Oracle database is often used to manage and organize complex and broad swathes of data, and from time to time, developers and administrators may need to gain insight into the size of the tables within this database system. Knowing such details can prove handy in managing the database effectively. This knowledge helps in optimization and it is also beneficial while making decisions related to capacity planning, performance tuning and managing space. This article will focus on the explaining the method of determining table sizes in an Oracle database, walking you through the Oracle SQL code required to retrieve this information.
Getting Table Sizes in Oracle SQL
Here’s a solution to obtain table sizes in Oracle SQL. This information is made readily available through the USER_SEGMENTS data dictionary view, from where it can be obtained by executing a simple query.
SELECT segment_name AS table_name,
segment_type AS table_type,
bytes/1024/1024 AS table_size_mb
FROM user_segments
WHERE segment_type = ‘TABLE’;
This Oracle SQL code allows us to list all tables from an Oracle database along with their sizes expressed in megabytes (MB) for better readability.
Understanding the Oracle SQL Code for Retrieving Table Sizes
To understand how this piece of code functions, it’s important to comprehend the information contained within the user_segments view in Oracle. Oracle uses schemas and database objects –behind the scenes– to arrange data within databases.
The user_segments view refers to such stored data, serving as a representation of the database objects like tables, indexes, etc. It contains information about such segments like table name (segment_name), table type (segment_type), and the space consumed by that table in bytes.
The SQL query fetches this data, filtering the results to only show objects of the type ‘TABLE’. The size of the tables in bytes is converted to megabytes (MB) for convenience.
Additional Oracle SQL Libraries and Functions Involved
The function bytes/1024/1024 is used within the code to convert the size of the tables from bytes to megabytes. This is a simple mathematical operation where the size in bytes is divided by 1024 (the number of bytes in a kilobyte) twice (to get the size in megabytes).
In regard to libraries, the Oracle database system has in-built libraries that help handle the database objects. Inside the user_segments view, Oracle utilizes its in-built library to store and retrieve information about the space that each database object occupies.
Besides, the query makes use of ‘SELECT’, ‘FROM’, and ‘WHERE’ clauses that are part of the SQL language specifications that Oracle’s SQL libraries support. The ‘SELECT’ allows you to specify the data you want to fetch, ‘FROM’ specifies the table from where the data needs to be fetched, and ‘WHERE’ clause is used to filter the records.
Perhaps, a future evolution could be a computation of table sizes as a proportion of the total database size – a measure that can help database administrators better understand the data landscape within their Oracle database.
Maintaining and managing the size of your Oracle database tables become a walk in the park when you know exactly what is happening behind the scenes. It can play a significant role in enhancing database performance and leading to more efficient data management henceforth.
Related Oracle SQL Commands and Views
Besides user_segments, Oracle SQL Database provides a number of other useful views like:
- V$SYSSTAT and V$SESSTAT: They provide statistics on Oracle instance, be it the entire system or particular sessions.
- USER_TABLES: Offers information about the tables owned by the current user.
- DBA_TABLES: Provides information about all tables in the database.
In similar fashion, Oracle SQL has a plethora of commands providing a more granular control over the database. For instance, ‘DESCRIBE’ gives the description of a table structure, while ‘DROP’ removes entire tables.
By leveraging the potential of these commands and libraries in Oracle SQL, one can effectively manage, control and make decisions related to the database with relative ease and accuracy.
