Database-Management-System
August 29, 2024Database-Management-System
August 29, 2024Database-Management-System
| Question 719 |
State whether TRUE or FALSE
- (i) Secondary index cannot be defined on key attribute values
(ii) In B+ tree indexing the non-leaf nodes contain the actual data pointers
| (i)-False, (ii)-True | |
| (i)-True, (ii)-True
| |
| (i)-False, (ii)-False
| |
| (i)-True, (ii)-False |
Question 719 Explanation:
→ Secondary Index does not have any impact on how the rows are actually organized in data blocks. They can be in any order. The only ordering is w.r.t the index key in index blocks.
→ Indexing can be of the following types −
1. Primary Index − Primary index is defined on an ordered data file. The data file is ordered on a key field. The key field is generally the primary key of the relation.
2. Secondary Index − Secondary index may be generated from a field which is a candidate key and has a unique value in every record, or a non-key with duplicate values.
3. Clustering Index − Clustering index is defined on an ordered data file. The data file is ordered on a non-key field.
→ B+ tree
The structure of leaf nodes of a B+ tree is quite different from the structure of internal nodes of the B+ tree. Since data pointers are present only at the leaf nodes, the leaf nodes must necessarily store all the key values along with their corresponding data pointers to the disk file block, in order to access them. Moreover, the leaf nodes are linked to provide ordered access to the records.
→ Indexing can be of the following types −
1. Primary Index − Primary index is defined on an ordered data file. The data file is ordered on a key field. The key field is generally the primary key of the relation.
2. Secondary Index − Secondary index may be generated from a field which is a candidate key and has a unique value in every record, or a non-key with duplicate values.
3. Clustering Index − Clustering index is defined on an ordered data file. The data file is ordered on a non-key field.
→ B+ tree
The structure of leaf nodes of a B+ tree is quite different from the structure of internal nodes of the B+ tree. Since data pointers are present only at the leaf nodes, the leaf nodes must necessarily store all the key values along with their corresponding data pointers to the disk file block, in order to access them. Moreover, the leaf nodes are linked to provide ordered access to the records.
Correct Answer: C
Question 719 Explanation:
→ Secondary Index does not have any impact on how the rows are actually organized in data blocks. They can be in any order. The only ordering is w.r.t the index key in index blocks.
→ Indexing can be of the following types −
1. Primary Index − Primary index is defined on an ordered data file. The data file is ordered on a key field. The key field is generally the primary key of the relation.
2. Secondary Index − Secondary index may be generated from a field which is a candidate key and has a unique value in every record, or a non-key with duplicate values.
3. Clustering Index − Clustering index is defined on an ordered data file. The data file is ordered on a non-key field.
→ B+ tree
The structure of leaf nodes of a B+ tree is quite different from the structure of internal nodes of the B+ tree. Since data pointers are present only at the leaf nodes, the leaf nodes must necessarily store all the key values along with their corresponding data pointers to the disk file block, in order to access them. Moreover, the leaf nodes are linked to provide ordered access to the records.
→ Indexing can be of the following types −
1. Primary Index − Primary index is defined on an ordered data file. The data file is ordered on a key field. The key field is generally the primary key of the relation.
2. Secondary Index − Secondary index may be generated from a field which is a candidate key and has a unique value in every record, or a non-key with duplicate values.
3. Clustering Index − Clustering index is defined on an ordered data file. The data file is ordered on a non-key field.
→ B+ tree
The structure of leaf nodes of a B+ tree is quite different from the structure of internal nodes of the B+ tree. Since data pointers are present only at the leaf nodes, the leaf nodes must necessarily store all the key values along with their corresponding data pointers to the disk file block, in order to access them. Moreover, the leaf nodes are linked to provide ordered access to the records.
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