C. SQL 關鍵字

Table C.1 lists all tokens that are key words in the SQL standard and in PostgreSQL 11devel. Background information can be found in Section 4.1.1. (For space reasons, only the latest two versions of the SQL standard, and SQL-92 for historical comparison, are included. The differences between those and the other intermediate standard versions are small.)

SQL distinguishes between reserved and non-reserved key words. According to the standard, reserved key words are the only real key words; they are never allowed as identifiers. Non-reserved key words only have a special meaning in particular contexts and can be used as identifiers in other contexts. Most non-reserved key words are actually the names of built-in tables and functions specified by SQL. The concept of non-reserved key words essentially only exists to declare that some predefined meaning is attached to a word in some contexts.

In the PostgreSQL parser life is a bit more complicated. There are several different classes of tokens ranging from those that can never be used as an identifier to those that have absolutely no special status in the parser as compared to an ordinary identifier. (The latter is usually the case for functions specified by SQL.) Even reserved key words are not completely reserved in PostgreSQL, but can be used as column labels (for example, SELECT 55 AS CHECK, even though CHECK is a reserved key word).

In Table C.1 in the column for PostgreSQL we classify as “non-reserved” those key words that are explicitly known to the parser but are allowed as column or table names. Some key words that are otherwise non-reserved cannot be used as function or data type names and are marked accordingly. (Most of these words represent built-in functions or data types with special syntax. The function or type is still available but it cannot be redefined by the user.) Labeled “reserved” are those tokens that are not allowed as column or table names. Some reserved key words are allowable as names for functions or data types; this is also shown in the table. If not so marked, a reserved key word is only allowed as an “AS” column label name.

As a general rule, if you get spurious parser errors for commands that contain any of the listed key words as an identifier you should try to quote the identifier to see if the problem goes away.

It is important to understand before studying Table C.1 that the fact that a key word is not reserved in PostgreSQL does not mean that the feature related to the word is not implemented. Conversely, the presence of a key word does not indicate the existence of a feature.

Table C.1. SQL Key Words

Key Word

PostgreSQL

SQL:2011

SQL:2008

SQL-92

A

non-reserved

ABORT

non-reserved

ABS

reserved

ABSENT

non-reserved

ABSOLUTE

non-reserved

reserved

ACCESS

non-reserved

ACCORDING

non-reserved

ACTION

non-reserved

reserved

ADA

non-reserved

ADD

non-reserved

reserved

ADMIN

non-reserved

AFTER

non-reserved

AGGREGATE

non-reserved

ALL

reserved

ALLOCATE

reserved

ALSO

non-reserved

ALTER

non-reserved

reserved

ALWAYS

non-reserved

ANALYSE

reserved

ANALYZE

reserved

AND

reserved

ANY

reserved

ARE

reserved

ARRAY

reserved

ARRAY_AGG

reserved

ARRAY_MAX_CARDINALITY

reserved

AS

reserved

ASC

reserved

non-reserved

reserved

ASENSITIVE

reserved

ASSERTION

non-reserved

reserved

ASSIGNMENT

non-reserved

ASYMMETRIC

reserved

AT

non-reserved

reserved

ATOMIC

reserved

ATTACH

non-reserved

ATTRIBUTE

non-reserved

ATTRIBUTES

non-reserved

AUTHORIZATION

reserved (can be function or type)

reserved

AVG

reserved

BACKWARD

non-reserved

BASE64

non-reserved

BEFORE

non-reserved

BEGIN

non-reserved

reserved

BEGIN_FRAME

reserved

BEGIN_PARTITION

reserved

BERNOULLI

non-reserved

BETWEEN

non-reserved (cannot be function or type)

reserved

BIGINT

non-reserved (cannot be function or type)

reserved

BINARY

reserved (can be function or type)

reserved

BIT

non-reserved (cannot be function or type)

reserved

BIT_LENGTH

reserved

BLOB

reserved

BLOCKED

non-reserved

BOM

non-reserved

BOOLEAN

non-reserved (cannot be function or type)

reserved

BOTH

reserved

BREADTH

non-reserved

BY

non-reserved

reserved

C

non-reserved

CACHE

non-reserved

CALL

reserved

CALLED

non-reserved

reserved

CARDINALITY

reserved

CASCADE

non-reserved

reserved

CASCADED

non-reserved

reserved

CASE

reserved

CAST

reserved

CATALOG

non-reserved

reserved

CATALOG_NAME

non-reserved

CEIL

reserved

CEILING

reserved

CHAIN

non-reserved

CHAR

non-reserved (cannot be function or type)

reserved

CHARACTER

non-reserved (cannot be function or type)

reserved

CHARACTERISTICS

non-reserved

CHARACTERS

non-reserved

CHARACTER_LENGTH

reserved

CHARACTER_SET_CATALOG

non-reserved

CHARACTER_SET_NAME

non-reserved

CHARACTER_SET_SCHEMA

non-reserved

CHAR_LENGTH

reserved

CHECK

reserved

CHECKPOINT

non-reserved

CLASS

non-reserved

CLASS_ORIGIN

non-reserved

CLOB

reserved

CLOSE

non-reserved

reserved

CLUSTER

non-reserved

COALESCE

non-reserved (cannot be function or type)

reserved

COBOL

non-reserved

COLLATE

reserved

COLLATION

reserved (can be function or type)

non-reserved

reserved

COLLATION_CATALOG

non-reserved

COLLATION_NAME

non-reserved

COLLATION_SCHEMA

non-reserved

COLLECT

reserved

COLUMN

reserved

COLUMNS

non-reserved

COLUMN_NAME

non-reserved

COMMAND_FUNCTION

non-reserved

COMMAND_FUNCTION_CODE

non-reserved

COMMENT

non-reserved

COMMENTS

non-reserved

COMMIT

non-reserved

reserved

COMMITTED

non-reserved

CONCURRENTLY

reserved (can be function or type)

CONDITION

reserved

CONDITION_NUMBER

non-reserved

CONFIGURATION

non-reserved

CONFLICT

non-reserved

CONNECT

reserved

CONNECTION

non-reserved

reserved

CONNECTION_NAME

non-reserved

CONSTRAINT

reserved

CONSTRAINTS

non-reserved

reserved

CONSTRAINT_CATALOG

non-reserved

CONSTRAINT_NAME

non-reserved

CONSTRAINT_SCHEMA

non-reserved

CONSTRUCTOR

non-reserved

CONTAINS

reserved

non-reserved

CONTENT

non-reserved

CONTINUE

non-reserved

reserved

CONTROL

non-reserved

CONVERSION

non-reserved

CONVERT

reserved

COPY

non-reserved

CORR

reserved

CORRESPONDING

reserved

COST

non-reserved

COUNT

reserved

COVAR_POP

reserved

COVAR_SAMP

reserved

CREATE

reserved

CROSS

reserved (can be function or type)

reserved

CSV

non-reserved

CUBE

non-reserved

reserved

CUME_DIST

reserved

CURRENT

non-reserved

reserved

CURRENT_CATALOG

reserved

CURRENT_DATE

reserved

CURRENT_DEFAULT_TRANSFORM_GROUP

reserved

CURRENT_PATH

reserved

CURRENT_ROLE

reserved

CURRENT_ROW

reserved

CURRENT_SCHEMA

reserved (can be function or type)

reserved

CURRENT_TIME

reserved

CURRENT_TIMESTAMP

reserved

CURRENT_TRANSFORM_GROUP_FOR_TYPE

reserved

CURRENT_USER

reserved

CURSOR

non-reserved

reserved

CURSOR_NAME

non-reserved

CYCLE

non-reserved

reserved

DATA

non-reserved

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