Oracle inside (6)

Transaction 6.1
A transaction is a logical unit of work. It consists of one or more data control statements (DML) or data definition statements (DDL. Oracle provides two
Common transactions: Read-only transactions and read/write transactions. Read-only transactions stipulate that the queried data and queries in the transaction will not occur in the database
The impact of any other transactions. Read/write transactions ensure that the data returned by the query is consistent with the data starting from the query.
Read-only transactions ensure transaction-level read consistency. Such transactions can only contain query statements, but cannot contain any DML statements. In this case,
Only data committed before the start of the transaction can be queried. Therefore, the query can be executed multiple times and the results returned each time are the same.
Read/write transactions provide statement-level read consistency, and such transactions do not see the modifications made by the transactions committed during the query execution.
1) Start the transaction:
When the first SQL statement starts, the transaction starts. When the effect of the transaction is canceled or committed, the transaction ends. SET transaction
It also starts a transaction. Syntax:
SET transaction Parameter