oracle temporary table delete

Oracle Creation and deletion of temporary tables

Oracle database is a commercial database management system that is widely used in large-scale applications. Temporary table is a very useful object type in Oracle. It allows users to quickly implement complex queries and data processing without taking up too much space and modifying basic table data. This article will introduce how to create and delete Oracle temporary tables.

1. Create an Oracle temporary table

The method of creating a temporary table is similar to the method of creating an ordinary table, but you need to add "GLOBAL TEMPORARY" or "LOCAL TEMPORARY" as the temporary table identifier before the table name. symbol.

1. GLOBAL TEMPORARY:

GLOBAL TEMPORARY temporary table is a session-level temporary table. The data in the temporary table will be automatically deleted at the end of the session. If multiple temporary tables with the same name are created in the same session, they also exist independently.

The syntax for creating a GLOBAL TEMPORARY table is as follows:

CREATE GLOBAL TEMPORARY TABLE table_name
(
  column1 datatype [ NULL | NOT NULL ],
  column2 datatype [ NULL | NOT NULL ],
  ...
) [ ON COMMIT { DELETE | PRESERVE } ROWS ];

Among them, the ON COMMIT clause specifies whether to delete or retain the rows of the temporary table when submitting.

2. LOCAL TEMPORARY:

LOCAL TEMPORARY temporary table is a local temporary table. It is only valid within the current transaction and is automatically deleted when the transaction commits or rolls back.

The syntax for creating a LOCAL TEMPORARY table is as follows:

CREATE LOCAL TEMPORARY TABLE table_name
(
  column1 datatype [ NULL | NOT NULL ],
  column2 datatype [ NULL | NOT NULL ],
  ...
) [ ON COMMIT { DELETE | PRESERVE } ROWS ];

2. Delete the Oracle temporary table

The method of deleting the Oracle temporary table is the same as the method of deleting the ordinary table, but please note that The following two points:

1. Because the temporary table is a special table, it must be deleted using a specific operation method. For GLOBAL TEMPORARY tables, you should first use the TRUNCATE TABLE statement to clear the rows in the table, and then use DROP TABLE to delete the table itself. For LOCAL TEMPORARY tables, you only need to use the DROP TABLE statement.
2. Be careful when deleting temporary tables to avoid accidentally deleting temporary tables created by other users or accidentally deleting them when deletion is not required.

The following is the specific method of deleting Oracle temporary tables.

1. Delete the GLOBAL TEMPORARY temporary table

When deleting the GLOBAL TEMPORARY temporary table, you first need to use the TRUNCATE TABLE statement to delete all rows in the table. The TRUNCATE TABLE statement quickly and safely deletes all data in a table. If you omit this step, you will not be able to delete the temporary table itself.

The operation syntax of TRUNCATE TABLE is as follows:

TRUNCATE TABLE table_name;

Next, use the DROP TABLE statement to delete the temporary table itself. The syntax of DROP TABLE is as follows:

DROP TABLE table_name;

2. Delete LOCAL TEMPORARY temporary table

When deleting LOCAL TEMPORARY temporary table, just use the DROP TABLE statement. The syntax of DROP TABLE is as follows:

DROP TABLE table_name;

3. Notes

When using Oracle temporary tables, you should pay attention to the following matters:

1. The name of the temporary table should have Uniqueness to avoid naming conflicts with other existing ordinary or temporary tables.
2. After completion of use, the temporary table should be deleted in time to free up space and avoid impact on other operations.
3. For the GLOBAL TEMPORARY temporary table, since its data is automatically deleted after the session ends, when using it, you should ensure that all the required data is queried before the session ends.
4. The use of temporary tables should follow database best practices to ensure data integrity and validity.

Summary

This article introduces the creation and deletion methods of Oracle temporary tables. Temporary tables are a very useful database object type that can help users quickly implement complex queries and data processing without modifying basic table data and taking up too much space. When using temporary tables, you should pay attention to the uniqueness of the naming, timely deletion and follow best practices to ensure the integrity and validity of the data to give full play to its role.

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