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React Easy Theory

Lists and keys in React

React uses keys to identify list items across renders so reconciliation can preserve identity correctly.

  • Keys must be stable and unique within the list
  • Indexes can break identity when order changes
  • Keys affect correctness as well as performance
#keys #lists #react

Lists and keys in React

SQL Easy Theory

Primary key vs foreign key

A primary key uniquely identifies a row in its own table, while a foreign key points to a related row in another table.

  • Primary key is table identity
  • Foreign key creates relationship
  • Helps enforce referential integrity
#keys #schema-design #sql

Primary key vs foreign key