What are the two main types of temporary tables?

There are 2 types of Temporary Tables: Local Temporary Table, and Global Temporary Table.

What is a temporary table in Teradata?

Temporal tables store and maintain information with respect to time. Using temporal tables, Teradata Database can process statements and queries that include time-based reasoning. As rows are changed in temporal tables, the database automatically creates new rows as necessary to maintain the time dimensions.

What is the difference between a permanent and temporary table Teradata?

Permanent storage of tables is necessary when different sessions and users must share table contents. When tables are required for only a single session, we can request the system to create temporary tables. When the session ends, the system automatically drops the temporary table.

What is the difference between global and local temp tables?

Local temporary tables are deleted after the user disconnects from the instance of SQL Server. Global temporary tables are visible to any user and any connection after they are created, and are deleted when all users that are referencing the table disconnect from the instance of SQL Server.

What is magic table in SQL?

Magic tables are the temporary logical tables that are created by the SQL server whenever there are insertion or deletion or update( D.M.L) operations. The recently performed operation on the rows gets stored in magic tables automatically. These are not physical table but they are just temporary internal tables.

How do you find temporal tables in Teradata?

Columns

DatabaseName – name of the period.
TableName – temporal table schema name.
TemporalType – type of temporal table. System-versioned system-time table. Bitemporal table. Temporal table not system-versioned.

What is a temporal table?

A system-versioned temporal table is a type of user table designed to keep a full history of data changes to allow easy point in time analysis. These period columns are used exclusively by the system to record period of validity for each row whenever a row is modified.

What is the difference between a set table and a MULTISET table in Teradata?

Set Versus Multiset Teradata classifies the tables as SET or MULTISET tables based on how the duplicate records are handled. A table defined as SET table doesn’t store the duplicate records, whereas the MULTISET table can store duplicate records.

What is the difference between global temporary tables and volatile temporary tables?

The difference to the VOLATILE Table is that the Table Definition (DDL) is stored in the Data Dictionary. Global Temporary Tables also survive a system restart (volatile tables are lost). Teradata does not use spool space for global temporary tables as it does for volatile tables, but temp space.

How does compression work in Teradata?

Compression is used to reduce the storage used by the tables. In Teradata, compression can compress up to 255 distinct values including NULL. Since the storage is reduced, Teradata can store more records in a block. This results in improved query response time since any I/O operation can process more rows per block.

How do you create a global temp table?

A global temporary table is created using CREATE TABLE statement with the table name prefixed with a double number sign (##table_name). In SQL Server, global temporary tables are visible to all sessions (connections). So if you create a global temporary table in one session, you can start using it in other sessions.

Where are global temporary tables stored in Teradata?

Global Temporary Tables were also introduced in release V2R3 of Teradata. Their table and column definition is stored in the DD, unlike volatile tables. The first SQL DML statement to access a global temporary table, typically an INSERT/SELECT, materializes the table. They are often called global tables.

What are the different table types in Teradata?

Teradata supports the following table types to hold temporary data. Derived tables are created, used and dropped within a query. These are used to store intermediate results within a query.

How to see the number of volatile tables in Teradata?

The only way to see how many and which volatile tables exist is to use the following command: The main disadvantage of a volatile table is that it must be created via the CREATE VOLATILE TABLE statement every time a new session is established. This situation can be overcome using a global temporary table.

How to build a derived table empsal in Teradata?

The following example builds a derived table EmpSal with records of employees with salary greater than 75000. When the above query is executed, it returns the employees with salary greater than 75000.

What are the two main types of temporary tables? There are 2 types of Temporary Tables: Local Temporary Table, and Global Temporary Table. What is a temporary table in Teradata? Temporal tables store and maintain information with respect to time. Using temporal tables, Teradata Database can process statements and queries that include time-based reasoning. As…