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12 Cards in this Set
- Front
- Back
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Why PL/SQL? |
Pure SQL may have poor performance. With embedded SQL, each statement is individually sent over the network to be executed on the server. PL/SQL blocks can be sent over. PL/SQL procedures and functions are stored in a parsed and compiled form on the DB server so parsing overhead and network traffic are reduced. |
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What additional functionality is there with PL/SQL? |
Loops, arrays/collections, functions, variables, exception handling, code blocks. |
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What does it mean when DBMSs are 'value-based'? |
Relationships between and attributes of real-life entities are represented by storage of values in table rows. |
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What is an object DBMS? (3) |
- Supports complex object structures e.g. collections - Encapsulates objects by providing procedures to indirectly access and manipulate the internal data representation - Support classes and inheritance |
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What is a key-value store? |
Storage of values in the form of bytes, retrieval by keys. |
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What is a document store? |
Like key-value but the values are actual documents with a structure that may be referenced by the API. MongoDB |
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What is a graph store? |
Information is represented by nodes and edges with properties. |
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What are the advantages of NoSQL databases? |
- Scalability and extensibility (across servers rather than all on one server that needs to be big enough) - Flexibility |
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What are the disadvantages of NoSQL databases? |
- Lack of extensive concurrency control and recovery capabilities - Lack of ACID compliance |
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What is a column store? |
Columns are stored conceptually as a vector of elements consisting of an ID for a row with the encoded values. |
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Advantages of a column store? |
Enables compression, efficient parallel execution using pipelining techniques. |
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Advantages of a document store? |
Flexibility, as there are no fixed schemas. For example in MongoDB all documents are in a JSON-ish format - fields can be added or deleted, and can be different across the collection. |
