Oracle database transaction related "Weber products must be a boutique"

2. The concept of a transaction:
   Transaction: A transaction consists of a set of DML statements that make up a logical operation

   The transaction begins with an end, and the transaction begins with a DML statement, ending with conmmit and rollback.
   The following situation causes the transaction to end:

   1. Execute commit or ROLLBACK statement

   2. Executing DDL or DCL statements

   3. User exits

   4. System crashes

4. a transaction can contain the following statements:

   1. DML statements that make consistent changes to the data

   2. A DDL statement

   3. A DCL statement

6. the process of DDL and DCL statement execution:

   1. Make a commit first;

   2. Performing DML operations on a data dictionary

   3. If successful, commit, if failed, rollback

8. ensure consistency of data: No data submitted, no other users can see

   Check for changes in data before the data is permanently changed

   Grouping logical-related operations

10. Controlling things: Save points (SavePoint)

11. Sql>Select* fromT; EMPNO ename JOB MGR hiredate SAL COMM DEPTNO----- ------ --------- ----- --------- ----- ----- ------7369ALLEN salesman7902  --dec- the   the            -    1Y -    2W -SQL>savepoint S1; SavePoint created. SQL> INSERT into T (empno,ename) VALUES (3,'b'); 1row created. SQL>savepoint S2; SavePoint created. SQL>delete T;4rows deleted. SQL>Select* fromt; no rows selected SQL>rollback to savepoint S2; Rollback complete. SQL>Select* fromT; EMPNO ename JOB MGR hiredate SAL COMM DEPTNO----- ------ --------- ----- --------- ----- ----- ------7369ALLEN salesman7902  --dec- the   the            -    1Y -    2W -    3B -SQL>rollback to savepoint S1; Rollback complete. SQL>Select* fromT; EMPNO ename JOB MGR hiredate SAL COMM DEPTNO----- ------ --------- ----- --------- ----- ----- ------7369ALLEN salesman7902  --dec- the   the            -    1Y -    2W -----here to notice ah, because rollback to the S1 This save point, also can not be in rollback to S2 this savepoint---because S1 in this save point is not recorded to S2 savepoint information----SQL>rollback to savepoint s2;rollback to savepoint S2*ERROR at line1: ORA-01086: savepoint'S2'Never established