In this section, you will find links for videos by Jens Dittrich (Prof. Univ Saarland) describing topics relevant for this course. Some videos will explain topics with a deeper level of detail than we have done in theoretical classes, which is perfect for those of you who want to know more about a subject.Other videos are available at Jens Dittrich's youtube channel (

Storage Hierarchy:

Hard disks, sectors, blocks, etc:

Hard disks, Sequential vs Random Access:


Pulling up and pushing down data, database buffer, blocks, spatial vs temporal locality:

The Data Redundancy Pattern:

Data layout:

Mapping Relations into Pages:

Slotted Pages:

Slotted Pages - Fixed-size versus Variable-size Components:

Finding free space:

Motivation for Index Structures, Selectivities, Scan vs. Index Access on Disk and Main Memory:

Three Reasons for Using B-Tree Indexes, Intuition, Properties, find, ISAM, find_range:

Clustered, Unclustered, Dense, Sparse, Coarse-Granular Index:

Covering and Composite Index, Duplicates, Overflow Pages, Composite Keys:

Bulk-loading B-Trees or other Tree-structured Indexes:

Static Hashing, Array vs Hash, Collisions, Overflow Chains, Rehash:


External Merge Sort:

Applications of Join Algorithms, Nested-Loop Join, Index Nested-Loop Join:

Simple Hash Join:

Sort Merge Join:

Grouping and Aggregation:

Query Planning and Optimization: