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This mini-tutorial provides a basic understanding of how to create filter and in what cases to use it.
What is Data Filtering?
Data filtering is the most advanced method to extract definite data. Appling filters user can set complex conditions and as a result receive complete information on specific criteria separating all the rest records from a table.
In short, filtering is a quick way to show only the data that you need.
Why can you apply Filtering?
Filtering seems to be especially useful when you need to process tables with large bulk of data. Using filters, it is possible to handle only the records that meet your precise criteria in a second.
DBConvert tools provide easy-to-use data filtering assignment that can be applied to all tables in MySQL, MS SQL, MS Access, PostgreSQL and FoxPro databases for partial conversion. You can simultaneously determine multiple criteria for a table.
Filters can be classified into two types: elementary and complex filters.
1. As an example for elementary filter we can retrieve all records in the "Date" and "Permission" columns, grouped by user name.
2. For complex filter building, shown schematically below, we need to group data concerning users' "Permissions" and their "Time" connection in a destination table.
Building and Using Filters
Choose a table meant for filter using at the "Customization" stage and click "Filter" button.
"Filter" window consists of three parts:
1."New condition" - here you can select one or multiple conditions for filter.
To create a filter, you need to specify three elements:
- Choose a table field for which you want to retrieve data
- Choose possible filter operations (not null, equal to, less than etc.)
- Choose filter value
After defining the necessary information, click "Add condition" button. Your selected filtering conditions are transformed in SQL query shown in "Preview" area.
If you need to display several queries simultaneously use "AND" / "OR" operators.
2."Selected conditions" part reflects the list of all defined filters specified before.
If you want to delete any condition, please select the required condition and press "Remove condition" button.
3. To display selected data, click "Refresh" button on the "Preview" GroupBox and you will see the result of effected filters.
After pressing "Add condition" button determinate data range and corresponding SQL query will be built automatically if "Refresh automatically on query change" option is checked.
"Query" line displays your filter in the form of the SQL query. If you change your filter with the aim to add or edit condition, "Query" line is updated and re-built automatically.
Users can change the query manually and re-execute the data retrieving.
Conclusion
As you can see it is possible to create new filters on the base of query and easily modify existing queries by adding your own conditions manually. Enabling filters in your conversion process you can reduce time required for migration of all info and retrieve only needed.
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