DB2 Interview Questions - Part 1
Download as PPT, PDF3 likes2,449 views
The document provides a collection of DB2 interview questions and answers, covering topics such as SQL operations (like UNION, WHERE clauses, and wildcard characters), data retrieval, and database utilities like RUNSTATS and REORG. It also discusses COBOL definitions related to DB2 data types and the use of cursors in COBOL programs. Additionally, the document includes contact information for further inquiries.
DB2 Interview Questions - Part 1
- 1. 由 NordriDesign™ 提供 www.nordridesign.com www.rekruitin.com DB2 Interview Questions Part - 1
- 2. Page 2 LOGO 1. What is UNION, UNION ALL? UNION: eliminates duplicates, UNION ALL: retains duplicates . Both these are used to combine the results of different SELECT statements. Suppose I have five SQL SELECT statements connected by UNION/UNION ALL, how many times should I specify UNION to eliminate the duplicate rows? 2. What is the restriction on using UNION in embedded SQL? It has to be in a CURSOR.
- 3. Page 3 LOGO 3. In the WHERE clause what is BETWEEN and IN? BETWEEN supplies a range of values while IN supplies a list of values. 4. What is 'LIKE' used for in WHERE clause? What are the wildcard characters? LIKE is used for partial string matches. ‘%’ (for a string of any character ) and ‘_’ (for any single character ) are the two wild card characters. 6. Is BETWEEN inclusive of the range values specified? Yes.
- 4. Page 4 LOGO 7. Consider the employee table with column PROJECT nullable. How can you get a list of employees who are not assigned to any project? SELECT EMPNO FROM EMP WHERE PROJECT IS NULL; 8. What is the result of this query if no rows are selected? SELECT SUM(SALARY) FROM EMP WHERE QUAL=‘MSC’; NULL 9. How do you retrieve the data from a nullable column? Use null indicators. Syntax ... INTO :HOSTVAR:NULLIND
- 5. Page 5 LOGO 10. How do you insert a record with a nullable column? To insert a NULL, move -1 to the null indicator To insert a valid value, move 0 to the null indicator 11. What is RUNSTATS? A DB2 utility used to collect statistics about the data values in tables which can be used by the optimizer to decide the access path. It also collects statistics used for space management. These statistics are stored in DB2 catalog tables.
- 6. Page 6 LOGO 12. Give some example of statistics collected during RUNSTATS? # of rows in the table Percent of rows in clustering sequence # of distinct values of indexed column # of rows moved to a nearby/farway page due to row length increase 13. What is REORG? When is it used? REORG reorganizes data on physical storage to reclutser rows, positioning oveflowed rows in their proper sequence, to reclaim space, to restore free space. It is used after heavy updates, inserts and delete activity and after segments of a segmented tablespace have become fragemented.
- 7. Page 7 LOGO 26. Give the COBOL definition of a VARCHAR field. A VARCHAR column REMARKS would be defined as follows: 10 REMARKS. 49 REMARKS-LEN PIC S9(4) USAGE COMP. 49 REMARKS-TEXT PIC X(1920). 27. What is the physical storage length of each of the following DB2 data types: DATE, TIME, TIMESTAMP? DATE: 4bytes TIME: 3bytes TIMESTAMP: 10bytes
- 8. Page 8 LOGO 31. What are the contents of a DCLGEN? EXEC SQL DECLARE TABLE statement which gives the layout of the table/view in terms of DB2 datatypes. A host language copy book that gives the host variable definitions for the column names. 32. Is it mandatory to use DCLGEN? If not, why would you use it at all? It is not mandatory to use DCLGEN. Using DCLGEN, helps detect wrongly spelt column names etc. during the pre-compile stage itself ( because of the DECLARE TABLE ). DCLGEN being a tool, would generate accurate host variable definitions for the table reducing chances of error.
- 9. Page 9 LOGO 33. How do you specify and use a cursor in a COBOL program? Use DECLARE CURSOR statement either in working storage or in procedure division(before open cursor), to specify the SELECT statement. Then use OPEN, FETCH rows in a loop and finally CLOSE. 34. What happens when you say OPEN CURSOR? If there is an ORDER BY clause, rows are fetched, sorted and made available for the FETCH statement. Other wise simply the cursor is placed on the first row.
- 10. Page 10 LOGO Contact Us : For more details, Please log on to www.rekruitin.com Customer Care: 8855041500 Career Guidance : 9823205144 Tech Support : 7758806112 Human Resource: 9823204144 You can also Find us on:
- 11. 11