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45 Cards in this Set
- Front
- Back
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Relational DataBase |
Contains a collection of separate tables. The concept is to have each table with a single theme |
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Intsert |
Able to insert data or a row of data with out disturbing the table |
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Update |
Changed data where there is no inconsistancy |
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Delete |
Ables to delete data with no consequences in the other tables |
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Insert, Update, delete EX |
Adding professor to an advisor table who is not an adivisor Updating the professors email bc it will be stored just once in the advisor table Deleting s tudents information will not effect the advisor because it will be in another table |
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Problems with Lists |
Inserting, updating, and deleting screw the whole list up. |
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Functions of DBMS |
Create database creat tables create supporting structures read data madify data maintain structures Enforce rules controlly concurrency provide security perform backup and recovery |
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data types |
auto num numeric currency text date |
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Why avoid null values? |
The user does not know what that means |
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3 main rules for normalization |
Get rid of repeating groups Get rid of partial dependencies Get rid of transitive dependencies |
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composite key 8 |
more than 1 field that make up a primary key |
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Surrogate key |
A field related to the field that would be a good name for the primary key |
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cascade delete |
If you delete the primary key in the primary table, it deletes all other foreign keys that corresponds with the primary key |
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Cascade update |
If you update the primary key in the primary table, it updates all other foreign keys that corresponds with the primary key |
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Why normalize |
to reduce and even eliminate data redundancy
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Built in functions |
Max Min Sum Count Add Avg |
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INNER JOIN |
Table1 INNER JOIN (TABLE2 INNER JOIN bridgetable ON bridgeTable.[field] = Table2.[field]) ON Table1.[field] = Table2.[field]; |
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sql how to write LIKE |
'*WORDS*' |
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DISTINCT |
Eliminates key words |
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redundancy |
Unnecessary repeated information |
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concurrency |
2 or more people trying to access the same data at the same time |
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Referential integrity constraints |
A relationship constraint on foreign keys values. It specifies the values of a foreign key must be a proper subset of the values of the primary key |
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database |
Self describing collection of related tables |
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DBMS 8 |
set of programs used to define, administer, and process a database and its applications |
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Metadata |
Data concerning the structure of databases |
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Relational model |
Shows which data is stored in relationships between rows and the values |
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foreign key 8 |
An attribute that is a key of one or more relations |
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NULL value |
Values that can be unknown, not appropriate, or can be blank |
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Primary key |
Key of relation , it is selected |
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when in the where section and want to have a limit to a certain word, what do you put around the word |
single quotes |
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EXAMPLE OF Average if you need the average donation value for adopted animals |
SELECT AVG(DONATION) AS [Average Donation Value] FROM Animal; |
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AS represents |
Name the title whatever is between brackets |
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EXAMPLE of total value of an order number 22 |
SELECT sum(COST) AS [Value] FROM OrderItem WHERE PONumber = 22; |
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EXAMPLE of number of days between when it was ordered and when it was received |
SELECT PONumber, ReveiceDate, OrderDate, (ReceiveDate-OrderDate) AS [Number of days] From MerchandiseOrder; |
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How to write a date |
#1/1/0001# |
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4 concepts and features of a primary key 8 |
cannot have a meaning Cannot change Cannot be null uniquely identifies records |
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What to do when you first start a database? |
Get the data from the user |
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data model |
how data is connected to each other and how they are processed and stored inside the system. |
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ER MODEL |
entity-relationship (ER) diagram, is a graphical representation of entities and their relationships to each other, typically used in computing in regard to the organization of data within databases or information systems. |
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entity |
Restricted to things that can be represented to a single table |
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Strong entity |
does not depend on another entity |
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Weak entity |
dpends on another entity |
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id dependent entity |
Cant exsist without another entity |
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max/min cardinality |
Maximum cardinality is the maximum number of instances of an entity that can participate in an instance of a relationship. Minimum is the least number of instances of an entity that can participate in an instance of a relationship. |
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subtype |
EX ENGINEER IS A SUB TYPE OF EMPLOYEE |
