Best Mainframe IBM DB2 Interview Questions and Answers: Top Mainframe IBM DB2 Interview Questions and Answers

1. What are foreign keys?
These are attributes of one table too own matching price level in a chief key in a different table, permitting for relationships between tables.

2. Describe the components of the SELECT query syntax
SELECT cog FROM table WHERE conditional statement .

3. Explain the use of the WHERE clause
WHERE is depleted in on a relational statement to isolate the object factor or row.

4. What techniques are exhausted to retrieve information from what i read in a large amount of as opposed to one table in a single SQL Statements?
Joins, unions and nested selects are expended to retrieve data

5. What do the initials DDL and DML stand for and how is the meaning?
DDL is info definition slang and DML is info manipulation gobbledygook DDL statements are CREATE, ALTER, TRUNCATE DML statements are SELECT, INSERT, DELETE and UPDATE .

6. What is a view? Why use it?
A view is a virtual table drew up up of information from what i read in base tables and further views, but not stored separately.

7. Explain an outer join
An outer join includes rows of tables when there are no matching market value in the Tables.

8. What is a sub select? Is it several based on what i read in a nested select?
Sub some is a selected that drives in conjunction provided an additional specific A nested chosen is a type of Sub Select at which the inner pick passes to the at which standards for the outer select.

9. What is the change between committe by and condition by?
Group by controls the presentation of the rows, form by controls the presentation of the columns for the consequences of the SELECT statement .

10. Explain the EXPLAIN statement
The explain statement gives data just about the optimizer's selection of entrance way of the SQL.

11. What is Table Space?
Tables are stored in Table Space (hence the name)! There are 3 sorts of Table Space simple, segmented and partitioned

12. What is a cursor and how is its function?
An embedded Sql statement may come up with a lot of rows additonally the programming blabber can merely entrance one row at a opportunity The programming device labeled a cursor controls the position of the row .

13. What is referential integrity?
Referential integrity refers to the consistency who are required to be maintained between number one and distant keys, ie most every out of country key quality ought to experience a corresponding number one key value.

14.Usually, that is a larger amount of significant for DB2 technique performance - CPU processing or I/O access?

I/O operations are mostly many grim for DB2 performance (or any a good deal more database for the current matter)

15. Is there any advantage to De normalizing DB2 tables?
De-normalizing DB2 tables goes down the would like for processing intensive relational joins and decreases the sum of distant keys.

16. What is the database descriptor ?
The database descriptor, DBD is the DB2 ingredient this limits entrance to the database whenever objects are created, revised or dropped.

17. What is lock contention?
To keep up the integrity of DB2 objects the DBD gives entrance to simply on object at a opportunity Lock contention occurs if a good amount of objects are monumental by vying software manages simultaneously.

18. What is SPUFI?
SPUFI stands for SQL processing making use of File key in It is the DB2 interactive menu-driven program expended by developers to generate database objects

19. What is the significance of DB2 cost free space and how parameters control it?

The two parameters exhausted in the CREATE statement are the PCTFREE that specifies the fee of cost free space for every web page and FREEPAGE that spells the level of webpages to be loaded provided information between every cost free web page Free space provides room for the insertion of new rows

20. What is a NULL value? What are the experts and cons of making the most of NULLS?
A NULL values takes up one byte of storage and signals the a rate is not new as opposed to a space or zero market prices It's the DB2 equivalent of TBD on an organizational chart and often right portrays a economy well being Unfortunately, it requires supplementary coding for an tool bill to solve the current situation.

21. What is a synonym? How is it used?
A synonym is expended to reference a table or view by a new and cr The supplementary and cr can subsequently be written in the program code pointing to test tables in the development evolution and to creation entities when the code is migrated The synonym is connected to the AUTHID the came up with it

22. What is an alias and how performs it fluctuate based on a synonym?
An alias is an substitute to a synonym, programmed for a distributed surroundings to avert suffering to use the location qualifier of a table or view The alias is not fallen when the table is lowered

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