ethyl's 2015-12-03 15:18
Noramlization a techique for producint a set of relations with desirable properties given the data requirements
Referential integrity rule If a relation has a foreign key it must match a candidate key or be null
Entitry integrity rule No part of the primary key can be null
1NF no repeating groups
2NF all non-key fields are dependent on the entire primary key
3NF all non-key fields are NOT dependent on another non-key field.
Relation a table with columns and rows
Html Lists can hace nested items looking like <li> </li>
A triangle Indicates super type/sub type (ISA)
Html Horizontal line <hr>
Weak Entity Indicated by nested rectangles.
Html is not case senstive HTML IS NOT CASE SENSTIVE
Html Empty element An one sided tag like a line break.
Html tag Used to mark elements
Start and end of html <html></html>
H1~H6 Six heading elements, h6 is the smallest
<tr> A table row. Per row nested in <table>
<td> <th> Table detail/header, nested with in <tr>
field A control element where the user can enter information
field value The information user entered
<label for="id"> Labels added to fields
<option value="1">One</option> nested with in <select name="mydropdown">
define("myConst", 4096) This is how to define a const in php.
Differences between include() and require() Require stops immediately on error. Include keeps going.
Blind SQL injections Results is not visible to the attacker
How to minize SQL injects Use php pdo and validate input
Transactions are required to have what properies? ACID
Atomicity A transaction is executed either completely or not at all..
Consistency a transaction operating on a consistent database is guaranteed to leave it in a consistent state. This means all constraints will be satisfied after the transaction or else the transaction will be aborted
Isolation a transaction will execute as if it were executing alone even in the presence of simultaneously executing transactions
Durability updates made by a successful transaction will be durable (persistent) and permanently reflected in the database. They are first recorded in the log and then propagated to the database. Upon system recovery, the log is checked and if there are changes that need to be reflected in the database they are made
How to solve conflict between transactions Locks
Atomicity - S a transaction is a logical unit of work that should be completed entirely or not at all
Consistency - S the database will be consistent with it's own rules when completed
Isolation - S no other users see any parts of the transaction until it is completed
Durability - S all the changes made during the transaction are permanent
Stored Procedure Transactions uses this to catch errors
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