Characteristics of SQL Server things

ACID

1. Atomicity (atomicity), atomicity means that transactions in a database are executed as atoms. That is, the entire statement is either executed or not executed.
2. Consistency (consistency), consistency, that is, the integrity constraints of the database are not compromised until the transaction begins and after the transaction has ended.
3. Isolation (isolation), the execution of a transaction is non-disruptive, and a transaction cannot see the data in the middle of a time when other transactions are running.

The easy question is: dirty reads (one thing reads uncommitted data from another thing)

Non-repeatable read (two identical queries within a range of objects return different data)

Phantom Read (a phenomenon that occurs when a transaction is not executed independently, such as when the first transaction modifies data in a table that involves all rows of data in the table.) At the same time, the second transaction modifies the data in the table by inserting a new row of data into the table.    Then the user who will be working on the first transaction in the future finds that there are no modified rows of data in the table, as if the illusion had occurred. ）

4. Persistence (durability) means that after the transaction is completed, the changes made to the database by the firm are persisted in the database and are not rolled back.

Characteristics of SQL Server things