Since you can set any arbitrary attribute value (and yes, that includes values that you define) to a constraint expression or use it in a constraint, there are a lot of possibilities.

由于可以为约束表达式设置任何任意的属性值(包括您自己定义的值)，或者在约束中使用它，因此存在很多可能。

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You can use a simple regular expression to specify that you want to find a line containing one word followed by another.

可以使用简单的正则表达式指定寻找包含某一单词而且后面有另一个单词的行。

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You can use a scalar subquery to select a specific value that will be used in the expression of the WHERE clause.

可以使用标量子查询选择将用于where子句的表达式中的特定值。

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