所有新的星型连接指令都是查询层次的指令，会影响查询的执行。

All the new star join directives are query level directives that affect the execution of a query.

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如果查询中使用星型连接指令，指令会将会话环境设置覆盖。

If star join directives are used in a query, directives override session environment setting.

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STAR_JOIN—STAR_JOIN指令指示优化器尽可能地选择星型连接计划。

STAR_JOIN - the STAR_JOIN directive instructs the optimizer to favor a star join plan whenever possible.

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