27 real Indexing Internals questions from the SQL bank, as asked in Indian campus drives and tech interviews. Every question has a verified answer and an AI-tutor explanation on placd — free to start.
1. What is B-tree index?
Mid
A.the situation where adding indexes slows inserts, updates, and deletes because every modification must also maintain each index structure
B.the ratio of distinct values to total rows for a column, where a high value makes the index more effective at filtering
C.an index that includes every column a query needs so the engine answers it from the index alone without touching the table heap
D.the default balanced-tree structure that keeps keys sorted and supports equality and range lookups in logarithmic time
A.B-tree index — the situation where adding indexes slows inserts, updates, and deletes because every modification must also maintain each index structure
B.B-tree index — the default balanced-tree structure that keeps keys sorted and supports equality and range lookups in logarithmic time
C.B-tree index — an index whose key order defines the physical storage order of the table rows, so there can be only one per table
D.B-tree index — a separate structure that stores keys plus pointers to the rows, leaving the table data physically unordered and allowing many per table
5. Which term means: "a structure that maps keys to buckets via a hash function, giving fast equality lookups but no support for range or ordered scans"?
A.Hash index — an index built over only the subset of rows matching a WHERE condition, keeping it smaller and cheaper for queries that share that filter
B.Hash index — the situation where adding indexes slows inserts, updates, and deletes because every modification must also maintain each index structure
C.Hash index — the principle that a composite index can be used only for a query that filters on a contiguous prefix of its columns starting from the first one
D.Hash index — a structure that maps keys to buckets via a hash function, giving fast equality lookups but no support for range or ordered scans
A.Clustered index — a structure that maps keys to buckets via a hash function, giving fast equality lookups but no support for range or ordered scans
B.Clustered index — an index built over only the subset of rows matching a WHERE condition, keeping it smaller and cheaper for queries that share that filter
C.Clustered index — an index whose key order defines the physical storage order of the table rows, so there can be only one per table
D.Clustered index — the ratio of distinct values to total rows for a column, where a high value makes the index more effective at filtering
11. Which term means: "a separate structure that stores keys plus pointers to the rows, leaving the table data physically unordered and allowing many per table"?
A.Non-clustered index — a separate structure that stores keys plus pointers to the rows, leaving the table data physically unordered and allowing many per table
B.Non-clustered index — the situation where adding indexes slows inserts, updates, and deletes because every modification must also maintain each index structure
C.Non-clustered index — the default balanced-tree structure that keeps keys sorted and supports equality and range lookups in logarithmic time
D.Non-clustered index — a structure that maps keys to buckets via a hash function, giving fast equality lookups but no support for range or ordered scans
14. Which term means: "an index that includes every column a query needs so the engine answers it from the index alone without touching the table heap"?
A.Covering index — the default balanced-tree structure that keeps keys sorted and supports equality and range lookups in logarithmic time
B.Covering index — a separate structure that stores keys plus pointers to the rows, leaving the table data physically unordered and allowing many per table
C.Covering index — an index that includes every column a query needs so the engine answers it from the index alone without touching the table heap
D.Covering index — a structure that maps keys to buckets via a hash function, giving fast equality lookups but no support for range or ordered scans
A.Index selectivity — the principle that a composite index can be used only for a query that filters on a contiguous prefix of its columns starting from the first one
B.Index selectivity — an index that includes every column a query needs so the engine answers it from the index alone without touching the table heap
C.Index selectivity — the situation where adding indexes slows inserts, updates, and deletes because every modification must also maintain each index structure
D.Index selectivity — the ratio of distinct values to total rows for a column, where a high value makes the index more effective at filtering
20. Which term means: "the principle that a composite index can be used only for a query that filters on a contiguous prefix of its columns starting from the first one"?
A.Leftmost-prefix rule — a structure that maps keys to buckets via a hash function, giving fast equality lookups but no support for range or ordered scans
B.Leftmost-prefix rule — the default balanced-tree structure that keeps keys sorted and supports equality and range lookups in logarithmic time
C.Leftmost-prefix rule — a separate structure that stores keys plus pointers to the rows, leaving the table data physically unordered and allowing many per table
D.Leftmost-prefix rule — the principle that a composite index can be used only for a query that filters on a contiguous prefix of its columns starting from the first one
23. Which term means: "the situation where adding indexes slows inserts, updates, and deletes because every modification must also maintain each index structure"?
A.Write-heavy index penalty — the default balanced-tree structure that keeps keys sorted and supports equality and range lookups in logarithmic time
B.Write-heavy index penalty — an index whose key order defines the physical storage order of the table rows, so there can be only one per table
C.Write-heavy index penalty — the situation where adding indexes slows inserts, updates, and deletes because every modification must also maintain each index structure
D.Write-heavy index penalty — a structure that maps keys to buckets via a hash function, giving fast equality lookups but no support for range or ordered scans
26. Which term means: "an index built over only the subset of rows matching a WHERE condition, keeping it smaller and cheaper for queries that share that filter"?
A.Partial index — the default balanced-tree structure that keeps keys sorted and supports equality and range lookups in logarithmic time
B.Partial index — an index built over only the subset of rows matching a WHERE condition, keeping it smaller and cheaper for queries that share that filter
C.Partial index — a structure that maps keys to buckets via a hash function, giving fast equality lookups but no support for range or ordered scans
D.Partial index — the ratio of distinct values to total rows for a column, where a high value makes the index more effective at filtering
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