Bộ lọc và Phân loại xứng đáng một số sự chú ý đặc biệt. Nếu bạn đã từng làm việc với một cơ sở dữ liệu Microsoft Access, bạn sẽ biết cách dễ dàng các công cụ giao diện đồ họa có cho phép bạn viết các truy vấn mà không cần viết bất kỳ mã SQL. | Using the Quantum DB Plug-In Filter and Sort deserve some special attention. If you have ever worked with a Microsoft Access database you will know how easily the GUI tools there allow you to write queries without writing any SQL code. The Quantum Table View s Filter and Sort function works in similar fashion. To use the Filter and Sort functions you ll need to double-click on the tCat table directly from the Database Bookmarks view. You can also right-click on the table name and select View T able from the contextual menu. Both of these options are equivalent to a select statement. The T able View will populate with the results from the query. Be aware that to use Filter and Sort you need to populate the T able View by either one of the aforementioned methods doubleclicking on the table or selecting View T able from the table s contextual menu. You cannot simply write a select statement in the SQL editor and then use Filter and Sort even though the same result set will be in the Table View. Once you have the result set up click on the Filter and Sort icon. You will get this screen This wizard dynamically creates a where clause for your select statement. You set the values shown below to create your where clause Where is the column criteria that you wish to specify. Operator allows you to test if the criteria are equal to not equal to less than or greater than . Click on this column in the row you wish to test for a pull-down menu of all the available operators. Values are the criteria to test. This is a freeform textbox where you enter the value you want to test. 150 Chapter 6 If the value is a string check the checkbox in the Is String column. This will add single quotes to the Values you specify. Otherwise the filter assumes that the column is an integer and thus does not require quotation marks. You can also specify an Order By clause for the query. Sorter allows you to select if the Order By is to be ascending or descending. For example let s create a filter .
