How to Use Or Create Temporary Table In Oracle?

In Oracle, temporary tables are created using the CREATE GLOBAL TEMPORARY TABLE statement. These tables are similar to regular tables, but they are only visible to the session that created them and their data is automatically deleted when the session ends.

To create a temporary table in Oracle, you would use the following syntax:

CREATE GLOBAL TEMPORARY TABLE temp_table_name ( column1 datatype, column2 datatype, ... );

After creating the temporary table, you can use it just like a regular table to insert, update, delete, and select data.

To use an existing temporary table in Oracle, you would simply reference it in your SQL queries just like you would with a regular table.

Temporary tables are useful for storing intermediate results or temporary data within a specific session without affecting other sessions or the overall database. Just keep in mind that the data in a temporary table is only available for the duration of the session that created it.

How to create a temporary table in Oracle?

To create a temporary table in Oracle, you can use the CREATE GLOBAL TEMPORARY TABLE statement. Here is an example of how to create a temporary table in Oracle:

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CREATE GLOBAL TEMPORARY TABLE temp_table
(
  id NUMBER,
  name VARCHAR2(50)
)
ON COMMIT DELETE ROWS;

In this example, we are creating a temporary table named temp_table with two columns: id and name. The ON COMMIT DELETE ROWS clause specifies that the data in the temporary table will be deleted when the transaction is committed.

You can now insert data into the temporary table and query it just like a regular table. Keep in mind that the data in the temporary table will only be available for the duration of the session in which it was created.

How to filter data in a temporary table in Oracle?

To filter data in a temporary table in Oracle, you can use a SELECT statement with a WHERE clause to specify the filtering criteria. Here is an example:

1. Create a temporary table:

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CREATE GLOBAL TEMPORARY TABLE temp_table (
   id NUMBER,
   name VARCHAR2(50)
) ON COMMIT DELETE ROWS;

1. Insert data into the temporary table:

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INSERT INTO temp_table (id, name) VALUES (1, 'John');
INSERT INTO temp_table (id, name) VALUES (2, 'Jane');
INSERT INTO temp_table (id, name) VALUES (3, 'Bob');

1. Filter the data in the temporary table:

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SELECT * FROM temp_table WHERE id = 1;

This SELECT statement will retrieve the row with id=1 from the temporary table. You can add any other conditions in the WHERE clause to further filter the data based on your requirements.

What is the performance impact of using temporary tables in Oracle?

Using temporary tables in Oracle can have a performance impact, both positive and negative.

Positive impacts:

1. Improved query performance: Temporary tables can help improve query performance by reducing the amount of data that needs to be processed and reducing the number of times data needs to be accessed from the original tables.
2. Better memory usage: Temporary tables can reduce memory usage by storing intermediate results in memory instead of keeping them in the original tables.

Negative impacts:

1. Overhead: Creating and managing temporary tables can add overhead to the database system, especially if the temporary tables are large or frequently used.
2. Disk I/O: Storing data in temporary tables on disk can increase disk I/O and slow down query performance, especially if the temporary tables are not properly indexed.
3. Locking and contention: Using temporary tables can lead to locking and contention issues, especially in a multi-user environment, where multiple users are trying to access and modify the same tables.

Overall, the performance impact of using temporary tables in Oracle depends on various factors such as the size of the data, the complexity of the queries, the indexing of the tables, and the overall system configuration. It is important to carefully consider the use of temporary tables and optimize their usage to minimize any negative impacts on performance.