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Q: What is ROW_NUMBER()?
Answer:
ROW_NUMBER() assigns sequential numbers. ROW_NUMBER() OVER (ORDER BY col). Numbers restart per PARTITION BY group. Use for paging, deduplication (keep first), ranking. Result is numeric.
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Q: What is OVERFLOW condition?
Answer:
OVERFLOW when output exceeds page. During SEND with paging. Handle to manage paging. RESP check. Terminal specific limits. May need to restructure output.
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Q: What is FETCH FIRST?
Answer:
FETCH FIRST n ROWS ONLY limits result set. SELECT * FROM t ORDER BY col FETCH FIRST 10 ROWS ONLY. Optimizes query - doesn't retrieve all. OFFSET for paging. WITH TIES includes equal values.
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Q: What is PAGING option?
Answer:
PAGING breaks large output. EXEC CICS SEND MAP PAGING. User navigates pages. Autopaging available. Terminal paging commands. For long reports on screen.
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Q: How to do paging with DB2?
Answer:
Use FETCH FIRST n ROWS ONLY with OFFSET or ROW_NUMBER(). Modern: SELECT * FROM (SELECT ROW_NUMBER() OVER(ORDER BY col) AS rn, t.* FROM table t) WHERE rn BETWEEN start AND end. Or cursor with FETCH FIRST.