Help
Options
Didn't know it?
click below
click below
Knew it?
click below
click below
Don't Know
Remaining cards (0)
Know
retry
shuffle
restart
0:00
Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.
Normal Size Small Size show me how
Normal Size Small Size show me how
DatabaseEmergency
database systems
| Question | Answer |
|---|---|
| 3 kinds of schema, what are they? | External, internal, conceptual |
| describe external schema | view closest to users. User view; shows what a particular user group is interested in and hides the rest of the DB from them |
| describe conceptual level | describes the database for a community of users; hides details of physical storage, contains constraints, data types, relationships, user operations and entities; created by the DBA |
| what's data independence | Logical independence, you can change up the conceptual schema without having to change the external schema or application programs |
| what's physical independence | you can change the physical (internal level) without changing the conceptual schema |
| candidate key | If you have 2 keys, choose one as the primary and the other is the candidate key which could potentially switch roles with the original primary key |
| primary key | unique & non, redundant, that distinguishes tuple from table (can have single or multi variable attributes) |
| foreign key | not a key but an attribute so a connection can be made |
| Entity Integrity constraint | no primary key value can be NULL |
| referential integrity constraint | maintains consistency between 2 tuples |
| 3 operations on a DB | Insert Delete Update |
| Insert's constraint violations | Domain integrity Key integrity violation Entity integrity violation Referential integrity violation |
| Domain integrity violation | wrong data type or not in this defined domain |
| key integrity violation | duplicate key in this table (two same SSN's) |
| Entity integrity violation | Primary key has a null value |
| referential integrity violation | foreign key of new entity doesn't have a primary key to reference |
| Delete violates only this integrity | referential integrity (you got rid of a tuple that had a primary key someone was looking at) |
| what is done when delete violates referential integrity? | 1 Reject the deletion 2 cascade 3 set the refernced tuple to NULL or default |
| Update's violations are... | the exact same as INSERT's |
| define a view | virtual/derived/not-real table that can only be built on the base table |
| Technical factor to consider in choosing a DB | 1 DDl's and DML's must be compared 2 Storage of the system must be compared 3 Access path to know how the data will be retrieved 4 user interface 5 Backup & recovery procedure 6 Security/Integrity 7 Built-in-functions to make programming easier |
| define normalization | process of analyzing relation schema to get 1 minimized redundancy 2 minimize the insertion, deletion and update anomalies |
| 1st normal form | the only attribute values are atomic (pretty much means each cell only has a single value & no duplicate rows) |
| 2nd normal form | everything that's in the relational table is completely dependent on the primary key of that table |
| 3rd normal form | 2nd normal form but no attributes are transitively dependent on a relational primary key from the same table (see p524 in textbook if this is confusing) |
| 3 ways to store on a disk | sequential organization direct organization Indexed sequential |
| Sequential Organization | stored one after the other with sequential access |
| direct organization | the disk address & data ID have direct access |
| indexed sequential | looks at groups of addresses one after another |
| 3 things to know about physical design | 1 file organization (see ways to store on disk) 2 choices to improve response time 3 factors that influence physical DB design |
| Things to improve retrieval | 1 Response time 2 throughput 3 space utilization |
| Factors that influence database designs | 1 Queries/transactions-what kind of queries 2 Analyzing the expected freq of the queries-how often is a query used 3 Analyzing the time constraint 4 Analyzing the expected frequency of updated operations 5 Analyzing the uniqueness of analyzed attribut |
| Describe internal schema | Describes the physical storage structure of the DB which includes data storage and access paths |
Created by:
truPrince
Popular Computers sets