One post tagged with "连接消除"

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Definition​

Join Elimination is a rewriting optimization in SQL that simplifies queries and improves query performance by removing joins from the query without affecting the final result. Typically, this optimization is used when a query contains a primary-foreign key join and only references the primary key columns of the main table.

Consider the following example:

select o.* from orders o inner join customer c on c.c_custkey=o.o_custkey

The orders table is joined with the customer table, and c_custkey is the primary key of the customer table. In this case, the customer table can be eliminated, and the rewritten SQL would be:

select * from orders where o_custkey