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Normalization

Database normalization is the process of decomposing tables to eliminate redundancy and update anomalies, with normal forms from 1NF to BCNF/5NF growing stricter.

Purpose

To eliminate data redundancy and update anomalies (insert/delete/modify), guaranteeing data integrity.

Mechanism

1NF: atomic values. 2NF: eliminate partial dependencies (non-prime attributes fully depend on the key). 3NF: eliminate transitive dependencies. BCNF: every determinant is a candidate key. Normalization reduces redundancy but adds JOINs; balance against denormalization.

Use cases

  • Relational database design
  • Eliminating data redundancy
  • Data integrity assurance
  • Teaching and modeling

Examples

  • Input 
    Split an orders table into orders + customers + products
    Output 
    3NF eliminates redundancy

    Table decomposition

Common errors

Over-normalization leads to excessive JOINs in queries
Denormalize moderately for read-heavy scenarios

Related terms

Index
An index is an auxiliary data structure (e.g., B+ tree, hash) maintained to speed up queries, trading space for time at the cost of write overhead.
GLOSSARY
JOIN
JOIN is the SQL operation combining rows of multiple tables by a join condition; types include inner, left/right/full outer, and cross joins.
GLOSSARY
Primary Key
A primary key is the column or column combination that uniquely identifies each row in a table — non-null and unique; the row identity.
GLOSSARY
Foreign Key
A foreign key is a column referencing the primary key of another table, establishing referential integrity between tables and preventing orphaned references.
GLOSSARY

Related tools

SQL Formatter
Beautify or minify SQL queries online. Uppercase keywords, indent clauses, or compress to a single line. Free, private, and 100% client-side.
TOOL

References