How Multiple Filters Operate
This section describes how multiple filters are used to process a non-uniform data files, files whose various rows exhibit varying data formats.
Each filter that you define is added to the wizard by means of the Add button on the Text Import Wizard - Step 2 dialog. The order in which you add the filters is critical because the order determines which filter is applied to a particular line when that line satisfies more than one filter.
It is possible for a single line in a data file to satisfy the conditions of more than one filter.
The wizard makes a single pass through the data file, reading one line at a time. To each line, the wizard applies the filters in the order in which they were added to the list on the Text Import Wizard - Step 2 dialog. The filters are applied one-at-a-time until one of them successfully matches the particular row of data, or until they all fail. A match occurs when a data line satisfies the filter's Include parameters, defined on the Text Import Wizard - Step 2 dialog.
Once a match occurs between the data line and a filter, the data line is imported according to all the parameters specified in the corresponding filter. After importing the data line, the wizard moves on to the next line in the data file. If no match occurs even after all filters have been attempted, the data line is ignored, and the wizard moves on to the next line in the data file.