Hello Dev, welcome to our guide on Sys Tables in SQL Server! As a developer, it’s essential to have a thorough understanding of the system tables in SQL Server. Sys Tables are vital components of a SQL Server Database, and understanding how they function is crucial for database administrators as well. In this guide, we will cover all aspects of Sys Tables, including their uses, benefits, and how to access them. So, without further ado, let’s dive into the world of Sys Tables!
What are Sys Tables in SQL Server?
Sys Tables are system tables that are created and maintained by SQL Server. They contain essential information about the database schema, objects, data, and metadata. These tables store data about database objects such as tables, stored procedures, views, and triggers, etc. Sys Tables are a part of the System Catalog and provide a way for users to query and retrieve metadata about database objects.
The Sys Tables are part of the System Catalog, which is a collection of metadata that describes the database schema. The System Catalog contains information about the tables, views, stored procedures, triggers, and other objects in the database. The Information in the System Catalog is updated automatically by SQL Server and can be accessed using T-SQL queries. In short, Sys Tables are tables that are created by SQL Server to store information about the database schema and objects.
Why are Sys Tables Important?
Sys Tables are essential for developers and database administrators for many reasons. Here are some of the reasons why Sys Tables are important in SQL Server.
Reason |
Description |
|---|---|
Database Documentation |
Sys Tables provide critical information about the database schema and objects that can be used to document the database. |
Database Maintenance |
Database administrators can use Sys Tables to identify and resolve performance and maintenance issues in the database. |
Query Optimization |
Developers can use Sys Tables to optimize SQL queries by identifying tables, indexes, and statistics that are frequently used. |
Data Management |
Sys Tables can be used to manage data in the database by identifying and deleting unused objects, monitoring database growth, and tracking database changes. |
In summary, Sys Tables are vital components of SQL Server and are used for database documentation, maintenance, query optimization, and data management.
How to Access Sys Tables in SQL Server?
Accessing Sys Tables in SQL Server is easy, and there are several ways to do it. Here are some of the methods used to access Sys Tables in SQL Server.
Method 1: Using Object Explorer in SQL Server Management Studio
You can access Sys Tables using Object Explorer in SQL Server Management Studio. Follow these steps:
- Open SQL Server Management Studio and connect to a SQL Server instance.
- Expand the Databases node and select the database you want to view.
- Expand the Tables node, and then the System Tables node.
- Now you can view the list of Sys Tables available in the database.
Method 2: Using T-SQL Query
You can also use T-SQL queries to access Sys Tables in SQL Server. Follow these steps:
- Open SQL Server Management Studio and connect to a SQL Server instance.
- Open a new query window.
- Type the following query to view the list of Sys Tables:
- Execute the query, and you will see the list of Sys Tables available in the database.
SELECT * FROM sys.tables WHERE is_ms_shipped = 0
Understanding Sys Tables
Now that we know what Sys Tables are and why they are essential, let’s look at some of the critical Sys Tables in SQL Server.
Sys.objects
Sys.objects table contains information about all the objects in the database, including tables, views, functions, stored procedures, and triggers. The Sys.objects table is the primary Sys Table in SQL Server and is used extensively for querying and managing database objects. Here are some of the essential columns in the Sys.objects table:
Column Name |
Description |
|---|---|
object_id |
The ID of the object. |
name |
The name of the object. |
type_desc |
The type of the object (table, view, function, stored procedure, or trigger). |
create_date |
The date and time when the object was created. |
Sys.columns
Sys.columns table contains information about all the columns in the database tables. Here are some of the essential columns in the Sys.columns table:
Column Name |
Description |
|---|---|
object_id |
The ID of the object (table or view). |
name |
The name of the column. |
column_id |
The ID of the column. |
system_type_id |
The ID of the system data type. |
max_length |
The maximum length of the column. |
Sys.indexes
Sys.indexes table contains information about all the indexes in the database. Here are some of the essential columns in the Sys.indexes table:
Column Name |
Description |
|---|---|
object_id |
The ID of the object (table or view). |
name |
The name of the index. |
index_id |
The ID of the index. |
type_desc |
The type of the index (clustered or nonclustered). |
is_unique |
Whether the index is unique or not. |
Sys.sysusers
Sys.sysusers table contains information about all the users in the database. Here are some of the essential columns in the Sys.sysusers table:
Column Name |
Description |
|---|---|
uid |
The ID of the user. |
name |
The name of the user. |
createdate |
The date and time when the user was created. |
hasdbaccess |
Whether the user has access to the database or not. |
FAQs
Q1. Can we modify Sys Tables in SQL Server?
No, we cannot modify Sys Tables in SQL Server. These tables are system tables created and maintained by SQL Server, and any modification can lead to database corruption.
Q2. Are Sys Tables available in all versions of SQL Server?
Yes, Sys Tables are available in all versions of SQL Server, including SQL Server 2000, 2005, 2008, 2012, 2014, 2016, 2017 and 2019.
Q3. Can we view Sys Tables in other database management systems?
Sys Tables are unique to SQL Server and cannot be viewed in other database management systems such as MySQL or Oracle Database.
Q4. How can Sys Tables be used for query optimization?
Sys Tables can be used to optimize SQL queries by identifying frequently used tables, indexes, and statistics. Database administrators can use this information to tune the database and improve query performance.
Q5. How often are Sys Tables updated in SQL Server?
Sys Tables are updated automatically by SQL Server whenever there is a change in the database schema, such as adding or modifying tables or columns.
Conclusion
Sys Tables are an essential part of SQL Server and are used extensively by developers and database administrators. They provide vital information about the database schema, objects, data, and metadata. In this guide, we covered all aspects of Sys Tables, including their uses, benefits, and how to access them. We also discussed some of the critical Sys Tables in SQL Server, including Sys.objects, Sys.columns, Sys.indexes, and Sys.sysusers. We hope this guide has been informative and helpful to you. Happy coding!