002 Postgres Command Line : psql : Enabling extensions (PostGIS) to a database

So you have an existing database in PostGres that you wish to add the PostGIS extension to.

You will need to be logged in with a username that has superuser privileges.
Here let me do this using the postgres default account that on my instance has superuser access.

Here rather than logging in at the start I am choosing to change the connection to a different database

This is done by using

\c DatabaseName;

or

\connect DatabaseName;

Please note that the semicolon is vital in performing the instruction.

The way I have discovered to do this is by opening the database and then allocating the postgis extension to the database once it is open.

Let us first examine the tables in our blank database before the extension is enabled.

\dt

Now let us enable the extension.

CREATE EXTENSION postgis;

Let us now examine the database tables

\dt

Enabling the PostGIS extension adds this table along with the ability to add geometry types of varaibles within tables.

001 Postgres Command Line : psql : Getting Started with Postgres

I am just getting into PostGres and here are some rough notes for my reference.

Assuming you have a postgres admin account you want to sign in first of all and create a database

To find the command line go to search in Windows and type psql

Ensure that your postgres engine is running firstly

You should be presented with the following

There are default connections to the local host keep hitting these initially until you reach the following;

You will now need to know your password enter it here and press return

I will deal with the warning message further in the post – but a lot of people experience this message so I wanted to keep it in at present.

From my initial investigations as ever it is a good idea to restrict users to particular privileges at this level I am not being particularly refined – I would like to have a poweruser role that I can allocate to people and give this a defined password.

Signing in you can check out the roles and users as follows – on starting up a new instance you may well see something like this \du

So here I try and set up a user called general and create a role called general which I give create DB rights

I would recommend something stronger than the classic password password.

Issuing the \du command again we get to see the roles

Now we can close down and go back in but this time login as username general by altering the appropriate item when asked.

Note how the =# characters have been replaced by => this appears to denote the non superuser sign in.

To identify what username you are logged in as type \c at the prompt

My investigations suggest that the # sign denotes that you are logged into the database as superuser.

So first of all lets get rid of that annoying warning message when you log in at psql

I am running Postgres version 9.5 your version may vary but you can remove the warning by editing runpsql.bat file every version of postgres has this file and it will be located in the version equivalent directory to 9.5 for me.

C:\Program Files\PostgreSQL\9.5\scripts

Add the line

cmd.exe /c chcp 1252

as per underline and save the file

Now fire up psql as usual you should get the following

It should be noted that if you REM out the SET statements you can choose login with particular server / localhost / database / port and username presets which may be useful if you find yourself constantly going into a particular database as a particular user.

Here you see that the warning note has stopped.

It should be noted that using the general username you will NOT be able to create Databases

In order to CREATE databases you will have to be signed in with a username with sufficient privileges here I am in as postgres and I create a database called ExampleDB

You can see that on carrying out a successful command we usually see a repeat of the command.

To get a list of all databases in the instance type

\l

It can be seen that despite typing the name in capitals the database has been created in lower case this seems to be a feature of commandline. If you desperately want capitals you may need to go to pgadmin tool.

I think I’ll end it there for now.

MS Access Front End – Linked to PostGreSQL back end – a simple walk through using Access 2003

As I have indicated before MS Access makes a brilliant ETL tool. Important in this is being able to connect to different databases. I have set out how to connect to MySQL and SQLAzure before – the following sets out how to connect to PostGres.

To follow along you will either need PostGres installed on your local computer or alternatively all required connection parameters to a database in the cloud or on your lan.
PostGres Download

You will also need to Download and install a PostGreSQL ODBC driver – these are available at the following(March 2018).

PostGres ODBC Drivers

Scroll down the list – here I went to the bottom and obtained x64 version – MSI are downloaded (Microsoft Windows Installer files) – Install and then move to the next step.

Next create a blank database and right click in the white area to reveal a menu – select link tables.

You should now be presented with the Select Data Source dialog. Here I hit New…

This brings up the Create New Data Source dialog which lists database drivers scroll down through the list to PostgreSQL Unicode and select

Give your DSN an appropriate name and then go back to link table but this time rather than hitting the new button navigate to where you saved your DSN and select it and press OK.

The ever important parameters – you just need to know these – if you set up PostGres and you can get in through PG Admin selecting properties on the database should reveal the panel that will give you some guidelines. You may wish to double click on the image below so you can get a closer link of how I place my parameters in. I have opened the PGAdmin dialog here and placed it alongside the MS Access database window to show the properties I am transferring across.

Hitting OK should present you with the tables in your database.

And here is a demonstration with the link in place along with the table open and a simple form shown.

QGIS – Import shape file into PostGIS Table

The following uses
QGIS 2.14.2 Essen and
PostGres 9.5

A number of local authorities have released information through the UK’s data government site. The following example uses a shape file obtained from Lichfield District Council – At 2nd of October 2016 this was available for download from the following link

Lichfield Planning Applications

Open up QGIS and add Lichfield’s planning application shape file
qgisessen2142

Now scan along the top menu and go to Database

Select the sub menu DB Manager and then DB Manager

dbmanager

The following windows dialog should appear

dbmanagerdialog

Expand the area on the left named PostGIS – any PostGIS instances that you have created should be visisble here. Note you will have to have the PostGIS server running. Then highlight the actual instance that would like to import information into.

In this case I use the instance LocalPostGres

dbmanagerdialog

Choose the third icon from the left.
dbmanagerimportlayerfile

It should be noted that the window on the right may or may not show the correct connection to the database on the right.

importdialog

Name the table you wish to create and then hit OK – additional parameters are available.
There will be a delay before a confirmation of successful import happens – try to not issue commands during this time – once confirmation has been received go back into the PostGIS option and add the layer.

Connecting to PostgreSQL 9.3 from QGIS 2.8.1 – local host

First ensure that you have both Postgres and QGIS installed on your machine.

In order for you to be able to connect to Postgres from QGIS on local host you must ensure 2 things. Firstly that the PostGIS plugin has been installed on your laptop AND secondly that you have included the postgis extension in each database that you wish to connect to. Without enabling the extension in the database you won’t be able to connect OR import shape files. Installation of PostGIS is often a default during the install of postgres but you can check whether this was completed correctly by using the Application Stack Builder, a small program that is installed with later versions of postgres.

I navigated to this on the win 8.1 machine I was using by using search.

Opening application stack builder you will be presented with the following.

ApplicationStackBuilder

Expand the spatial extensions tree to identify if you already have the PostGIS plugin installed – if not – select as appropriate the plugin and you will be prompted to install. You will need an internet connection for this. Above you can see that my plugin was already installed.

Next you need to add the PostGIS extension to each Postgres database you wish to link to from QGIS this is done through PG Admin.

This is something that both myself and a colleague got caught out by and it took me an hour of searching to find how to fix it.

Below I have a database called GISData which I have just created. You will note there is only one object within the expanded extensions tree. You will not be able to connect to a database that does not include PostGIS in its list of extensions
CreateExtension

Hi-light the database you want to spatially enable then go to Tools – Query Tool( Ctrl + E will do the same). In the above picture I’ve slightly jumped the gun. To add the extension to the database type.

CREATE EXTENSION postgis

Run the query by selecting the green right arrow
There will be a short delay and then upon refresh of the connection postgis should appear in the list of extensions.

CreateExtensionCreated

You can now close the Postgres administrator and return to QGIS where you should be able to setup the connection to the database.

Parameters should be similar to below and it is useful to test the connection prior to saving.

SettingupthePostGISconnection