The WHERE clause
Interface
is used to define the restriction used to generate a new dataset. The
restriction can involve one or more datasets, using standard and/or spatial attributes (vertical
tabs). The
list of operators supported is adjusted to the type of attributes involved.
The operators <,>,<=,>=,<>,=, LIKE, NOT are
used with standard attributes comparison, and the spatial operators
such as ST_UNION, ST_INTERSECTION, ST_AREA among others are used to
operate over geometric attributes.
To define a restriction based on Attributes follow the steps:
Select restriction type on the vertical tab:
Attribute,
Define a restriction by selecting:
Property
Operator (>, >=, <, <=, = )
Value - it can be a property of other dataset or a value among all values of the property chosen.
Property
Value
Click on to add this combination (property x operator x value) to the Table/SQL tabs bellow.
On the frame Table/SQL it is possible to handle the restriction adding more clauses, removing one or all lines, or checking the SQL generated:
Check the list of restrictions.
Define the connector (and, or, nothing) and the next restriction.
Clear all restriction using or only one line using .
Optionally, change to SQL tab to see the restriction generated in SQL.
Go to the step 1 to define the next part of the restriction as necessary.
To define a restriction based on spatial attributes follow the steps:
Select restriction type on the vertical tab:
Spatial
Define a restriction by selecting:
Property - geometry attribute of the selected dataset
Operator (ST_Contains, ST_Union, ST_Crosses, ...)
Layer - select the layer to be confronted with the restriction defined.
Use Selected Objects - check this option if the goal is to apply the restriction only over the selected objects in the layer displayed.
Click on to add this combination (property x operator x value) to the Table/SQL tabs bellow.
On the frame Table/SQL it is possible to handle the restriction adding more clauses, removing or checking the SQL generated:
Check the list of restrictions.
Define the connector (and, or, nothing) and the next restriction.
Clear all restriction using or only one line using .
Optionally, change to SQL tab to see the restriction generated in SQL.
Go to the step 1 to define the next part of the restriction as necessary.