Update Column allows you to change a column's value by updating a table based on its own data values or by updating a table based on data from another table. This dialog box remembers the column that was updated the last time update was run and the expression that was used for updating a column the last time an update was run.
Table to Update
Use this drop-down list to specify the table you want to update or where MapInfo Pro should create the temporary column.
Column to Update
Choose the column to update if the Table to update is different than the table selected in Get Value From Table. Add temporary column displays in the list.
Add new temporary column
Choose Add new temporary column if you want to add a temporary column to the update table. This is where your results are stored.
Get Value From Table
This option is automatically set to the same table as Table to update. You can also choose a different table from which MapInfo Pro will retrieve the update information.
Value
Displays when you are working with only one table. Type an expression into the Value box or use the Assist button to access the Expression dialog box where you can create an expression.
Join button
Displays the Join dialog box. The Join button is active when the data table is different than the table to update. When updating a column using data from another table, use the Join dialog box to specify how records in the two tables are matched.
Calculate
When you select the Join button the Calculate field displays. The table from which you are retrieving the data dictates your choice of options.
- When you update one table based on its own data values, MapInfo Pro automatically chooses the value option.
- When you update one table based on data from another table, specify Value, Min, Average, Sum, Max, Count, Proportion Sum, WtAvg, Proportion Avg, or Proportion WtAvg.
Choose one of the following aggregate functions:
Count: Counts the number of records in a group. Takes * as its argument because it applies to the record as a whole and not to any particular field in a record.
Sum(expression): Calculates the sum of the values in expression for all the records in a group.
Average(expression): Calculates the average of the values in expression for all the records in a group.
Max(expression): Finds the highest value in expression for all records in a group.
Min(expression): Finds the lowest value in expression for all records in a group.
WtAvg: With weighted averaging, MapInfo Pro adjusts the calculation of averages so that the values from each selected object are weighted more or less heavily.
Proportion Sum: Aggregates data into a polygon. Accounts for the area of the polygon that overlaps the polygon receiving the aggregation. For example, if a third of an object's area falls within a polygon the proportion sum aggregate will put one third of the overlapping object's data value in the polygon.
Proportion Avg: Computes the average based on the proportion of values from the covered areas (weighs the averages according to area). For example, if 80% of a new object's area is from Object A having a mortality rate of .8% and 20% of the new object's area is from Object B having a birth mortality rate of .65%, then the birth rate of the object would be equal to .8 x .008 + .0065 x .2 = .0077 or .77%
Proportion WtAvg: Computes the average based on the proportion of values from the covered areas (weighs the averages according to another field whose value is proportioned). For example, (continuing from the example above), Population of the new object, Object A = 34,000. Population of new object, Object B = 26,000. The birth mortality rate is (.8 x 34,000 + .6 x 26,000) /6,000 = .713.
Of: Specify values stored in a single column or a mathematical expression based on values in one or more tables. Specify the field or build your own expression by choosing Expression from the drop-down list and using the Expression dialog box. expressions or fields are evaluated according to the selected Aggregate Function or Value. Value is automatically selected when you update one table based on its own data values.
Browse Results
Check the Browse results check box when you want to display an updated table. If you do not want to see the table, clear the box.
Assist button
You must be working with two tables to display the Assist button. If you wish to create an expression, click on the Assist button, the Expression dialog box displays.
Clear button
Clears the expression value edit box.
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