have doubt

Question

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_ARCHIVEAND CR_ERROR ? 4. Primary Key will inserted in Which DB ? Please clear these doubts .... Regards Dinesh 9790858995

Nishant Mittal · Answer

I wrote earlier no clues about this.

Dinesh baabu · Answer

?

Dinesh baabu · Answer

I mean Database (DB) ..

Nishant Mittal · Answer

Seems Yes

Dinesh baabu · Answer

And what is the difference between CR_archievw and CR_error ?

Dinesh baabu · Answer

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 Chavan · Answer

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 tablenamecolumn_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 Mittal · Answer

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??