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Q:

Why SELECT * is not preferred in embedded SQL programs?

Answer

- If the table structure is changed ( a field is added ), the program will have to be modified.


- Program might retrieve the columns which it might not use, leading on I/O over head.


- The chance of an index only scan is lost.

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Subject: Mainframe Interview

Q:

What is meant by index cardinality?

Answer

The number of distinct values for a column is called index cardinality. DB2's RUNSTATS utility analyzes column value redundancy to determine whether to use a tablespace or index scan to search for data.

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Subject: Mainframe Interview

Q:

How will u send data from a cobol file to db2 table?

Answer

USING HOST VARIABLE we can pass data from COBOL to DB2

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Subject: Mainframe Interview

Q:

What is a DB2 bind?

Answer

A DB2 bind is a process that builds an access path to DB2 tables. 

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Subject: Mainframe Interview

Q:

What is a DB2 plan?

Answer

An application plan or package is generated by the bind to define an access path. 

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Subject: Mainframe Interview

Q:

My SQL statement SELECT AVG(SALARY) FROM EMP yields inaccurate results. Why?

Answer

Because SALARY is not declared to have NULLs and the employees for whom the salary is not known are also counted.


 

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Subject: Mainframe Interview

Q:

File contains 5 records say D,E,F,C,A-I want to copy D and A records only by using file-aid?

Answer

Go to file-aid copy option.Enter the from dataset to be copied and to dataset to which you want to copy.go to options. Enter 0 at Initial records to skip field.Then enter 3 at the no of records to skip field and 1 to no of records to select.press enter and PF3.

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Subject: Mainframe Interview

Q:

What is the self-referencing constraint?

Answer

A31. The self-referencing constraint limits in a single table the changes to a primary key that the related foreign key defines. The foreign key in a self referencing table must specify the DELETE CASCADE rule.

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Subject: Mainframe Interview