应用程序可以将某行的当前行修改标记值与上次取回行时保存的行修改标记值进行比较，以判断行是否发生修改。

An application can compare the current row change token value of a row with the row change token value that was stored when the row was last fetched to determine whether the row has changed.

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rake通过读取schema_info表中version列的值，判断当前迁移的编号。

Rake determines the number of the current migration by reading the value of the version column in the schema_info table.

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用窗口实时移动的思想计算当前时刻以前一周波电流方均根值平方作为瞬动脱扣的判断依据。

Using the method of window moving in real time, the root mean square value of current of the last cycle was calculated as the criteria for instantaneous overcurrent protection.

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