System functions are segregated into how many types will be examples of each type.
System functions are segregated into 13 parts mainly as mentioned below:
1. Aggregate function: functions which are used for any aggregates work. eg: min, max, sum, avg, count etc.
2. Configuration function: Functions relating to server related options such as : @@Language, @@Langid, @@Servername ,@@Servicename
3. Cursor function : functions which are used for the handling cursors such as: @@Cursor_Rows ,@@Fetch_Status
4. Date and time function: functions which are used for computing data in the system : Getdate(), Datepart(), Datename(), Datediff(), Dateadd(), Current_Timestamp, Sysdatetime(), Isdate()
5. Mathematical functions: functions which are used for any mathematical work. eg: Floor() ,Power(), Log(), Degrees(), Ceiling(), Round(), Tan(), Square(), Sqrt(), Power(), Abs()
6. Metadata function: functions which are used for extracting Metadata from the server. eg: Object_Id(), Db_Name(), Col_Name(), Type Property(), @@Procid, Object_Name(), Col_Name()
7. Hierarchy ID function: functions which are used for determining /extracting the Hierarchy eg: ToString(), GetLevel(), GetRoot(), GetAncestor()
8. Row set function: functions which are used for extract/converting the rows from a dataset eg: , Openxml(), Openrowset(), Openxml(), Opendatasource(), Openquery(), Opendatasource()
9. Security function: functions which are used for security of the database, check the current user details, and we can maintain the log from that functions eg: , Is_Member(), User_Id(), User_Name(), User, User_Name()
10. String function functions used for manipulating/ working on the string. Eg: Right(), Ltrim(), Upper(), Lower(), Len(), Left(), Difference(), Charindex(), Patindex(), Replace(), Replicate(), Reverse(), Substring(), Rtrim(), Str(), Stuff()
11. System statistical function: function used to get the statistics/ current state of the server e.g.: @@Total_Read, @@Connections, @@Total_Write, @@Total_Errors, @@Pack_Sent, @@Pack_Received, @@Timeticks, @@Idle, @@Cpu_Busy
12. Text and images function: functions used for text and images e.g.: Patindex(), Textptr(), Textvalid()
13. Other function: some for the functions which are not segregated into any of the parts eg. : Cast(), Convert(), Datalength(), Host_Name(), Isnull(), Nullif(), @@Identity, Session_User, System_User, Scope_Identity(), @@Rowcount,