracle introduced a new feature: adaptive cursor sharing. This feature is mainly used to improve the execution plan of SQL statements with variable binding. It also causes SQL statements with variable binding to generate multiple cursors. In

Use sqlprofile to optimize slow SQL statements in goldengate and SQL statements In HP unix, a process is monitored to occupy a high cpu. Later, it was found that the statement execution plan in gg had a problem, resulting in a high cpu. Since the

Vector usage in JAVAJava. util. Vector provides a Vector class to implement functions similar to dynamic arrays. There is no pointer concept in the Java language, but correct and flexible use of pointers can indeed greatly improve the quality of the

All the methods of JS string Formcharcode:String.formcharcode (";>>>>>>") "7"The Unicode code returns the corresponding string. CharAt:var str= "Hello World"; Str.charat (0);>>>>> "H"; returns the corresponding string by index, the range is

A primer1 What is data?　　x=10,10 is the data we want to store.2 Why data is divided into different typesData is used to represent States, and different States should be represented by different types of data.3 Data typesNumbers (shaping, long-shaped,

Openpyxl Xlrd Xlwt The limitations of XLWT when working with Excel data – you cannot write more than 65535 rows, 256 columns of data (because it supports only Excel 2003 and previous versions, there is this limit for the number of rows

List: Python one of the underlying data types Other languages also have a list of concepts,js--> arrays, indexable, can be sliced, can be added in step A list can store a large amount of data 32-bit Python is limited to 536,870,912

Oracle in RowNum The number of the row returned from the query, the first row returned is 1, the second row is 2, and so on, this pseudo field can be used to limit the total number of rows returned by the query, and rownum cannot be prefixed with

1.1.1 Summary If you want to optimize the database, we can mainly through the following five ways to optimize the database system. 1. Computer Hardware tuning 2. Application Tuning 3. Database Index Optimization 4. SQL statement Optimization 5.

Java.util.vector provides vector classes (vectors) to implement functions similar to dynamic arrays. There is no concept of pointers in the Java language, but if you use pointers correctly and flexibly, you can actually improve the quality of your

SELECT * from A,b where a.id Sort Merge Join (Sortmerge join) The preceding article mentions nested loops and hash joins, and they all have a driver table concept. Sort Merge Join no driver table one says that two table/row sources are

Explain plan for SELECT * from Comr_clerk_vou c where C.vou_type = ' one ' and C.sub_vou_type = ' 0 ' and c.vou_ Status like '%0% '; ACC SELECT * FROM table (Dbms_xplan.display ()); ---drop index comr_clerk_vou_idx3; ---CREATE INDEX

1. INDEX RANGE SCAN--Please remember this index RANGE scan scanning methoddrop table T Purge;CREATE TABLE T as select * from Dba_objects;Update T set object_id=rownum;CommitCREATE index idx_object_id on T (object_id);Set Autotrace traceonlySet