Refresher/SQL/Basic Concepts


Basic Concepts    
 Constraint: an input filter
 Denormalizing: performance improvement through reduction in number of joins needed for data processing
 Group by and order by clauses: expensive due to creation of temporary tables
 Indexes' tradeoffs: faster retrieval, slower updates
 Join: a logical connection between two tables
 Normalizing: eliminating redundant information and making it easier for future updates
 Primary key: a combination of columns which uniquely specify a row
 Trigger: the code automatically executed in response to certain table events
 Where vs having: where is a restriction and having is a filter
 Wildcard: % using LIKE