When the if clause has more than one condition, you can choose to have it evaluate to true when any of the conditions are true or when all of the conditions are true.
当 if 子句有多个条件时，您可以选择让它在任何条件为 true 时求值为 true，或者在所有条件都为 true 时才求值为 true。
The where clause directs the program to discard particular tuples if they do not meet particular conditions.
如果特定的元组不能满足特殊条件，那么 where 子句命令程序废弃这些元组。
In addition, the return clause in this query contains conditional logic to determine if an E-mail element is present in a given customer's record.
此外，这个查询中的return子句包含一个条件逻辑，用于判断给定客户的记录中是否存在e - mail元素。
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