QGIS » QGIS Application

In the layer properties in QGIS Desktop, add the ability to specify the type of Join of two layers. At present only an INNER JOIN is performed.



For example, I wish to implement the following equivalent code within QGIS

i.e. I want to display all records, which have a parent with name "xx"



SELECT * FROM table_1, table_2, table_3

WHERE table_1.foreign_key = table_2.key AND table_3.foreign_key = table_2.key AND

table_2.parent_key = (SELECT table_3.foreign_key, WHERE table_3.name = "xx")



From the following MS SQL Server tables

table_1

with fields - id, foreign_key, geom

table_2

with fields - key, parent_key, etc.

table_3

with fields - id2, foreign_key, name, preferred



Tables 1 and 2 are of the same length

The field "parent_key" allows the objects to be arranged in a hierachical fashion.

Table 3 allows several names to be attached to the same object, with the field "preferred" indicating the preferred name. Hence table_3



is longer than table_2.



At present, if the 3 tables are joined within the Layer properties, then only the first entry from table_3 is included, rather than what is required are all rows, so that the preferred names can be selected.