SQL has the following types of joins, all of which come straight from set theory: Inner join. Cross Join. INNER JOIN. In MySQL, JOIN, CROSS JOIN, and INNER JOIN are syntactic equivalents (they can replace each other). In MySQL, the CROSS JOIN produced a result set which is the product of rows of two associated tables when no WHERE clause is used with CROSS JOIN. 在本教程中，您将了解mysql cross join子句以及如何应用它来解决一些有趣的数据问题。. Suppose you join two tables using the CROSS JOIN clause. The SQL CROSS JOIN produces a result set which is the number of rows in the first table multiplied by the number of rows in the second table if no WHERE clause is used along with CROSS JOIN.This kind of result is called as Cartesian Product. cross join子句从连接的表返回行的笛卡儿乘积。. What is Cross Join in SQL? Introduction to MySQL CROSS JOIN clause. From A inner join B is the equivalent of A ∩ B, providing the set of elements common to both sets.

INNER JOIN is used with an ON clause, CROSS JOIN is used otherwise.

Left outer join. Introduction to SQL CROSS JOIN clause. In Math, a Cartesian product is a mathematical operation that returns a product set of multiple sets. MySQL JOINS Tutorial: INNER, OUTER, LEFT, RIGHT, CROSS Types of joins. A cross join is a join operation that produces the Cartesian product of two or more tables. The inner JOIN is used to return rows from both tables that satisfy the given condition. In standard SQL, they are not equivalent. If WHERE clause is used with CROSS JOIN, it functions like an INNER JOIN. In this join, the result set appeared by multiplying each row of the first table with all rows in the second table if no condition introduced with CROSS JOIN. The CROSS JOIN clause returns the Cartesian product of rows from the joined tables. From A left outer join B is the equivalent of (A − B) ∪ (A ∩ B). mysql cross join子句简介. 假设使用cross join连接两个表。结果集将包括两个表中的所有行，其中结果集中的每一行都是第一个表中的行与第二个表中的行的组合。 MySQL supports the following types of joins: Inner join Left join Right join Cross join The result set will include all rows from both tables, where each row is the combination of the row in the first table with the row in the second table. In general, parentheses can be ignored in join expressions containing only inner join …