repeatable read

Lost update: Two transactions update a row of data at the same time, the last transaction update will overwrite the first transaction update, resulting in the first transaction update data loss, which is caused by no lock; 1. Dirty reads: Dirty reading means that when a transaction is accessing the data and the data has been modified, and the modification has not been submitted to the database, another transaction accesses the data and then uses the data.e.g.The original salary for 1.Mary was 1

I. DATABASE TRANSACTION ISOLATION LEVELThere 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. √:

I. Database transaction ISOLATION LEVEL There are 4 isolation levels for database transactions, from low to high to read uncommitted, Read committed, Repeatable read, and Serializable, which can solve the problems of dirty reading, non-repeatable reading, and Phantom readin

1. Some problematic reads in the transaction: dirty read, non-repeatable read, Phantom readThe dirty read (Dirty Read) transaction T1 updated the contents of a row of records, but did not commit the changes. The transaction T2 reads the updated row, and then T1 performs the

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

One, dirty reading, non-repeatable reading, Phantom reading 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.For example:Zhang San's salary was 5000 and transaction a c

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 t

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

is already available. If it is the last room that has not been booked, then this will be a serious mistake. Note: The consequences of dirty reading are serious. 2, not repeatable read. In the same transaction, reading the data again is "your select operation", and the data read is not the same as the data read for th

been booked, then this will be a serious mistake.Note: The consequences of dirty reading are very serious.2, not repeatable read.In the same transaction, when the data is read again "is your select operation", the data read, and the 1th reading of the data, is not the same. is not repeatable reading.As an example:Tran

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 al

lost.2) Dirty read: Dirty read refers to when a transaction is accessing the data, and the data is modified, and this modification has not been committed to the database, then another transaction also accesses the data, and then used this data.For example:Zhang San's salary was 5000 and transaction a changed his salary to 8000, but transaction a was not yet submitted.MeanwhileTransaction B is reading Zhang

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 com

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 co

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,

One, dirty reading, non-repeatable reading, Phantom reading 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. For example: Zhang San's salary was 5000 and transactio

Tags: transaction str oracle REPEATABLE TRANSACTION isolation BLE same commit netThese are issues that arise from transaction concurrency. There are five levels of transaction isolation:Transaction_none does not use transactions.transaction_read_uncommitted allow dirty reads.Transaction_read_committed prevents dirty reads, the most common isolation level, and is the default isolation level for most databasesTransaction_repeatable_read can prevent dirt

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 acc

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.