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Oracle deferrable选项

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2016-06-07 16:57:361178browse

解释一下,即:将约束检验延迟到了执行COMMIT的时候。以下是具体的解释和举例。 定义为可延迟(deferrable)的约束可以指定为:1

解释一下,即:将约束检验延迟到了执行COMMIT的时候。以下是具体的解释和举例。 定义为可延迟(deferrable)的约束可以指定为:

1. initially immediate(初始化立即执行)或

2. initially deferred(初始化延迟执行)。

解释二者的区别。初始化立即执行/延迟执行规定了在默认情况下应该如何执行约束:

初始化立即执行--在每条语句执行结束时检验约束

初始化延迟执行--一直等到事务完成后(或者调用set constraint immediate语句时)才检验约束

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