Posted On: Feb 22, 2018
Nested loop- A nested loop is a loop within a loop. It is an inner loop within an outer body that allows fewer entries. Individual entries in nested loop is processed individually in the inner loop. Example-
.Select col.*, col2.* from coll, col2 where coll.coll=col2.col2; The nested way works in following format- For i in (select*from coll) loop For j in (select*from col2 where col2 = i.coll) loop Results are displayed End of the loop; End of the loop;
For nested loop, first outer (driving) table is identified. Then inner tavle is assigned to the outer table and every row in inner column is accessible from every row of outer table. Nested loop is executed from hash join, inner loop and then outer loop.
Hash join- it is divided into-
It is considered a better option as compared with nested loop when data volume is big. The full operation of hash join can be classified as-
Sort join operation-
Get first row R1 from input1 Get first row R2 from input2 Merge join operation- 'while' command is not used at loop's end. If R1 joins with R2 Next row is got R2 from the input2 Return (R1,R2) else if R1 ,style="". Next row is got from R1 from input1 else next row is got from R2 from input 2 end of the loop.
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There are various kinds of interactions supported by DBMS like- Data definition Update Retrieval Administration..