card是指计划中这一步所处理的行数。cost指cbo中这一步所耗费的资源，这个值是相对值。bytes指cbo中这一步所处理所有记录的字节数，是估算出来的一组值。 http://blog.itpub.net/post/385/45197[@more@]
■ Cost The cost assigned to each step of the query plan by the CBO. The CBO works by
generating many different execution paths/plans for the same query and assigns a cost to
each and every one. The query plan with the lowest cost wins. In the full outer join example,
we can see the total cost for this query is 10.
■ Card Card is short for Cardinality. It is the estimated number of rows that will flow out
of a given query plan step. In the full outer join example, we can see the optimizer expects
there to be 327 rows in EMP and 4 rows in DEPT.
■ Bytes The size in bytes of the data the CBO expects each step of the plan to return.
This is dependent on the number of rows (Card) and the estimated width of the rows.
generating many different execution paths/plans for the same query and assigns a cost to
each and every one. The query plan with the lowest cost wins. In the full outer join example,
we can see the total cost for this query is 10.
■ Card Card is short for Cardinality. It is the estimated number of rows that will flow out
of a given query plan step. In the full outer join example, we can see the optimizer expects
there to be 327 rows in EMP and 4 rows in DEPT.
■ Bytes The size in bytes of the data the CBO expects each step of the plan to return.
This is dependent on the number of rows (Card) and the estimated width of the rows.
看来，
card是指计划中这一步所处理的行数。
cost指cbo中这一步所耗费的资源，这个值是相对值。
bytes指cbo中这一步所处理所有记录的字节数，是估算出来的一组值。
来自 “ ITPUB博客 ” ，链接：https://blog.itpub.net/14377/viewspace-925434/ ，如需转载，请注明出处，否则将追究法律责任。
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