You must place the variable between square brackets (=[x]) to create a query with variable parameters. Alternatively, you can use an equal sign followed by a colon (=:x). When the query is executed, the program will display a dialogue box asking you for the expression to which the variable x should be assigned.
如果需要建立带有变量参数的查询，则必须在变量前后加上方括号 (=[x])，或者在等号后加上冒号 (=:x)。在执行查询时，程序会显示一个对话框，询问您要将变量 x 指定给哪个表达式。