What is the difference between a primary key and a foreign key in a database?
A primary key is a unique identifier for each record in a database table, ensuring no duplicates. A foreign key is a column that links to the primary key of another table, creating a relationship between them.
Explain the concept of normalization in databases.
Normalization is the process of organizing data in a database to reduce redundancy and improve data integrity by dividing a database into tables and defining relationships between them.
How would you optimize a SQL query that joins multiple tables and is performing slowly?
Optimization can involve indexing key columns, reducing the number of joins, using appropriate WHERE clauses, analyzing query execution plans, and considering partitioning or denormalization in some cases.