Published on

October 26, 2006

Exploring SQL Server Concepts: Table Variables vs Temporary Tables

SQL Server offers various features and tools to handle data manipulation and processing efficiently. In this article, we will discuss the differences between table variables and temporary tables, and when to use each of them.

Table Variables

Table variables were introduced in SQL Server 2000 and are suitable for all set-based operations. They follow the scope rules applicable to variables and do not have a physical representation in the database. This means that they do not carry the baggage related to transaction isolation, locking, and logging.

One advantage of using table variables is that they can result in fewer recompilations compared to temporary tables. This can lead to improved performance in certain scenarios. Additionally, table variables can be used within functions, and their results can be accessed outside of the function.

However, there are some limitations to using table variables. They cannot be used in situations where the output of a stored procedure needs to be stored directly into a table variable. In such cases, an intermediary table, such as a temporary table, needs to be used.

Temporary Tables

Temporary tables have a physical representation in the database and are useful for storing data temporarily during a session. They are created with a unique name and can be accessed by multiple users simultaneously. However, this can lead to scalability issues as the number of users increases.

Temporary tables are suitable for storing large amounts of data and can be used in stored procedures. They provide transaction isolation, locking, and logging capabilities. However, they may result in more recompilations compared to table variables.

Choosing Between Table Variables and Temporary Tables

When deciding whether to use table variables or temporary tables, consider the following:

  • Use table variables when you need to perform set-based operations and want to avoid the overhead of transaction isolation, locking, and logging.
  • Use temporary tables when you need to store large amounts of data temporarily or when you require transaction isolation, locking, and logging capabilities.
  • Consider the scalability of your application when using temporary tables, as each user will have their own copy of the table.
  • Be aware of the limitations of table variables, such as the inability to directly store the output of a stored procedure.

In conclusion, both table variables and temporary tables have their own suitable applications. Table variables are ideal for set-based operations and can result in improved performance, while temporary tables are useful for storing large amounts of data temporarily and provide transaction isolation capabilities. Choose the appropriate option based on your specific requirements and consider the limitations of each.

Thank you for reading!

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