MySQL concatenation when there are null fields - mysql

Question

I created a VIEW using this code:
CREATE OR REPLACE VIEW aaa AS
SELECT pry.uid,
treg.nombre_es as region,
tpais.nombre_es as pais,
tdep.departamento,
dep_other, tciu.ciudad,
ciu_other
FROM tx_oriproyectos_proyectos AS pry
LEFT JOIN tx_oritablascomunes_regiones as treg ON pry.region = treg.uid
LEFT JOIN tx_oritablascomunes_paises as tpais ON pry.pais = tpais.uid
LEFT JOIN tx_oritablascomunes_departamentos as tdep ON pry.departamento = tdep.uid
LEFT JOIN tx_oritablascomunes_ciudades as tciu ON pry.ciudad = tciu.uid
And I obtained this and is Ok:
result http://finewebdesigns.com/images/mysql_view_result.jpg
And now I need to obtain concatenate results like this:
concatenated_field
---------------------------------------
Africa - ALbania - Tirana1 - Tirana2
Africa - Colombia - Guaviare - Calamar
How can I do that?
I tried this:
CREATE OR REPLACE VIEW aaa AS
SELECT CONCAT_WS (' - ', pry.uid, treg.nombre_es as region, tpais.nombre_es as pais, tdep.departamento, dep_other, tciu.ciudad, ciu_other)
FROM tx_oriproyectos_proyectos AS pry
LEFT JOIN tx_oritablascomunes_regiones as treg
ON pry.region=treg.uid
LEFT JOIN tx_oritablascomunes_paises as tpais
ON pry.pais=tpais.uid
LEFT JOIN tx_oritablascomunes_departamentos as tdep
ON pry.departamento=tdep.uid
LEFT JOIN tx_oritablascomunes_ciudades as tciu
ON pry.ciudad=tciu.uid
But I obtained:
#1583 - Incorrect parameters in the call to native function 'CONCAT_WS'
Ok, Thanks to #Mat I finally get this code, that is the expected solution to this problem.
CREATE OR REPLACE VIEW aaa AS
SELECT pry.uid, CONCAT_WS (' - ', treg.nombre_es, tpais.nombre_es, tdep.departamento, NULLIF(dep_other,''), tciu.ciudad, NULLIF(ciu_other,''))
FROM tx_oriproyectos_proyectos AS pry
LEFT JOIN tx_oritablascomunes_regiones as treg
ON pry.region=treg.uid
LEFT JOIN tx_oritablascomunes_paises as tpais
ON pry.pais=tpais.uid
LEFT JOIN tx_oritablascomunes_departamentos as tdep
ON pry.departamento=tdep.uid
LEFT JOIN tx_oritablascomunes_ciudades as tciu
ON pry.ciudad=tciu.uid
That obtains this: http://finewebdesigns.com/images/mysql_view_result_solved.jpg

Answer 1

You should be able to use the CONCAT_WS string function.
SELECT CONCAT_WS(' - ', treg.nombre_es, tpais.nombre_es, ...) FROM ...
From the docs:
CONCAT_WS() does not skip empty strings. However, it does skip any NULL values after the separator argument.
so your null values will simply be ignored.
If you also want to skip empty strings, you can use throw the NULLIF function in the mix, as suggested by ypercube:
SELECT CONCAT_WS(' - ', NULLIF(col,''), ...) ...