<s>
In	O
SQL	B-Language
,	O
the	O
TRUNCATE	B-Language
TABLE	I-Language
statement	O
is	O
a	O
Data	B-Language
Definition	I-Language
Language	I-Language
(	O
DDL	O
)	O
operation	O
that	O
marks	O
the	O
extents	O
of	O
a	O
table	B-Application
for	O
deallocation	O
(	O
empty	O
for	O
reuse	O
)	O
.	O
</s>
<s>
The	O
result	O
of	O
this	O
operation	O
quickly	O
removes	O
all	O
data	O
from	O
a	O
table	B-Application
,	O
typically	O
bypassing	O
a	O
number	O
of	O
integrity	O
enforcing	O
mechanisms	O
.	O
</s>
<s>
It	O
was	O
officially	O
introduced	O
in	O
the	O
SQL:2008	B-Language
standard	O
,	O
as	O
the	O
optional	O
feature	O
F200	O
,	O
"	O
TRUNCATE	B-Language
TABLE	I-Language
statement	O
"	O
.	O
</s>
<s>
TRUNCATE	B-Language
TABLE	I-Language
removes	O
all	O
rows	O
from	O
a	O
table	B-Application
,	O
but	O
the	O
table	B-Application
structure	O
and	O
its	O
columns	O
,	O
constraints	O
,	O
indexes	O
,	O
and	O
so	O
on	O
remain	O
.	O
</s>
<s>
To	O
remove	O
the	O
table	B-Application
definition	O
in	O
addition	O
to	O
its	O
data	O
,	O
use	O
the	O
DROP	O
TABLE	B-Application
statement	O
.	O
</s>
<s>
The	O
TRUNCATE	B-Language
TABLE	I-Language
mytable	O
statement	O
is	O
logically	O
(	O
though	O
not	O
physically	O
)	O
equivalent	O
to	O
the	O
DELETE	B-Language
FROM	O
mytable	O
statement	O
(	O
without	O
a	O
WHERE	B-Language
clause	O
)	O
.	O
</s>
<s>
The	O
following	O
characteristics	O
distinguish	O
TRUNCATE	B-Language
TABLE	I-Language
from	O
DELETE	B-Language
:	O
</s>
<s>
In	O
the	O
Oracle	B-General_Concept
Database	I-General_Concept
,	O
TRUNCATE	B-Language
is	O
implicitly	O
preceded	O
and	O
followed	O
by	O
a	O
commit	B-Language
operation	O
.	O
</s>
<s>
(	O
This	O
may	O
also	O
be	O
the	O
case	O
in	O
MySQL	B-Application
,	O
when	O
using	O
a	O
transactional	O
storage	O
engine	O
.	O
)	O
</s>
<s>
Typically	O
,	O
TRUNCATE	B-Language
TABLE	I-Language
quickly	O
deletes	B-Language
all	O
records	O
in	O
a	O
table	B-Application
by	O
deallocating	O
the	O
data	O
pages	O
used	O
by	O
the	O
table	B-Application
.	O
</s>
<s>
This	O
reduces	O
the	O
resource	O
overhead	O
of	O
logging	B-General_Concept
the	O
deletions	O
,	O
as	O
well	O
as	O
the	O
number	O
of	O
locks	B-Operating_System
acquired	O
.	O
</s>
<s>
Two	O
notable	O
exceptions	O
to	O
this	O
rule	O
are	O
the	O
implementations	O
found	O
in	O
PostgreSQL	B-Application
and	O
Microsoft	B-Application
SQL	I-Application
Server	I-Application
,	O
both	O
of	O
which	O
allow	O
TRUNCATE	B-Language
TABLE	I-Language
statements	O
to	O
be	O
committed	O
or	O
rolled	O
back	O
transactionally	O
.	O
</s>
<s>
It	O
is	O
not	O
possible	O
to	O
specify	O
a	O
WHERE	B-Language
clause	O
in	O
a	O
TRUNCATE	B-Language
TABLE	I-Language
statement	O
.	O
</s>
<s>
TRUNCATE	B-Language
TABLE	I-Language
cannot	O
be	O
used	O
when	O
a	O
foreign	O
key	O
references	O
the	O
table	B-Application
to	O
be	O
truncated	O
,	O
since	O
TRUNCATE	B-Language
TABLE	I-Language
statements	O
do	O
not	O
fire	O
triggers	B-Language
.	O
</s>
<s>
This	O
could	O
result	O
in	O
inconsistent	O
data	O
because	O
ON	O
DELETE/ON	O
UPDATE	O
triggers	B-Language
would	O
not	O
fire	O
.	O
</s>
<s>
In	O
some	O
computer	O
systems	O
,	O
TRUNCATE	B-Language
TABLE	I-Language
resets	O
the	O
count	O
of	O
an	O
Identity	B-Language
column	I-Language
back	O
to	O
the	O
identity	O
's	O
seed	O
.	O
</s>
<s>
In	O
Microsoft	B-Application
SQL	I-Application
Server	I-Application
2000	O
and	O
beyond	O
in	O
full	O
recovery	O
mode	O
,	O
every	O
change	O
to	O
the	O
database	O
is	O
logged	O
,	O
so	O
TRUNCATE	B-Language
TABLE	I-Language
statements	O
can	O
be	O
used	O
for	O
tables	O
involved	O
in	O
log	B-General_Concept
shipping	I-General_Concept
.	O
</s>
