best ebooks to read

The company originally in the Import Execel file, is an import; that is, each import file should have corresponding Java code to achieve, so in the reading Execel file when there is no problem, these two days, ready to waste the previous practice, unified encapsulation, To be able to parse all the Execel files and return the results as long as the configuration file is available. In the implementation process, just started with the demo, so the Execel file is a full path (similar to C://test/xxx

Ext: http://blog.csdn.net/fatherican/article/details/44966921 1, Dirty Read One transaction reads another transaction, and the pending modification is dirty read. Here's the so-called modification, in addition to the update operation, do not forget, but also includeInsert and delete operations. Consequences of dirty reading: If the latter transaction is rolled back, all changes made to it will be revoked.

4 attributes of a database transaction:Atomicity (atomic): both succeed or fail;Consistency (consistency): After a transaction operation, the database is in the same state as the business rules; for example, after the A,b account transfers, the total amount remains unchanged;Isolation (Isolation): transactions in operations do not affect each other;Persistence (Durability): After a transaction is committed, it is persisted to the database. Dirty read,

Issues arising from transaction concurrency:Dirty reads: One transaction reads data that is not committed by another transactionTransaction 1: Updating a single piece of dataTransaction 2: Read record of transaction 1 updateTransaction 1: Commit commits are calledAt this point, the data read by transaction 2 is data stored in database memory, called dirty reads.The data

1. Dirty read : Dirty read refers to when a transaction is accessing the data, and the data has been modified, and this modification has not been committed to the database, then another transaction also accesses the data, and then used this data. 2. Non-repeatable reads : Refers to the same data that is read multiple times within a transaction. When this transact

Original: http://www.cnblogs.com/phoebus0501/archive/2011/02/28/1966709.html Dirty reading is that the data has not been submitted (not necessarily a successful commit), it was used by other affairs.1. Dirty Read : Dirty read refers to when a transaction is accessing the data, and the data has been modified, and this modification has not been committed to the database, then another transaction also accesses

1, Dirty ReadA transaction is read to another transaction, and a modification that has not yet been committed is a dirty read. Here are the so-called modifications, in addition to the update operation, do not forget that also includesInsert and delete operations.The consequences of dirty reads: If the latter transaction is rolled back, all of its modifications will be revoked. The data that the previous tra

Label:Article Source: http://www.bkjia.com/sjkjc/806530.html The database's dirty reads, non-repeatable reads, and Phantom reads are all related to the isolation of the transaction. So first look at the 4 major features of the transaction.4 Characteristics of the transaction (ACID): Atomicity (atomicity): A transaction is a logical unit of work for a database, and its modifications to the database are either all executed or not executed at all. Consistency (CONSISTEMCY): Before and

Let's start with a big picture: SQL statement used: bys@ ocm1>select dbms_rowid.rowid_relative_fno (ROWID) file#,dbms_rowid.rowid_block_number rowid (Block#,deptno) From Bys.test; file# block# DEPTNO ---------- ---------- ---------- 4 391 10 As an example of the above diagram, the text description analyzes the process of obtaining the required data blocks when the foreground process issues a query statement: Note: This article does not involve the parsing part of SQL statements, client

1. Read all strings separated by spaces in the specified file. # Include Ifstream indata; // For the file Indata. Clear (); String filename;Filename = "primes.txt "; Indata. Open (filename. c_str ());String temp_word; // You can also directly read the integer data int temp_word here;// Indata> temp_word; While (indata. EOF ()) // If the file contains a line break, you need to use while (indata. Good ()

mysql> set global read_only=0; Query OK, 0 rows Affected (0.00 sec) mysql> show variables like '%read_only% '; +------------------+-------+ | Variable_name | Value | +------------------+-------+ | innodb_read_only | Off | | read_only | Off | | tx_read_only | Off | +------------------+-------+ 3 rows in Set (0.00 sec) mysql> set global read_only=1; Query OK, 0 rows Affected (0.00 sec) mysql> show variables like '%read_only% '; +------------------+-------+ | Variable_name

There are a large number of computers, technologies and other e-books to download, the speed is good, hope to help friends! The purpose of reading books is usually two. One is to acquire knowledge, and the other is to entertain and relax. As the Internet develops, reading has gradually become a new digital media platform-ebook. In this article,We have collected 35 free English e-books for you to read online and provide free download websites,Do not m

Dirty Read, Phantom Read, and non-repeatable READ + transaction ISOLATION level 1. Dirty read: Dirty read refers to when a transaction is accessing the data, and the data has been modified, and this modification has not been committed to the database, then another transac

Tags: presence IDT does not appear height made Zab repeated modificationsI. Isolation levels and phenomena There are 4 levels of database isolation Read uncomitted, unauthorized reading Read Committed, authorized to read REPEATABLE Read, repeatable reading Serializable, serialization There are 3 types of inconsistenci

Tags: count set InnoDB Department CTI hard disk redo log independently completedThere are four transaction isolation levels for Mysqlinnodb: ( default is repeatable read REPEATABLE read) UNCOMMITTED Read Uncommit : The data was modified in another transaction but not yet committed, and in this transaction the SELECT statement may query for these uncommitted data

1. Physics reading (physical read) When the data block is first read, it will be cached in the buffer cache, while the second read and modify the data block in memory buffer cache The following is an example: 1.1 First read: C:\Documents and Settings\paul yi>sqlplus "/as sysdba" Sql*plus:release 9.2.0.4.0-production on

Read behavior is a condition that can be encountered when multiple transactions are executing concurrently, while reading data. Understanding them first helps you understand the meaning of each isolation level. These include dirty reads, non-repeatable reads, and Phantom reads.Dirty read:Dirty read also known as invalid data readout, refers to in the database access, transaction T1 a value modification, and

Isolation level of a database transactionThere are 4 isolation levels for database transactions, from low to high, READ UNCOMMITTED,Read Committed,Repeatable read, andSerializable, which can be resolved individually by each of the four levels Problems such as dirty reading, non-repetition reading, and Phantom reading. 1. READ