have doubt

Dinesh baabu

10y1kSQL

Hi ,

I have doubt in sql , which primary key ...can you please briefly explain about this ? I am confused in this part ...

My question is ;

1. How can I find this is primary key ?

2. Is it possible to get NULL value in primary ? why ?

3. Which of the scenarios are inserted in CR_DB , CR_ARCHIVE,AND CR_ERROR ?

4. Primary Key will inserted in Which DB ?

Please clear these doubts ....

Regards,

Dinesh

9790858995

8 Replies

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Nishant Mittal10y ago
I wrote earlier no clues about this.
Dinesh baabu10y ago
?
Dinesh baabu10y ago
I mean Database (DB) ..
Nishant Mittal10y ago
Seems Yes
Dinesh baabu10y ago
And what is the difference between CR_archievw and CR_error ?
Dinesh baabu10y ago
for 4 th question ,For example , My employee ID 32564 like this , if I change the value as 32566 , so this value is inserted in CR_database right , its not insertd to CR_archieve and CR_error
Rahul Chavan10y ago
1. How can I find this is primary key ?
If you open the SQL Managment studio and expand the table , Column will show primary key.
-or-
Try inserting Null value in column
-or-
Use below query
SELECT KU.table_name as tablename,column_name as primarykeycolumn
FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS AS TC
INNER JOIN
INFORMATION_SCHEMA.KEY_COLUMN_USAGE AS KU
ON TC.CONSTRAINT_TYPE = 'PRIMARY KEY' AND
TC.CONSTRAINT_NAME = KU.CONSTRAINT_NAME
and ku.table_name='yourTableName'
ORDER BY KU.TABLE_NAME, KU.ORDINAL_POSITION;

2. Is it possible to get NULL value in primary ? why ?
No Primary can not be Null in SQL Server.
Consider an example, You have student table. each student will be identified uniquely by Roll Number(Primary key). With "Null" Roll number, you will not be able to uniquely identify the student.
Primary key are referenced in other table as Foreign key and it can not be null. It is used in Join, can you create condition Payroll.EmployeeId=Employee.EmployeeId (NULL).

4. Primary Key will inserted in Which DB ?
Primary key will be inserted in same table.
Nishant Mittal10y ago
Hi Dinesh,

1)Primary Key will have unique records so you can find one column or cobination of columns to get the Required out put.
2) Nopes u cant , its a rule.In unique key u can have null values.
3) Dont know
4) Question is not clear.In which db means??