[postgis-users] Bounding Box Query

[iheanyi Okeh]

Hi David,
I understand what this query below is doing.

SELECT str_num || ' ' || name as full_address,
    distance(the_geom,'POINT(2227284.1963667543
1435389.6730164126)'::geometry) as dist
    FROM address
ORDER BY dist limit 1

I managed to write.

What I don't understand is how the values of the bounding box below is 
derived.

WHERE the_Geom && expand('POINT(2227284.196366754
1435389.6730164126)'::geometry, <max distance>) )


Notice the arguments 'POINT(2227284.196366754
1435389.6730164126)'::geometry are the same as the x,y coordinate pair in 
the select statement.
It helps to know what you are doing rather than just copying codes and 
pasting.
So I can just understand how the arguments in the where clause are 
generated, it will help with future queries and functions.
I looked at several instances where this:
WHERE the_Geom && expand('POINT(2227284.196366754
1435389.6730164126)'::geometry, <max distance>) ) is used but I can't seem 
to find an explanation of where those arguments in the && 
expand('POINT(....)' came from.

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