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foreword
[SQL development practical skills] series (forty-six): Oracle12C commonly used new features ☞ session-level sequence and data pump (DataPump enhancement) supports exporting views like tables
1. DataPump Enhancement
- Disable logging option (DISABLE_ARCHIVE_LOGGING)
- Export views like tables
2. Session-level sequence
- the case
Summarize

foreword

This article mainly explains the new features of Oracle12C+: In Oracle12C, the data pump (DataPump) has been enhanced, and TRANSFORMthe parameters of Impdp have been expanded to include DISABLE_ARCHIVE_LOGGINGoptions. The default value for this option is "N" and does not affect logging behavior. Set this option to "Y", which will make the table and index set the date index attribute to before importing NOLOGGING, thereby reducing the generation of related logs during import, and reset the log attribute to after importing LOGGING. VIEWS_AS_TABLESparameter allows to export the view as a table. The table structure matches the view columns, and the view query results correspond to the table data.

[SQL development practical skills] This series of bloggers writes as a review of old knowledge. After all, SQL development is very important and basic in data analysis scenarios. Interviews will often ask about SQL development and tuning experience. I believe that when I finish writing this A series of articles can also gain something, and you can also face SQL interviews with ease in the future~.

[SQL development practical skills] series (forty-six): Oracle12C commonly used new features ☞ session-level sequence and data pump (DataPump enhancement) supports exporting views like tables

1. DataPump Enhancement

Disable logging option (DISABLE_ARCHIVE_LOGGING)

The parameters of impdp TRANSFORMhave been extended to include DISABLE_ARCHIVE_LOGGINGoptions. The default value for this option is "N" and does not affect logging behavior. Set this option to "Y", which will make the table and index set the date index attribute to before importing NOLOGGING, thereby reducing the generation of related logs during import, and reset the log attribute to after importing LOGGING.

TRANSFORM=DISABLE_ARCHIVE_LOGGING:Y

The effect can be limited to a specific object type by appending the object type ( TABLE or INDEX).

TRANSFORM=DISABLE_ARCHIVE_LOGGING:Y:TABLE
TRANSFORM=DISABLE_ARCHIVE_LOGGING:Y:INDEX

Export views like tables

VIEWS_AS_TABLESparameter allows to export the view as a table. The table structure matches the view columns, and the view query results correspond to the table data.

VIEWS_AS_TABLES=[schema_name.]view_name[:table_name],...

case:

CONN scott/tiger
CREATE VIEW emp_v AS
 SELECT * FROM emp;

Export VIEWS_AS_TABLESa view with parameters.

$ expdp scott/tiger views_as_tables=scott.emp_vdirectory=test_dir dumpfile=emp_v.dmp logfile=expdp_emp_v.log

By default, Expdp creates a temporary table as a copy of the view, but does not contain data, but only provides a metadata source for export. Alternatively, an appropriately structured table can be determined instead. But maybe this only makes sense on read-only libraries.

2. Session-level sequence

In 12c it is now possible to create new session-level database sequences to support session-level sequence values. These types of sequences work best with session-level global temporary tables. A session-level sequence produces a unique range of values that are bounded within the session, not beyond. Once the session is terminated, the state of the session sequence also disappears.

the case

SQL>create sequence session_seq start with 1 increment by 1 session;
Sequence created
SQL> select DBMS_METADATA.GET_DDL('SEQUENCE','SESSION_SEQ','TEST') from dual;
DBMS_METADATA.GET_DDL('SEQUENCE','SESSION_SEQ','TEST')
-------------------------------------------------------------------
CREATE SEQUENCE"TEST"."SESSION_SEQ"MINVALUE1MAXVALUE 9999999999999999

For session-level sequences, CACHE, NOCACHE, ORDERthe or NOORDERstatement is ignored:

SQL> create sequence session_seq_test start with 1 increment by 1 session cache 20 order;
Sequence created
SQL>selectDBMS_METADATA.GET_DDL('SEQUENCE','SESSION_SEQ_TEST','TEST') from dual;
DBMS_METADATA.GET_DDL('SEQUENCE','SESSION_SEQ_TEST','TEST')
---------------------------------------------------------------------
CREATE SEQUENCE"TEST"."SESSION_SEQ_TEST"MINVALUE1MAXVALUE 99999999999

Test a session-level sequence;
session 1:

SQL> select session_seq.nextval from dual;
   NEXTVAL
----------
         1
SQL> select session_seq.nextval from dual;
   NEXTVAL
----------
         2

Session 2:

SQL> select session_seq.nextval from dual;
   NEXTVAL
----------
         1

It can be seen that the value of the sequence only SESSIONaffects the level, and you can ALTER SEQUENCEset a sequence to the global or session level through the command, as follows to modify the sequence to global. The sequence value will restart from the initial value, and open another session 3 to perform the following operations:

SQL> select session_seq.nextval from dual;
   NEXTVAL
----------
         1
SQL> select session_seq.nextval from dual;
   NEXTVAL
----------
         2
SQL> ALTER SEQUENCE session_seq GLOBAL;
Sequence altered
SQL> select session_seq.nextval from dual;
   NEXTVAL
----------
         1
SQL> select session_seq.nextval from dual;
   NEXTVAL
----------
         2

Modifying the sequence from global to session level through ALTER SQEUENCEthe command is different from modifying the sequence from session level to global. When modifying the sequence from global to session level, the value of the sequence will not be reinitialized, but will be based on the previous sequence of the current session value, do the following test in session three.

SQL> ALTER SEQUENCE session_seq session;
Sequence altered
SQL> select session_seq.nextval from dual;
   NEXTVAL
----------
         3

The result of the previous session three query is 2, sessionafter modifying the global level, it is checked again nextvalas 3.

[SQL development practical skills] series (forty-six): Oracle12C commonly used new features ☞ session-level sequence and data pump (DataPump enhancement) supports exporting views like tables

Series Article Directory

Article directory

foreword

[SQL development practical skills] series (forty-six): Oracle12C commonly used new features ☞ session-level sequence and data pump (DataPump enhancement) supports exporting views like tables

1. DataPump Enhancement

Disable logging option (DISABLE_ARCHIVE_LOGGING)

Export views like tables

2. Session-level sequence

the case

Summarize

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