第一个条件陈述式用于输入验证。
The first conditional statement is used for input validation.
一般来说，您会想要使用筛选条件或参数来限制资料录的选取，可能会采用 排序资料录或自订SQL陈述式等方式。
Typically, you want to constrain the record selection with a filter or parameters, perhaps sort the records, customize the SQL statement.
加入、移除，或变更条件式编译陈述式的评估运算式。
Adding, removing, or changing the evaluation expression of a conditional compilation statement.
依据运算式的值，有条件的执行一组陈述式。
Conditionally executes a group of statements, depending on the value of an expression.
依据运算式的值，有条件的执行一组陈述式。
Conditionally executes a group of statements, depending on the value of an expression.
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