Attribute table, filters and the field calculator

The attribute table shows one row per feature and one column per field. Select a layer and press T, or choose Layer → Attribute table. It opens below the map.

Sort, select and edit

Click a column heading to sort, click it again to reverse. The button in the first column selects the feature and moves the map to it; Shift adds to the selection. Edit opens all attributes of a feature in a dialog; a double-click on a value edits it in place (Enter saves, Escape cancels). Add field… and Delete field… change the columns; Export CSV downloads the table.

Filters

A filter hides features that do not match an expression. Choose Filter… in the table or Layer → Filter features… and write, for example:

zone = 'residential' AND population > 1000

The map, the feature list, the table and exports by default then only show the matching features. In Town districts, three of six districts match: Seefeld, Moosmatt and Rebhalde. The layer list shows 3 of 6.

The expression language

Expressions work like SQL or QGIS:

• text in single quotes ('mixed'), field names as they are or in double quotes ("Name with space");
• + - * / % ^, || joins text, comparisons = != < <= > >=;
• AND, OR, NOT, LIKE 'A%', ILIKE, IN ('a', 'b'), IS NULL, BETWEEN 1 AND 3;
• functions: abs, round, floor, ceil, sqrt, ln, exp, pow, min, max, upper, lower, trim, length, substr, replace, concat, coalesce, if, to_number, to_string and pi;
• geometry values $area (m²), $length (m), $perimeter (m), $x, $y and $id.

Empty values are NULL: NULL + 1 is NULL, and a comparison with NULL is neither true nor false. Expressions never run JavaScript; an unknown field or function is reported with its position.

Field calculator

Field calculator… writes the result of an expression into a new or existing field. For population per square kilometre:

round(population / ($area / 1000000))

The dialog shows the first five results before you calculate; for Altstadt that is 3650. $area is measured on the WGS 84 ellipsoid, so the result is correct in any coordinate system. Tick Only the selected features to update part of a layer.

Join a CSV table

Join CSV… adds columns from a table to the features whose key matches — for example mayors or school counts per district name. Choose the key field of the layer and the key column of the CSV; numbers are recognised, and the status line says how many features matched and how many did not.