数据库 关键字一览表(数据库关键字有哪些)

推荐整理分享数据库 关键字一览表(数据库关键字有哪些)，希望有所帮助，仅作参考，欢迎阅读内容。

文章相关热门搜索词:数据库关键字和主键,数据库关键字段,数据库关键字,数据库关键字,数据库关键字desc表示什么,数据库关键字名词解释,数据库关键字是什么,数据库关键字desc表示什么,内容如对您有帮助，希望把文章链接给更多的朋友！

数据库 关键字：

为了避免在数据库表结构设计过程中使用系统保留关键字我们必须知道数据库存在哪些关键字，接下来会列出mysql、oracle、sqlserver三个数据库各自的保留关键字。

Mysql

ACCESSIBLE (R) ACCOUNT[a] ACTION ADD (R) AFTER AGAINST AGGREGATE ALGORITHM ALL (R) ALTER (R) ALWAYS[b] ANALYSE ANALYZE (R) AND (R) ANY AS (R) ASC (R) ASCII ASENSITIVE (R) AT AUTOEXTEND_SIZE AUTO_INCREMENT AVG AVG_ROW_LENGTH BACKUP BEFORE (R) BEGIN BETWEEN (R) BIGINT (R) BINARY (R) BINLOG BIT BLOB (R) BLOCK BOOL BOOLEAN BOTH (R) BTREE BY (R) BYTE CACHE CALL (R) CASCADE (R) CASCADED CASE (R) CATALOG_NAME CHAIN CHANGE (R) CHANGED CHANNEL[c] CHAR (R) CHARACTER (R) CHARSET CHECK (R) CHECKSUM CIPHER CLASS_ORIGIN CLIENT CLOSE COALESCE CODE COLLATE (R) COLLATION COLUMN (R) COLUMNS COLUMN_FORMAT COLUMN_NAME COMMENT COMMIT COMMITTED COMPACT COMPLETION COMPRESSED COMPRESSION[d] CONCURRENT CONDITION (R) CONNECTION CONSISTENT CONSTRAINT (R) CONSTRAINT_CATALOG CONSTRAINT_NAME CONSTRAINT_SCHEMA CONTAINS CONTEXT CONTINUE (R) CONVERT (R) CPU CREATE (R) CROSS (R) CUBE CURRENT CURRENT_DATE (R) CURRENT_TIME (R) CURRENT_TIMESTAMP (R) CURRENT_USER (R) CURSOR (R) CURSOR_NAME DATA DATABASE (R) DATABASES (R) DATAFILE DATE DATETIME DAY DAY_HOUR (R) DAY_MICROSECOND (R) DAY_MINUTE (R) DAY_SECOND (R) DEALLOCATE DEC (R) DECIMAL (R) DECLARE (R) DEFAULT (R) DEFAULT_AUTH DEFINER DELAYED (R) DELAY_KEY_WRITE DELETE (R) DESC (R) DESCRIBE (R) DES_KEY_FILE DETERMINISTIC (R) DIAGNOSTICS DIRECTORY DISABLE DISCARD DISK DISTINCT (R) DISTINCTROW (R) DIV (R) DO DOUBLE (R) DROP (R) DUAL (R) DUMPFILE DUPLICATE DYNAMIC EACH (R) ELSE (R) ELSEIF (R) ENABLE ENCLOSED (R) ENCRYPTION[e] END ENDS ENGINE ENGINES ENUM ERROR ERRORS ESCAPE ESCAPED (R) EVENT EVENTS EVERY EXCHANGE EXECUTE EXISTS (R) EXIT (R) EXPANSION EXPIRE EXPLAIN (R) EXPORT EXTENDED EXTENT_SIZE FALSE (R) FAST FAULTS FETCH (R) FIELDS FILE FILE_BLOCK_SIZE[f] FILTER[g] FIRST FIXED FLOAT (R) FLOAT4 (R) FLOAT8 (R) FLUSH FOLLOWS[h] FOR (R) FORCE (R) FOREIGN (R) FORMAT FOUND FROM (R) FULL FULLTEXT (R) FUNCTION GENERAL GENERATED[i] (R) GEOMETRY GEOMETRYCOLLECTION GET (R) GET_FORMAT GLOBAL GRANT (R) GRANTS GROUP (R) GROUP_REPLICATION[j] HANDLER HASH HAVING (R) HELP HIGH_PRIORITY (R) HOST HOSTS HOUR HOUR_MICROSECOND (R) HOUR_MINUTE (R) HOUR_SECOND (R) IDENTIFIED IF (R) IGNORE (R) IGNORE_SERVER_IDS IMPORT IN (R) INDEX (R) INDEXES INFILE (R) INITIAL_SIZE INNER (R) INOUT (R) INSENSITIVE (R) INSERT (R) INSERT_METHOD INSTALL INSTANCE[k] INT (R) INT1 (R) INT2 (R) INT3 (R) INT4 (R) INT8 (R) INTEGER (R) INTERVAL (R) INTO (R) INVOKER IO IO_AFTER_GTIDS (R) IO_BEFORE_GTIDS (R) IO_THREAD IPC IS (R) ISOLATION ISSUER ITERATE (R) JOIN (R) JSON[l] KEY (R) KEYS (R) KEY_BLOCK_SIZE KILL (R) LANGUAGE LAST LEADING (R) LEAVE (R) LEAVES LEFT (R) LESS LEVEL LIKE (R) LIMIT (R) LINEAR (R) LINES (R) LINESTRING LIST LOAD (R) LOCAL LOCALTIME (R) LOCALTIMESTAMP (R) LOCK (R) LOCKS LOGFILE LOGS LONG (R) LONGBLOB (R) LONGTEXT (R) LOOP (R) LOW_PRIORITY (R) MASTER MASTER_AUTO_POSITION MASTER_BIND (R) MASTER_CONNECT_RETRY MASTER_DELAY MASTER_HEARTBEAT_PERIOD MASTER_HOST MASTER_LOG_FILE MASTER_LOG_POS MASTER_PASSWORD MASTER_PORT MASTER_RETRY_COUNT MASTER_SERVER_ID MASTER_SSL MASTER_SSL_CA MASTER_SSL_CAPATH MASTER_SSL_CERT MASTER_SSL_CIPHER MASTER_SSL_CRL MASTER_SSL_CRLPATH MASTER_SSL_KEY MASTER_SSL_VERIFY_SERVER_CERT (R) MASTER_TLS_VERSION[m] MASTER_USER MATCH (R) MAXVALUE (R) MAX_CONNECTIONS_PER_HOUR MAX_QUERIES_PER_HOUR MAX_ROWS MAX_SIZE MAX_STATEMENT_TIME[n] MAX_UPDATES_PER_HOUR MAX_USER_CONNECTIONS MEDIUM MEDIUMBLOB (R) MEDIUMINT (R) MEDIUMTEXT (R) MEMORY MERGE MESSAGE_TEXT MICROSECOND MIDDLEINT (R) MIGRATE MINUTE MINUTE_MICROSECOND (R) MINUTE_SECOND (R) MIN_ROWS MOD (R) MODE MODIFIES (R) MODIFY MONTH MULTILINESTRING MULTIPOINT MULTIPOLYGON MUTEX MYSQL_ERRNO NAME NAMES NATIONAL NATURAL (R) NCHAR NDB NDBCLUSTER NEVER[o] NEW NEXT NO NODEGROUP NONBLOCKING[p] NONE NOT (R) NO_WAIT NO_WRITE_TO_BINLOG (R) NULL (R) NUMBER NUMERIC (R) NVARCHAR OFFSET OLD_PASSWORD[q] ON (R) ONE ONLY OPEN OPTIMIZE (R) OPTIMIZER_COSTS[r] (R) OPTION (R) OPTIONALLY (R) OPTIONS OR (R) ORDER (R) OUT (R) OUTER (R) OUTFILE (R) OWNER PACK_KEYS PAGE PARSER PARSE_GCOL_EXPR[s] PARTIAL PARTITION (R) PARTITIONING PARTITIONS PASSWORD PHASE PLUGIN PLUGINS PLUGIN_DIR POINT POLYGON PORT PRECEDES[t] PRECISION (R) PREPARE PRESERVE PREV PRIMARY (R) PRIVILEGES PROCEDURE (R) PROCESSLIST PROFILE PROFILES PROXY PURGE (R) QUARTER QUERY QUICK RANGE (R) READ (R) READS (R) READ_ONLY READ_WRITE (R) REAL (R) REBUILD RECOVER REDOFILE REDO_BUFFER_SIZE REDUNDANT REFERENCES (R) REGEXP (R) RELAY RELAYLOG RELAY_LOG_FILE RELAY_LOG_POS RELAY_THREAD RELEASE (R) RELOAD REMOVE RENAME (R) REORGANIZE REPAIR REPEAT (R) REPEATABLE REPLACE (R) REPLICATE_DO_DB[u] REPLICATE_DO_TABLE[v] REPLICATE_IGNORE_DB[w] REPLICATE_IGNORE_TABLE[x] REPLICATE_REWRITE_DB[y] REPLICATE_WILD_DO_TABLE[z] REPLICATE_WILD_IGNORE_TABLE[aa] REPLICATION REQUIRE (R) RESET RESIGNAL (R) RESTORE RESTRICT (R) RESUME RETURN (R) RETURNED_SQLSTATE RETURNS REVERSE REVOKE (R) RIGHT (R) RLIKE (R) ROLLBACK ROLLUP ROTATE[ab] ROUTINE ROW ROWS ROW_COUNT ROW_FORMAT RTREE SAVEPOINT SCHEDULE SCHEMA (R) SCHEMAS (R) SCHEMA_NAME SECOND SECOND_MICROSECOND (R) SECURITY SELECT (R) SENSITIVE (R) SEPARATOR (R) SERIAL SERIALIZABLE SERVER SESSION SET (R) SHARE SHOW (R) SHUTDOWN SIGNAL (R) SIGNED SIMPLE SLAVE SLOW SMALLINT (R) SNAPSHOT SOCKET SOME SONAME SOUNDS SOURCE SPATIAL (R) SPECIFIC (R) SQL (R) SQLEXCEPTION (R) SQLSTATE (R) SQLWARNING (R) SQL_AFTER_GTIDS SQL_AFTER_MTS_GAPS SQL_BEFORE_GTIDS SQL_BIG_RESULT (R) SQL_BUFFER_RESULT SQL_CACHE SQL_CALC_FOUND_ROWS (R) SQL_NO_CACHE SQL_SMALL_RESULT (R) SQL_THREAD SQL_TSI_DAY SQL_TSI_HOUR SQL_TSI_MINUTE SQL_TSI_MONTH SQL_TSI_QUARTER SQL_TSI_SECOND SQL_TSI_WEEK SQL_TSI_YEAR SSL (R) STACKED START STARTING (R) STARTS STATS_AUTO_RECALC STATS_PERSISTENT STATS_SAMPLE_PAGES STATUS STOP STORAGE STORED[ac] (R) STRAIGHT_JOIN (R) STRING SUBCLASS_ORIGIN SUBJECT SUBPARTITION SUBPARTITIONS SUPER SUSPEND SWAPS SWITCHES TABLE (R) TABLES TABLESPACE TABLE_CHECKSUM TABLE_NAME TEMPORARY TEMPTABLE TERMINATED (R) TEXT THAN THEN (R) TIME TIMESTAMP TIMESTAMPADD TIMESTAMPDIFF TINYBLOB (R) TINYINT (R) TINYTEXT (R) TO (R) TRAILING (R) TRANSACTION TRIGGER (R) TRIGGERS TRUE (R) TRUNCATE TYPE TYPES UNCOMMITTED UNDEFINED UNDO (R) UNDOFILE UNDO_BUFFER_SIZE UNICODE UNINSTALL UNION (R) UNIQUE (R) UNKNOWN UNLOCK (R) UNSIGNED (R) UNTIL UPDATE (R) UPGRADE USAGE (R) USE (R) USER USER_RESOURCES USE_FRM USING (R) UTC_DATE (R) UTC_TIME (R) UTC_TIMESTAMP (R) VALIDATION[ad] VALUE VALUES (R) VARBINARY (R) VARCHAR (R) VARCHARACTER (R) VARIABLES VARYING (R) VIEW VIRTUAL[ae] (R) WAIT WARNINGS WEEK WEIGHT_STRING WHEN (R) WHERE (R) WHILE (R) WITH (R) WITHOUT[af] WORK WRAPPER WRITE (R) X XA XID[ag] XML XOR (R) YEAR YEAR_MONTH (R) ZEROFILL (R)

Oracle

select * from v$reserved_words order by keyword asc

SQLServer

SQL Server 保留关键字。

add

EXTERNAL

PROCEDURE

ALL

FETCH

PUBLIC

ALTER

FILE

RAISERROR

And

FILLFACTOR

READ

ANY

FOR

READTEXT

As

FOREIGN

RECONFIGURE

ASC

FREETEXT

REFERENCES

AUTHORIZATION

FREETEXTTABLE

REPLICATION

BACKUP

from

RESTORE

BEGIN

FULL

RESTRICT

BETWEEN

FUNCTION

RETURN

BREAK

GOTO

REVERT

BROWSE

GRANT

REVOKE

BULK

GROUP

RIGHT

BY

HAVING

ROLLBACK

CASCADE

HOLDLOCK

ROWCOUNT

Case

IDENTITY

ROWGUIDCOL

CHECK

IDENTITY_INSERT

RULE

CHECKPOINT

IDENTITYCOL

SAVE

close

IF

SCHEMA

CLUSTERED

IN

SECURITYAUDIT

COALESCE

INDEX

SELECT

COLLATE

INNER

SEMANTICKEYPHRASETABLE

COLUMN

INSERT

SEMANTICSIMILARITYDETAILSTABLE

COMMIT

INTERSECT

SEMANTICSIMILARITYTABLE

COMPUTE

INTO

SESSION_USER

CONSTRAINT

is

SET

CONTAINS

JOIN

SETUSER

CONTAINSTABLE

KEY

SHUTDOWN

CONTINUE

KILL

SOME

CONVERT

LEFT

STATISTICS

CREATE

LIKE

SYSTEM_USER

CROSS

LINENO

TABLE

CURRENT

LOAD

TABLESAMPLE

CURRENT_DATE

MERGE

TEXTSIZE

CURRENT_TIME

NATIONAL

THEN

CURRENT_TIMESTAMP

NOCHECK

目标

CURRENT_USER

NONCLUSTERED

TOP

CURSOR

NOT

TRAN

DATABASE

NULL

TRANSACTION

DBCC

NULLIF

Trigger

DEALLOCATE

OF

TRUNCATE

DECLARE

OFF

TRY_CONVERT

DEFAULT

OFFSETS

TSEQUAL

delete

ON

UNION

DENY

OPEN

UNIQUE

DESC

OPENDATASOURCE

UNPIVOT

DISK

OPENQUERY

UPDATE

DISTINCT

OPENROWSET

UPDATETEXT

DISTRIBUTED

OPENXML

USE

DOUBLE

OPTION

USER

DROP

OR

VALUES

DUMP

ORDER

VARYING

Else

OUTER

View

END

OVER

WAITFOR

ERRLVL

PERCENT

WHEN

ESCAPE

PIVOT

WHERE

EXCEPT

PLAN

WHILE

EXEC

PRECISION

WITH

EXECUTE

PRIMARY

WITHIN GROUP

EXISTS

PRINT

WRITETEXT

EXIT

PROC

此外，ISO 标准定义了保留关键字列表。 不要使用 ISO 保留关键字作为对象名和标识符。 ODBC 保留关键字列表（如下表所示）与 ISO 保留关键字列表相同。

注意

ISO 标准保留关键字有时可能比 SQL Server 限制更多，有时则更少。 例如，ISO 保留关键字列表包含 INT。 SQL Server 不必将此区分为保留关键字。

Transact-SQL 保留关键字可用作数据库或数据库对象（如表、列、视图等）的标识符或名称。 使用带引号的标识符或分隔标识符。 不限制将保留关键字用作变量和存储过程参数的名

ODBC 保留关键字

保留了下列关键字以用于 ODBC 函数调用。这些关键字根本不约束 SQL 语法；然而，为确保与支持核心 SQL 语法的驱动程序兼容，应用程序应避免使用这些关键字。

下面是当前的 ODBC 保留关键字列表。

ABSOLUTE

EXEC

OVERLAPS

ACTION

EXECUTE

PAD

ADA

EXISTS

PARTIAL

ADD

EXTERNAL

PASCAL

ALL

EXTRACT

POSITION

ALLOCATE

FALSE

PRECISION

ALTER

FETCH

PREPARE

AND

FIRST

PRESERVE

ANY

FLOAT

PRIMARY

ARE

FOR

PRIOR

AS

FOREIGN

PRIVILEGES

ASC

FORTRAN

PROCEDURE

ASSERTION

FOUND

PUBLIC

AT

FROM

READ

AUTHORIZATION

FULL

REAL

AVG

GET

REFERENCES

BEGIN

GLOBAL

RELATIVE

BETWEEN

GO

RESTRICT

BIT

GOTO

REVOKE

BIT_LENGTH

GRANT

RIGHT

BOTH

GROUP

ROLLBACK

BY

HAVING

ROWS

CASCADE

HOUR

SCHEMA

CASCADED

IDENTITY

SCROLL

CASE

IMMEDIATE

SECOND

CAST

IN

SECTION

CATALOG

INCLUDE

SELECT

CHAR

INDEX

SESSION

CHAR_LENGTH

INDICATOR

SESSION_USER

CHARACTER

INITIALLY

SET

CHARACTER_LENGTH

INNER

SIZE

CHECK

INPUT

SMALLINT

CLOSE

INSENSITIVE

SOME

COALESCE

INSERT

SPACE

COLLATE

INT

SQL

COLLATION

INTEGER

SQLCA

COLUMN

INTERSECT

SQLCODE

COMMIT

INTERVAL

SQLERROR

CONNECT

INTO

SQLSTATE

CONNECTION

IS

SQLWARNING

CONSTRAINT

ISOLATION

SUBSTRING

CONSTRAINTS

JOIN

SUM

CONTINUE

KEY

SYSTEM_USER

CONVERT

LANGUAGE

TABLE

CORRESPONDING

LAST

TEMPORARY

COUNT

LEADING

THEN

CREATE

LEFT

TIME

CROSS

LEVEL

TIMESTAMP

CURRENT

LIKE

TIMEZONE_HOUR

CURRENT_DATE

LOCAL

TIMEZONE_MINUTE

CURRENT_TIME

LOWER

TO

CURRENT_TIMESTAMP

MATCH

TRAILING

CURRENT_USER

MAX

TRANSACTION

CURSOR

MIN

TRANSLATE

DATE

MINUTE

TRANSLATION

DAY

MODULE

TRIM

DEALLOCATE

MONTH

TRUE

DEC

NAMES

UNION

DECIMAL

NATIONAL

UNIQUE

DECLARE

NATURAL

UNKNOWN

DEFAULT

NCHAR

UPDATE

DEFERRABLE

NEXT

UPPER

DEFERRED

NO

USAGE

DELETE

NONE

USER

DESC

NOT

USING

DESCRIBE

NULL

VALUE

DESCRIPTOR

NULLIF

VALUES

DIAGNOSTICS

NUMERIC

VARCHAR

DISCONNECT

OCTET_LENGTH

VARYING

DISTINCT

OF

VIEW

DOMAIN

ON

WHEN

DOUBLE

ONLY

WHENEVER

DROP

OPEN

WHERE

ELSE

OPTION

WITH

END

OR

WORK

END-EXEC

ORDER

WRITE

ESCAPE

OUTER

YEAR

EXCEPT

OUTPUT

ZONE

EXCEPTION

将来的关键字

下列关键字可能会在将来的 SQL Server 版本中保留使用，作为将来要实现的新功能。注意，不要使用这些关键字作为标识符。

ABSOLUTE

HOST

RELATIVE

ACTION

HOUR

RELEASE

ADMIN

IGNORE

RESULT

AFTER

IMMEDIATE

RETURNS

AGGREGATE

INDICATOR

ROLE

ALIAS

INITIALIZE

ROLLUP

ALLOCATE

INITIALLY

ROUTINE

ARE

INOUT

ROW

ARRAY

INPUT

ROWS

ASENSITIVE

INT

SAVEPOINT

ASSERTION

INTEGER

SCROLL

ASYMMETRIC

INTERSECTION

SCOPE

AT

INTERVAL

SEARCH

ATOMIC

ISOLATION

SECOND

BEFORE

ITERATE

SECTION

BINARY

LANGUAGE

SENSITIVE

BIT

LARGE

SEQUENCE

BLOB

LAST

SESSION

BOOLEAN

LATERAL

SETS

BOTH

LEADING

SIMILAR

BREADTH

LESS

SIZE

CALL

LEVEL

SMALLINT

CALLED

LIKE_REGEX

SPACE

CARDINALITY

LIMIT

SPECIFIC

CASCADED

LN

SPECIFICTYPE

CAST

LOCAL

SQL

CATALOG

LOCALTIME

SQLEXCEPTION

CHAR

LOCALTIMESTAMP

SQLSTATE

CHARACTER

LOCATOR

SQLWARNING

CLASS

MAP

START

CLOB

MATCH

STATE

COLLATION

MEMBER

STATEMENT

COLLECT

METHOD

STATIC

COMPLETION

MINUTE

STDDEV_POP

CONDITION

MOD

STDDEV_SAMP

CONNECT

MODIFIES

STRUCTURE

CONNECTION

MODIFY

SUBMULTISET

CONSTRAINTS

MODULE

SUBSTRING_REGEX

CONSTRUCTOR

MONTH

SYMMETRIC

CORR

MULTISET

SYSTEM

CORRESPONDING

NAMES

TEMPORARY

COVAR_POP

NATURAL

TERMINATE

COVAR_SAMP

NCHAR

THAN

CUBE

NCLOB

TIME

CUME_DIST

NEW

TIMESTAMP

CURRENT_CATALOG

NEXT

TIMEZONE_HOUR

CURRENT_DEFAULT_TRANSFORM_GROUP

NO

TIMEZONE_MINUTE

CURRENT_PATH

NONE

TRAILING

CURRENT_ROLE

NORMALIZE

TRANSLATE_REGEX

CURRENT_SCHEMA

NUMERIC

TRANSLATION

CURRENT_TRANSFORM_GROUP_FOR_TYPE

OBJECT

TREAT

CYCLE

OCCURRENCES_REGEX

TRUE

DATA

OLD

UESCAPE

DATE

ONLY

UNDER

DAY

OPERATION

UNKNOWN

DEC

ORDINALITY

UNNEST

DECIMAL

OUT

USAGE

DEFERRABLE

OVERLAY

USING

DEFERRED

OUTPUT

VALUE

DEPTH

PAD

VAR_POP

DEREF

PARAMETER

VAR_SAMP

DESCRIBE

PARAMETERS

VARCHAR

DESCRIPTOR

PARTIAL

VARIABLE

DESTROY

PARTITION

WHENEVER

DESTRUCTOR

PATH

WIDTH_BUCKET

DETERMINISTIC

POSTFIX

WITHOUT

DICTIONARY

PREFIX

WINDOW

DIAGNOSTICS

PREORDER

WITHIN

DISCONNECT

PREPARE

WORK

DOMAIN

PERCENT_RANK

WRITE

DYNAMIC

PERCENTILE_CONT

XMLAGG

EACH

PERCENTILE_DISC

XMLATTRIBUTES

ELEMENT

POSITION_REGEX

XMLBINARY

END-EXEC

PRESERVE

XMLCAST

EQUALS

PRIOR

XMLCOMMENT

EVERY

PRIVILEGES

XMLCONCAT

EXCEPTION

RANGE

XMLDOCUMENT

FALSE

READS

XMLELEMENT

FILTER

REAL

XMLEXISTS

FIRST

RECURSIVE

XMLFOREST

FLOAT

REF

XMLITERATE

FOUND

REFERENCING

XMLNAMESPACES

FREE

REGR_AVGX

XMLPARSE

FULLTEXTTABLE

REGR_AVGY

XMLPI

FUSION

REGR_COUNT

XMLQUERY

GENERAL

REGR_INTERCEPT

XMLSERIALIZE

GET

REGR_R2

XMLTABLE

GLOBAL

REGR_SLOPE

XMLTEXT

GO

REGR_SXX

XMLVALIDATE

GROUPING

REGR_SXY

YEAR

HOLD

REGR_SYY

ZONE

感谢阅读，希望能帮助到大家，谢谢大家对本站的支持！

SQL Function 自定义函数详解 目录产生背景（已经有了存储过程，为什么还要使用自定义函数）发展历史构成使用方法适用范围注意事项疑问内容产生背景（已经有了存储过程，为

Sqlserver 自定义函数 Function使用介绍 一.FUNCTION:在sqlserver中有3中自定义函数：标量函数/内联表值函数/多语句表值函数，首先总结下他们语法的异同点：同点：1.创建定义是一样的：a,CREAT

SQl Function 创建函数实例介绍 在SQL中系统已为我们提供了很非常丰富的函数：例：聚会函数avg,sum,count,max,min日期函数：Day,Month,Year等等为我们日常开发节省很多时间但是有一些特殊需