Section 3.9 - CS 2550: Introduction to Database Design and SQL | zyBooks

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• Codd's operations, called relational algebra, have since been refined and are the theoretical foundation of SQL.

• The select operation selects table rows based on a logical expression.

• is equivalent to SELECT * FROM Table WHERE expression.

• The project operation selects table columns.

• is equivalent to SELECT Column1, Column2, ... FROM Table.

• The product operation combines two tables into one result.

• SELECT * FROM Table1 CROSS JOIN Table2.

• The join operation, denoted with a "bowtie" symbol,

• The join operation is equivalent to SELECT * FROM Table1 INNER JOIN Table2 ON expression.

• the join operation is sometimes called a theta join.

• Compatible tables have the same number of columns with the same data types.

• Union, intersect, and difference operate on compatible tables and, collectively, are called set operations

• The union operation combines all rows of two compatible tables into a single table.

• SELECT * FROM Table1 UNION SELECT * FROM Table2.

• Intersect operates on two compatible tables and returns only rows that appear in both tables.

• SELECT * FROM Table1 INTERSECT SELECT * FROM Table2

• The difference operation removes from a table all rows that appear in a second compatible table.

• SELECT * FROM Table1 MINUS SELECT * FROM Table2

• The rename operation specifies new table and column names.

• The aggregate operation applies aggregate functions like SUM(), AVG(), MIN(), and MAX().