How to add a lib to a qt project

[WilliamSpiderWeb]

Hello,

I'm using qt4 on a Windows 7 system and I'm trying to get access to a PostgreSQL 9 DB.

That's why I'm trying to add libpg.lib (with libpg-fe.h) to my project. But I'm doning something wrong.

I added "LIBS += -lpg" to my projectfile *.pro.

QT       += core gui
 
TARGET = SQL_BSP
TEMPLATE = app
 
LIBS += -lpg
 
SOURCES += main.cpp\
        mainwindow.cpp \
    postgresqldb.cpp
 
HEADERS  += mainwindow.h \
    libpq-fe.h \
    postgres_ext.h \
    postgresqldb.h
 
FORMS    += mainwindow.ui
 
OTHER_FILES += \
    libpq.lib

QT       += core gui
 
TARGET = SQL_BSP
TEMPLATE = app
 
LIBS += -lpg
 
SOURCES += main.cpp\
        mainwindow.cpp \
    postgresqldb.cpp
 
HEADERS  += mainwindow.h \
    libpq-fe.h \
    postgres_ext.h \
    postgresqldb.h
 
FORMS    += mainwindow.ui
 
OTHER_FILES += \
    libpq.lib

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When I start compiling my project I get the following error message:

cannot find -lpg
collect2: ld returned 1 exit status

cannot find -lpg
collect2: ld returned 1 exit status

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I'm waiting for your help.
Thanks,
Alex