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NORMALISATION?, Constraints, 3NF, 2NF, 1NF, OVERVIEW, Relationships -…
NORMALISATION?
1, 2 + 3
2NF. BREAKDOWN
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Cust.Address, is required on orders, shipping, invoices and payments.
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Constraints
Primary key
attribute or set of attributes, uniquely identify each row
Foreign key
matching column or combo of columns, establish link between tables
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Trigger
complex T-SQL statements, provide data integrity when table data is modified
Composite key
index or constraint, using more than one column to create a unique value for each row in a table - combine any two constraints
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3NF
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REMOVE DUPLICATES
No duplicates, Redundant data is removed
DEFINE RELATIONSHIPS
Tables must have a matching key column - PK match FK - 1:N, N:N
ELIMINATE FIELDS
Check for transitive dependencies, NOT dependent on the key (transfer to junction table)
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OVERVIEW
1NF. - Remove group repeats, no duplicate information
2NF. - Breakdown, logical grouping into themed, single topic tables, that are related.
3NF. - Eliminate non-key dependent data, create a junction or relation table
Clean dataset - remove all duplicates
Logical Grouping - organise data into relating tables.
Eliminate non-related data.
Enforce standards - integrity of data.
Protect & Secure data. User Access with Permissions
Relationships
1:1 - one to one - PK matches Pk in both tables
1:N - one to many - PK matches to PK in many tables tables
N:N - many to many - many PK match many FK in many tables