Antonio Lemus watch Ideocracy
Week 10

-Where is null..
-‘M%’ starts with M
-‘%O’ ends in O
-Order by A-Z - ASC Z-A – DESC
-Brackets indicate inside is the same thing (first name) = firstname
-*(Star) - give me everything from
-‘’ (singlequote) - forces whatever is in between to be a string
-SQL server authentication–
-Windows server authentication– trusts
-ETL – Extract Transform Load
-Like – equivalent to equal sign
-Distinct unique rows
-Data Definitional language or DDL is the portion of sequel that is used to create or alter tables, database objects
- How do you create a table – new table--create table
- In which situation should you not allow nulls – required data or business rules require it…?
-If you want to change a value/ foreign key value use – key word ‘update’
-If you want to delete a record/table/value – hit key word ‘delete’
-Referential integrity – when a primary key refers to a foreign key or vice versa/ all references are there.
Do not have referential integrity: Foreign key with no primary key
Do not have referential integrity: Primary key with no foreign key
Does have referential integrity: Foreign key with primary key
Does have referential integrity: Primary key with foreign key
-Absence of a value - null
-varchar or invarchar – strings, names, unit size, quantity
Bit – yes or no
- Natural key – helps protect your identity
- Composite key - has to have two or more columns that make it unique
-unicode refers to an expanded set that has Latin codes a- has a code 1- has a code
-Every action that takes place in a database is called a database transaction
-Physical design – the actual database itself
-1st normal form described best as removing redundancies and anomalies and repeating rules
-2nd normal form the removal of functional dependencies
-update anomaly accurse when you have to edit more than