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	Executing your first SQL queries
2011 January 28

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You can follow two different approaches in order to query a DB table:

you can lazily use the Query Table menu item.
1. this surely is quickest and easiest way, completely user friendly.
2. you simply have to click the mouse's right button over the required table, so to make the context menu to be shown.
3. then you can simply use the lowermost buttons in order to scroll the result-set back and forth at your will.
4. anyway, this approach is rather mechanical, and doesn't allow you to exploit SQL at the best of its powerful capabilities.
alternatively you can hand-write any arbitrary SQL statement into the uppermost pane, then pressing the Execute button.
1. this one is the hardest way: you are responsible for what you are doing (or even misdoing ...)
2. but this way you can take full profit of the impressive SQL unconstrained fire power.

You surely noticed in the above illustration that Geometry columns simply reports an anonymous BLOB GEOMETRY: this is far to be satisfactory.
But you can get a much richer preview of any Geometry simply clicking the mouse's right button over the corresponding value, then selecting the BLOB explore menu item.

SELECT COL002 AS name,
  COL006 AS longitude,
  COL005 AS latitude,
  MakePoint (COL006, COL005, 4326) AS geom
FROM cities1000
WHERE COL009 = 'IT';

You can test how free-hand SQL works using this SQL statement: simply copy the above SQL statement, then paste into the query pane, and finally press the Execute button.
Just a quick and fast explanation:

the cities1000 table contains any populated place in the world
there are lots of columns in this table, and their names are rather obscure
(you can find a full documentation for this at http://www.geonames.org/)
but you can simply trust to my authority just for now.
COL002 contains the name of each populated places.
COL006 contains the corresponding longitude (expressed in decimal degrees).
COL005 is the corresponding latitude
MakePoint() is a Spatial function building a point-like Geometry from corresponding coordinates.
COL009 contains the Country code
very simply said, the WHERE clause will filter the result-set so to exclude all places outside Italy.

All right, you are now supposed to be able to really start working seriously.
In the next slides we'll start exploring the mystery world of SQL and Spatial SQL.

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	Author: Alessandro Furieri a.furieri@lqt.it
	This work is licensed under the Attribution-ShareAlike 3.0 Unported (CC BY-SA 3.0) license.

	Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.