Non-Spatial Queries#

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Manual selection#

  • Select the features manually in the attribute table by clicking on it.

  • Holding Ctrl while selecting features lets you select multiple features at once.

Example: Manually select countries with the attribute table

Select by expression#

The Select by Expression tool lets you build an expression to select features of a layer. For example, you can select specific attributes, or select features where the value of an attribute in a specific range.

  1. Open the attribute table and select the Select by Expression-tool.

  1. The expression builder will open.

Comparison operators#

  • >, <, =, !=

Example: Select all cities with more than 20 million inhabitants in 2015: "2015" > 20000

Special operators#

  • LIKE

Example: Select all countries in Asia: "continent" LIKE 'asia'

Logical operators#

  • AND, OR

  • Can be used to combine different queries or criteria.

Example: Cities, not having a population of one million inhabitants in 1950, had surged to over 10 million inhabitants by 2015: "1950" < 1000 AND "2015" > 10000

Complex Expressions#

It is also possible to add expressions that chain different requirements. In this case do not forget to put brackets around individual parts of the expression such as:

Save selected features as a new file#

  • Layer-Properties -> Export -> Save only selected features

Example: Export selected features as a new file

Select by expression options#

operator

functionality

+

addition

-

subtraction

*

multiplication

/

division

%

remainder of division

operator

functionality

=

equals

!=

not equal

<

less than

>

greater than

<=

less than or equal to

>=

greater than or equal to

Operators such as AND, OR can be used to combine different queries or criteria

operator

functionality

AND

logical AND

OR

logical OR

NOT

logical NOT

operator

functionality

LIKE

pattern matching

IN

checks if a value is in a list of values

IS NULL

checks for null values

BETWEEN

checks if a value is within a specified range

CASE WHEN

conditional expressions

Further resources#

You can access information about logical operators in QGIS documentation through the following link.