C. SQL 關鍵字

​Table C.1 列出了在 SQL 標準和 PostgreSQL 15.2 中作為關鍵字的所有標記。相關說明提供於第 4.1.1 節中。 （由於篇幅原因，僅收錄了 SQL 標準的最新兩個版本，以及用於歷史對比的 SQL-92，與其他中間標準版本差異較小。）
SQL 區分保留(reserved)關鍵字和非保留(non-reserved)關鍵字。 根據標準，只有保留關鍵字才是真正的關鍵字； 他們永遠不允許作為標識字串。 非保留關鍵字則只在特定的用法中有特殊的含義，而在其他用法中可以作為標識字串使用。 大多數非保留關鍵字實際上是 SQL 指定的內建資料表和函數的名稱。非保留關鍵字的概念本質上只是為了聲明在某些用法中增加了一些預先定義的含義。
在 PostgreSQL 解析器中，情況有點複雜。 有幾種不同類別的標記，從永遠不能用作標識字串的標記，到在解析器中絕對沒有特殊地位，但被視為普通標識字串的標記都有。 （後者通常是 SQL 指定的函數。）即使保留關鍵字在 PostgreSQL 中也沒有完全保留，而是可以用作欄位標籤（例如 SELECT 55 AS CHECK 是可以的，儘管 CHECK 是保留關鍵字） .
在 Table C.1 的 PostgreSQL 欄位中，我們將解析器明確知道但允許作為欄位名稱或資料表名稱的那些關鍵字分類為“non-reserved”。 一些非保留的關鍵字不能用作函數或資料型別名稱，並相應地進行標記。 （這些詞大多表示具有特殊語法的內建函數或資料型別。函數或型別仍然可用，但使用者不能重新定義。）標記為“reserved”的是那些不允許作為欄位或資料表名稱的標記。 允許一些保留關鍵字作為函數或資料型別的名稱； 這也顯示在表格中。 如果沒有這樣標記，保留關鍵字僅允許作為欄位標籤。 此欄中的空白項目表示該關鍵字被 PostgreSQL 視為普通標識字串。
此外，雖然大多數關鍵字可以直接用作欄位標籤而毋須在它們之前使用 AS（如第 7.3.2 節所述），但有一些關鍵詞需要前導 AS 以避免歧義。 在下表中這些關鍵字會標記為“requires AS”。
一般來說，如果使用任何列出的關鍵字作為標識字的命令出現解析錯誤的時候，您應該嘗試將標識字以雙引號括住，再查看問題是否消失。
在研究 Table C.1 之前，重要的是要了解，在 PostgreSQL 中沒有保留關鍵字並不意味著沒有實作與該關鍵字相關的功能。 同樣地，關鍵字的存在也不表示其功能的存在。
Table C.1. SQL Key Words
Key Word
PostgreSQL
SQL:2016
SQL:2011
SQL-92
A
 
non-reserved
non-reserved
 
ABORT
non-reserved
 
 
 
ABS
 
reserved
reserved
 
ABSENT
 
reserved
non-reserved
 
ABSOLUTE
non-reserved
non-reserved
non-reserved
reserved
ACCESS
non-reserved
 
 
 
ACCORDING
 
non-reserved
non-reserved
 
ACOS
 
reserved
 
 
ACTION
non-reserved
non-reserved
non-reserved
reserved
ADA
 
non-reserved
non-reserved
non-reserved
ADD
non-reserved
non-reserved
non-reserved
reserved
ADMIN
non-reserved
non-reserved
non-reserved
 
AFTER
non-reserved
non-reserved
non-reserved
 
AGGREGATE
non-reserved
 
 
 
ALL
reserved
reserved
reserved
reserved
ALLOCATE
 
reserved
reserved
reserved
ALSO
non-reserved
 
 
 
ALTER
non-reserved
reserved
reserved
reserved
ALWAYS
non-reserved
non-reserved
non-reserved
 
ANALYSE
reserved
 
 
 
ANALYZE
reserved
 
 
 
AND
reserved
reserved
reserved
reserved
ANY
reserved
reserved
reserved
reserved
ARE
 
reserved
reserved
reserved
ARRAY
reserved, requires AS
reserved
reserved
 
ARRAY_AGG
 
reserved
reserved
 
ARRAY_​MAX_​CARDINALITY
 
reserved
reserved
 
AS
reserved, requires AS
reserved
reserved
reserved
ASC
reserved
non-reserved
non-reserved
reserved
ASENSITIVE
non-reserved
reserved
reserved
 
ASIN
 
reserved
 
 
ASSERTION
non-reserved
non-reserved
non-reserved
reserved
ASSIGNMENT
non-reserved
non-reserved
non-reserved
 
ASYMMETRIC
reserved
reserved
reserved
 
AT
non-reserved
reserved
reserved
reserved
ATAN
 
reserved
 
 
ATOMIC
non-reserved
reserved
reserved
 
ATTACH
non-reserved
 
 
 
ATTRIBUTE
non-reserved
non-reserved
non-reserved
 
ATTRIBUTES
 
non-reserved
non-reserved
 
AUTHORIZATION
reserved (can be function or type)
reserved
reserved
reserved
AVG
 
reserved
reserved
reserved
BACKWARD
non-reserved
 
 
 
BASE64
 
non-reserved
non-reserved
 
BEFORE
non-reserved
non-reserved
non-reserved
 
BEGIN
non-reserved
reserved
reserved
reserved
BEGIN_FRAME
 
reserved
reserved
 
BEGIN_PARTITION
 
reserved
reserved
 
BERNOULLI
 
non-reserved
non-reserved
 
BETWEEN
non-reserved (cannot be function or type)
reserved
reserved
reserved
BIGINT
non-reserved (cannot be function or type)
reserved
reserved
 
BINARY
reserved (can be function or type)
reserved
reserved
 
BIT
non-reserved (cannot be function or type)
 
 
reserved
BIT_LENGTH
 
 
 
reserved
BLOB
 
reserved
reserved
 
BLOCKED
 
non-reserved
non-reserved
 
BOM
 
non-reserved
non-reserved
 
BOOLEAN
non-reserved (cannot be function or type)
reserved
reserved
 
BOTH
reserved
reserved
reserved
reserved
BREADTH
non-reserved
non-reserved
non-reserved
 
BY
non-reserved
reserved
reserved
reserved
C
 
non-reserved
non-reserved
non-reserved
CACHE
non-reserved
 
 
 
CALL
non-reserved
reserved
reserved
 
CALLED
non-reserved
reserved
reserved
 
CARDINALITY
 
reserved
reserved
 
CASCADE
non-reserved
non-reserved
non-reserved
reserved
CASCADED
non-reserved
reserved
reserved
reserved
CASE
reserved
reserved
reserved
reserved
CAST
reserved
reserved
reserved
reserved
CATALOG
non-reserved
non-reserved
non-reserved
reserved
CATALOG_NAME
 
non-reserved
non-reserved
non-reserved
CEIL
 
reserved
reserved
 
CEILING
 
reserved
reserved
 
CHAIN
non-reserved
non-reserved
non-reserved
 
CHAINING
 
non-reserved
 
 
CHAR
non-reserved (cannot be function or type), requires AS
reserved
reserved
reserved
CHARACTER
non-reserved (cannot be function or type), requires AS
reserved
reserved
reserved
CHARACTERISTICS
non-reserved
non-reserved
non-reserved
 
CHARACTERS
 
non-reserved
non-reserved
 
CHARACTER_LENGTH
 
reserved
reserved
reserved
CHARACTER_​SET_​CATALOG
 
non-reserved
non-reserved
non-reserved
CHARACTER_SET_NAME
 
non-reserved
non-reserved
non-reserved
CHARACTER_SET_SCHEMA
 
non-reserved
non-reserved
non-reserved
CHAR_LENGTH
 
reserved
reserved
reserved
CHECK
reserved
reserved
reserved
reserved
CHECKPOINT
non-reserved
 
 
 
CLASS
non-reserved
 
 
 
CLASSIFIER
 
reserved
 
 
CLASS_ORIGIN
 
non-reserved
non-reserved
non-reserved
CLOB
 
reserved
reserved
 
CLOSE
non-reserved
reserved
reserved
reserved
CLUSTER
non-reserved
 
 
 
COALESCE
non-reserved (cannot be function or type)
reserved
reserved
reserved
COBOL
 
non-reserved
non-reserved
non-reserved
COLLATE
reserved
reserved
reserved
reserved
COLLATION
reserved (can be function or type)
non-reserved
non-reserved
reserved
COLLATION_CATALOG
 
non-reserved
non-reserved
non-reserved
COLLATION_NAME
 
non-reserved
non-reserved
non-reserved
COLLATION_SCHEMA
 
non-reserved
non-reserved
non-reserved
COLLECT
 
reserved
reserved
 
COLUMN
reserved
reserved
reserved
reserved
COLUMNS
non-reserved
non-reserved
non-reserved
 
COLUMN_NAME
 
non-reserved
non-reserved
non-reserved
COMMAND_FUNCTION
 
non-reserved
non-reserved
non-reserved
COMMAND_​FUNCTION_​CODE
 
non-reserved
non-reserved
 
COMMENT
non-reserved
 
 
 
COMMENTS
non-reserved
 
 
 
COMMIT
non-reserved
reserved
reserved
reserved
COMMITTED
non-reserved
non-reserved
non-reserved
non-reserved
COMPRESSION
non-reserved
 
 
 
CONCURRENTLY
reserved (can be function or type)
 
 
 
CONDITION
 
reserved
reserved
 
CONDITIONAL
 
non-reserved
 
 
CONDITION_NUMBER
 
non-reserved
non-reserved
non-reserved
CONFIGURATION
non-reserved
 
 
 
CONFLICT
non-reserved
 
 
 
CONNECT
 
reserved
reserved
reserved
CONNECTION
non-reserved
non-reserved
non-reserved
reserved
CONNECTION_NAME
 
non-reserved
non-reserved
non-reserved
CONSTRAINT
reserved
reserved
reserved
reserved
CONSTRAINTS
non-reserved
non-reserved
non-reserved
reserved
CONSTRAINT_CATALOG
 
non-reserved
non-reserved
non-reserved
CONSTRAINT_NAME
 
non-reserved
non-reserved
non-reserved
CONSTRAINT_SCHEMA
 
non-reserved
non-reserved
non-reserved
CONSTRUCTOR
 
non-reserved
non-reserved
 
CONTAINS
 
reserved
reserved
 
CONTENT
non-reserved
non-reserved
non-reserved
 
CONTINUE
non-reserved
non-reserved
non-reserved
reserved
CONTROL
 
non-reserved
non-reserved
 
CONVERSION
non-reserved
 
 
 
CONVERT
 
reserved
reserved
reserved
COPY
non-reserved
reserved
 
 
CORR
 
reserved
reserved
 
CORRESPONDING
 
reserved
reserved
reserved
COS
 
reserved
 
 
COSH
 
reserved
 
 
COST
non-reserved
 
 
 
COUNT
 
reserved
reserved
reserved
COVAR_POP
 
reserved
reserved
 
COVAR_SAMP
 
reserved
reserved
 
CREATE
reserved, requires AS
reserved
reserved

Key Word	PostgreSQL	SQL:2016	SQL:2011	SQL-92
`A`		non-reserved	non-reserved
`ABORT`	non-reserved
`ABS`		reserved	reserved
`ABSENT`		reserved	non-reserved
`ABSOLUTE`	non-reserved	non-reserved	non-reserved	reserved
`ACCESS`	non-reserved
`ACCORDING`		non-reserved	non-reserved
`ACOS`		reserved
`ACTION`	non-reserved	non-reserved	non-reserved	reserved
`ADA`		non-reserved	non-reserved	non-reserved
`ADD`	non-reserved	non-reserved	non-reserved	reserved
`ADMIN`	non-reserved	non-reserved	non-reserved
`AFTER`	non-reserved	non-reserved	non-reserved
`AGGREGATE`	non-reserved
`ALL`	reserved	reserved	reserved	reserved
`ALLOCATE`		reserved	reserved	reserved
`ALSO`	non-reserved
`ALTER`	non-reserved	reserved	reserved	reserved
`ALWAYS`	non-reserved	non-reserved	non-reserved
`ANALYSE`	reserved
`ANALYZE`	reserved
`AND`	reserved	reserved	reserved	reserved
`ANY`	reserved	reserved	reserved	reserved
`ARE`		reserved	reserved	reserved
`ARRAY`	reserved, requires `AS`	reserved	reserved
`ARRAY_AGG`		reserved	reserved
`ARRAY_MAX_CARDINALITY`		reserved	reserved
`AS`	reserved, requires `AS`	reserved	reserved	reserved
`ASC`	reserved	non-reserved	non-reserved	reserved
`ASENSITIVE`	non-reserved	reserved	reserved
`ASIN`		reserved
`ASSERTION`	non-reserved	non-reserved	non-reserved	reserved
`ASSIGNMENT`	non-reserved	non-reserved	non-reserved
`ASYMMETRIC`	reserved	reserved	reserved
`AT`	non-reserved	reserved	reserved	reserved
`ATAN`		reserved
`ATOMIC`	non-reserved	reserved	reserved
`ATTACH`	non-reserved
`ATTRIBUTE`	non-reserved	non-reserved	non-reserved
`ATTRIBUTES`		non-reserved	non-reserved
`AUTHORIZATION`	reserved (can be function or type)	reserved	reserved	reserved
`AVG`		reserved	reserved	reserved
`BACKWARD`	non-reserved
`BASE64`		non-reserved	non-reserved
`BEFORE`	non-reserved	non-reserved	non-reserved
`BEGIN`	non-reserved	reserved	reserved	reserved
`BEGIN_FRAME`		reserved	reserved
`BEGIN_PARTITION`		reserved	reserved
`BERNOULLI`		non-reserved	non-reserved
`BETWEEN`	non-reserved (cannot be function or type)	reserved	reserved	reserved
`BIGINT`	non-reserved (cannot be function or type)	reserved	reserved
`BINARY`	reserved (can be function or type)	reserved	reserved
`BIT`	non-reserved (cannot be function or type)			reserved
`BIT_LENGTH`				reserved
`BLOB`		reserved	reserved
`BLOCKED`		non-reserved	non-reserved
`BOM`		non-reserved	non-reserved
`BOOLEAN`	non-reserved (cannot be function or type)	reserved	reserved
`BOTH`	reserved	reserved	reserved	reserved
`BREADTH`	non-reserved	non-reserved	non-reserved
`BY`	non-reserved	reserved	reserved	reserved
`C`		non-reserved	non-reserved	non-reserved
`CACHE`	non-reserved
`CALL`	non-reserved	reserved	reserved
`CALLED`	non-reserved	reserved	reserved
`CARDINALITY`		reserved	reserved
`CASCADE`	non-reserved	non-reserved	non-reserved	reserved
`CASCADED`	non-reserved	reserved	reserved	reserved
`CASE`	reserved	reserved	reserved	reserved
`CAST`	reserved	reserved	reserved	reserved
`CATALOG`	non-reserved	non-reserved	non-reserved	reserved
`CATALOG_NAME`		non-reserved	non-reserved	non-reserved
`CEIL`		reserved	reserved
`CEILING`		reserved	reserved
`CHAIN`	non-reserved	non-reserved	non-reserved
`CHAINING`		non-reserved
`CHAR`	non-reserved (cannot be function or type), requires `AS`	reserved	reserved	reserved
`CHARACTER`	non-reserved (cannot be function or type), requires `AS`	reserved	reserved	reserved
`CHARACTERISTICS`	non-reserved	non-reserved	non-reserved
`CHARACTERS`		non-reserved	non-reserved
`CHARACTER_LENGTH`		reserved	reserved	reserved
`CHARACTER_SET_CATALOG`		non-reserved	non-reserved	non-reserved
`CHARACTER_SET_NAME`		non-reserved	non-reserved	non-reserved
`CHARACTER_SET_SCHEMA`		non-reserved	non-reserved	non-reserved
`CHAR_LENGTH`		reserved	reserved	reserved
`CHECK`	reserved	reserved	reserved	reserved
`CHECKPOINT`	non-reserved
`CLASS`	non-reserved
`CLASSIFIER`		reserved
`CLASS_ORIGIN`		non-reserved	non-reserved	non-reserved
`CLOB`		reserved	reserved
`CLOSE`	non-reserved	reserved	reserved	reserved
`CLUSTER`	non-reserved
`COALESCE`	non-reserved (cannot be function or type)	reserved	reserved	reserved
`COBOL`		non-reserved	non-reserved	non-reserved
`COLLATE`	reserved	reserved	reserved	reserved
`COLLATION`	reserved (can be function or type)	non-reserved	non-reserved	reserved
`COLLATION_CATALOG`		non-reserved	non-reserved	non-reserved
`COLLATION_NAME`		non-reserved	non-reserved	non-reserved
`COLLATION_SCHEMA`		non-reserved	non-reserved	non-reserved
`COLLECT`		reserved	reserved
`COLUMN`	reserved	reserved	reserved	reserved
`COLUMNS`	non-reserved	non-reserved	non-reserved
`COLUMN_NAME`		non-reserved	non-reserved	non-reserved
`COMMAND_FUNCTION`		non-reserved	non-reserved	non-reserved
`COMMAND_FUNCTION_CODE`		non-reserved	non-reserved
`COMMENT`	non-reserved
`COMMENTS`	non-reserved
`COMMIT`	non-reserved	reserved	reserved	reserved
`COMMITTED`	non-reserved	non-reserved	non-reserved	non-reserved
`COMPRESSION`	non-reserved
`CONCURRENTLY`	reserved (can be function or type)
`CONDITION`		reserved	reserved
`CONDITIONAL`		non-reserved
`CONDITION_NUMBER`		non-reserved	non-reserved	non-reserved
`CONFIGURATION`	non-reserved
`CONFLICT`	non-reserved
`CONNECT`		reserved	reserved	reserved
`CONNECTION`	non-reserved	non-reserved	non-reserved	reserved
`CONNECTION_NAME`		non-reserved	non-reserved	non-reserved
`CONSTRAINT`	reserved	reserved	reserved	reserved
`CONSTRAINTS`	non-reserved	non-reserved	non-reserved	reserved
`CONSTRAINT_CATALOG`		non-reserved	non-reserved	non-reserved
`CONSTRAINT_NAME`		non-reserved	non-reserved	non-reserved
`CONSTRAINT_SCHEMA`		non-reserved	non-reserved	non-reserved
`CONSTRUCTOR`		non-reserved	non-reserved
`CONTAINS`		reserved	reserved
`CONTENT`	non-reserved	non-reserved	non-reserved
`CONTINUE`	non-reserved	non-reserved	non-reserved	reserved
`CONTROL`		non-reserved	non-reserved
`CONVERSION`	non-reserved
`CONVERT`		reserved	reserved	reserved
`COPY`	non-reserved	reserved
`CORR`		reserved	reserved
`CORRESPONDING`		reserved	reserved	reserved
`COS`		reserved
`COSH`		reserved
`COST`	non-reserved
`COUNT`		reserved	reserved	reserved
`COVAR_POP`		reserved	reserved
`COVAR_SAMP`		reserved	reserved
`CREATE`	reserved, requires `AS`	reserved	reserved