Calculating two columns at once in QGIS

Question

Is it possible to calculate two columns at once?

So what I mean is that we have different covers and lengths and I want a total length of "Cover A" after that a total length of cover tb and so on.

See that attached photo for the columns that I mean.

Answer 1

QGIS has an algorithm for that :

• Statistics by categories (official documentation)

You have to select your layer, your category field (here "Cover") and the field to calculate statistics (here "Length"). It will create a new non-geographic layer with your categories and some new statistic fields as minimum, maximum, mean, sum, etc.

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You can also do a "Virtual Layer" through Layer > Add Layer > Add/Edit Virtual Layer... with a SQL query :

SELECT
    "Cover",
    SUM("Length") AS total_length
FROM
    your_table_name
GROUP BY
    "Cover"