qgis - How to load a style from POSTGIS in PyQt

The thing is that I have four styles I have created in QGIS through the GUI and saved into a postgresql database.

I can see them in the table named layer_styles

I have seen similar questions asking to load from qml file, or even from a database, like that but it looks as if I need to get a styled layer before for get the style from it.

It's like I say or can I load the styles from database without a styled layer?

Anyway I don't know how must I do to get the styles and use it for another layers

Answer

Well, this is my try to load a style stored in Postgres database. QGIS saves the layers in a table called layer_styles The column I need is styleqml, so I need to make a query like that:

select styleqml from public.layer_styles;

There are another descriptive columns like stylename or description I can use for help to choose the properly style. I could do:

select stylename, description, styleqml from public.layer_styles;

I have used only styleqml column and I have stored all the records in a list

Finnally I only have to set the style in my layer like that:

self.vlayer.applyNamedStyle(mylist[n])

I show a snippet of my code. Sorry if there are mistakes or if I am saying any silliness, but it works for me:

self.loadStyles = QtSql.QSqlQuery(self.conexion)
self.listOfStyles=[]
if self.loadStyles:
    self.loadStyles.exec_("SELECT styleqml FROM public.layer_styles")           
    while self.loadStyles.next():
        self.listOfStyles.append(unicode(self.loadStyles.value(0)))
self.myStyle = self.listOfStyles[1] # 1 in my case      
self.vlayer.applyNamedStyle(self.myStyle)