The SIGNAL statement is used to explicitly raise an error and force the invocation of a handler.

signal语句用于显式地发出一个错误并强制调用处理程序。

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Any valid SQLSTATE value can be used in the SIGNAL statement, including user-defined SQLSTATEs and conditions.

任何有效sqlstate值都可以用于signal语句中，包括用户定义的SQLSTATE和条件。

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The SIGNAL statement rolls back the changes that were attempted by the triggering statement (that is, our update statement).

SIGNAL 语句回滚由触发语句（也就是我们的 update 语句）尝试的更改。

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More broadly, the statement is another signal that the U.S. is entering a Goldilocks scenario.

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The financial markets interpreted his last statement as a clear signal that he's going to raise interest rates at the end of June, and now there's some speculation that he'll keep raising them after that, which is a change of view.

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The statement is the first public signal from the government that it will take concrete steps in response to reports in state-run media, though it was unclear from the report just how it would heighten oversight of the industry.

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