<s>
Astronomical	B-Language
Data	I-Language
Query	I-Language
Language	I-Language
(	O
ADQL	B-Language
)	O
is	O
a	O
language	O
for	O
astronomical	O
data	O
query	O
based	O
on	O
SQL	B-Language
92	O
.	O
</s>
<s>
ADQL	B-Language
is	O
a	O
specialized	O
variant	O
of	O
the	O
SQL	B-Language
query	B-Language
language	I-Language
adapted	O
for	O
accessing	O
the	O
astronomical	O
datasets	O
of	O
the	O
virtual	B-Application
observatory	I-Application
,	O
via	O
the	O
Table	O
access	O
protocol	O
(	O
TAP	O
)	O
.	O
</s>
<s>
ADQL	B-Language
is	O
dedigned	O
to	O
handle	O
large	O
datasets	O
distributed	O
over	O
several	O
locations	O
,	O
while	O
not	O
retrieving	O
data	O
that	O
is	O
not	O
needed	O
.	O
</s>
<s>
ADQL	B-Language
is	O
a	O
query	B-Language
language	I-Language
that	O
allows	O
data	O
to	O
be	O
retrieved	O
via	O
a	O
single	O
command	O
,	O
the	O
select	O
statement	O
,	O
which	O
is	O
designed	O
to	O
perform	O
as	O
the	O
select	O
statement	O
in	O
the	O
SQL	B-Language
language	I-Language
.	O
</s>
<s>
ADQL	B-Language
has	O
extensions	O
designed	O
to	O
improve	O
handling	O
of	O
astronomical	O
data	O
such	O
as	O
spherical	O
co-ordinates	O
that	O
are	O
not	O
handled	O
by	O
standard	O
SQL	B-Language
.	O
</s>
<s>
ADQL	B-Language
is	O
implemented	O
in	O
packages	O
such	O
as	O
TOPCAT	B-Application
.	O
</s>
