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<!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
<concept id="reserved_words">

  <title>Impala Reserved Words</title>
  <prolog>
    <metadata>
      <data name="Category" value="Impala"/>
      <data name="Category" value="Troubleshooting"/>
      <data name="Category" value="SQL"/>
      <data name="Category" value="Planning"/>
      <data name="Category" value="Developers"/>
      <data name="Category" value="Data Analysts"/>
    </metadata>
  </prolog>

  <conbody>

    <p>
      <indexterm audience="hidden">reserved words</indexterm>
      The following are the reserved words for the current release of Impala. A reserved word is one that
      cannot be used directly as an identifier; you must quote it with backticks. For example, a statement
      <codeph>CREATE TABLE select (x INT)</codeph> fails, while <codeph>CREATE TABLE `select` (x INT)</codeph>
      succeeds. Impala does not reserve the names of aggregate or scalar built-in functions. (Formerly, Impala did
      reserve the names of some aggregate functions.)
    </p>

    <p>
      Because different database systems have different sets of reserved words, and the reserved words change from
      release to release, carefully consider database, table, and column names to ensure maximum compatibility
      between products and versions.
    </p>

    <p>
      Because you might switch between Impala and Hive when doing analytics and ETL, also consider whether
      your object names are the same as any Hive keywords, and rename or quote any that conflict. Consult the
      <xref href="https://cwiki.apache.org/confluence/display/Hive/LanguageManual+DDL#LanguageManualDDL-Keywords,Non-reservedKeywordsandReservedKeywords" scope="external" format="html">list of Hive keywords</xref>.
    </p>

    <p outputclass="toc inpage"/>

  </conbody>

<concept id="reserved_words_current">
<title>List of Current Reserved Words</title>
<conbody>
<!-- This list is derived from the source code at:
     https://github.com/apache/impala/blob/master/fe/src/main/jflex/sql-scanner.flex

See the history, any recent changes, here:
     https://github.com/apache/impala/commits/master/fe/src/main/jflex/sql-scanner.flex
-->

<codeblock rev="ver">add
aggregate
all
alter
<ph rev="2.0.0">analytic</ph>
and
<ph rev="2.0.0">anti</ph>
<ph rev="1.4.0">api_version</ph>
as
asc
avro
between
bigint
<ph rev="1.4.0">binary</ph>
<ph rev="kudu">blocksize</ph>
boolean
<!-- <ph rev="kudu">buckets</ph> -->
by
<ph rev="1.4.0">cached</ph>
<ph rev="2.3.0">cascade</ph>
case
cast
change
<ph rev="2.0.0">char</ph>
<ph rev="1.4.0">class</ph>
<ph rev="1.2.1">close_fn</ph>
column
columns
comment
<ph rev="kudu">compression</ph>
compute
create
cross
<ph rev="2.0.0">current</ph>
data
database
databases
date
datetime
decimal
<ph rev="kudu">default</ph>
<ph rev="kudu">delete</ph>
delimited
desc
describe
distinct
<!-- <ph rev="kudu">distribute</ph> -->
div
double
drop
else
<ph rev="kudu">encoding</ph>
end
escaped
exists
explain
<ph rev="2.5.0">extended</ph>
external
false
fields
fileformat
<ph rev="1.2.1">finalize_fn</ph>
first
float
<ph rev="2.0.0">following</ph>
<ph rev="2.1.0">for</ph>
format
formatted
from
full
function
functions
<ph rev="2.1.0">grant</ph>
group
<ph rev="kudu">hash</ph>
having
if
<!-- <ph rev="kudu">ignore</ph> -->
<ph rev="2.5.0">ilike</ph>
in
<ph rev="2.1.0">incremental</ph>
<ph rev="1.2.1">init_fn</ph>
inner
inpath
insert
int
integer
intermediate
interval
into
invalidate
<ph rev="2.5.0">iregexp</ph>
is
join
last
left
like
limit
lines
load
location
<ph rev="1.2.1">merge_fn</ph>
metadata
not
null
nulls
offset
on
or
order
outer
<ph rev="2.0.0">over</ph>
overwrite
parquet
parquetfile
partition
partitioned
<ph rev="1.4.0">partitions</ph>
<ph rev="2.0.0">preceding</ph>
<ph rev="1.2.1">prepare_fn</ph>
<ph rev="1.4.0">produced</ph>
<ph rev="2.3.0">purge</ph>
<ph rev="2.0.0">range</ph>
rcfile
real
refresh
regexp
rename
<ph rev="IMPALA-5309">repeatable</ph>
replace
<ph rev="2.3.0">restrict</ph>
returns
<ph rev="2.1.0">revoke</ph>
right
rlike
<ph rev="2.1.0">role</ph>
<ph rev="2.1.0">roles</ph>
row
<ph rev="2.0.0">rows</ph>
schema
schemas
select
semi
sequencefile
serdeproperties
<ph rev="2.0.0">serialize_fn</ph>
set
show
smallint
<!-- <ph rev="kudu">split</ph> -->
stats
stored
straight_join
string
symbol
table
tables
<ph rev="2.9.0">tablesample</ph>
tblproperties
terminated
textfile
then
timestamp
tinyint
to
true
<ph rev="2.0.0">truncate</ph>
<ph rev="2.0.0">unbounded</ph>
<ph rev="1.4.0">uncached</ph>
union
<ph rev="kudu">update</ph>
<ph rev="1.2.1">update_fn</ph>
<ph rev="kudu">upsert</ph>
use
using
values
<ph rev="2.0.0">varchar</ph>
view
when
where
with</codeblock>
</conbody>
</concept>

<concept id="reserved_words_planning">
<title>Planning for Future Reserved Words</title>
<conbody>
<p>
The previous list of reserved words includes all the keywords
used in the current level of Impala SQL syntax.
To future-proof your code,
you should avoid additional words in case they
become reserved words if
Impala adds features in later releases.
This kind of planning can also help to avoid
name conflicts in case you port SQL from other systems that
have different sets of reserved words.
</p>

<p>
The following list contains additional words that you should
avoid for table, column, or other object names,
even though they are not currently reserved by Impala.
</p>

<codeblock>any
authorization
backup
begin
break
browse
bulk
cascade
check
checkpoint
close
clustered
coalesce
collate
commit
constraint
contains
continue
convert
current
current_date
current_time
current_timestamp
current_user
cursor
dbcc
deallocate
declare
default
deny
disk
distributed
dump
errlvl
escape
except
exec
execute
exit
fetch
file
fillfactor
for
foreign
freetext
goto
holdlock
identity
index
intersect
key
kill
lineno
merge
national
nocheck
nonclustered
nullif
of
off
offsets
open
option
percent
pivot
plan
precision
primary
print
proc
procedure
public
raiserror
read
readtext
reconfigure
references
replication
restore
restrict
return
revert
rollback
rowcount
rule
save
securityaudit
session_user
setuser
shutdown
some
statistics
system_user
textsize
then
top
tran
transaction
trigger
try_convert
unique
unpivot
updatetext
user
varying
waitfor
while
within
writetext
</codeblock>
</conbody>
</concept>

</concept>