时间:2020-11-03 13:29 作者:admin

前言

mysql/' target='_blank'>mysql和Oracle的关键字还是不尽相同的，在Oracle数据库中，我们的数据表中定义了大量的code字段用来表示主键，但是在MySQL中code是关键字，使用以前的处理方法就有些“水土不服”。

下面我们来了解一下MySQL中的关键字和保留字。

什么是关键字和保留字

关键字是指在SQL中有意义的字。 某些关键字（例如SELECT，DELETE或BIGINT）是保留的，需要特殊处理才能用作表和列名称等标识符。 这一点对于内置函数的名称也适用。

如何使用关键字和保留字

非保留关键字允许作为标识符，不需要加引号。 如果您要适用保留字作为标识符，就必须适用引号。

举个例子，BEGIN和END是关键字，但不是保留字，因此它们用作标识符不需要引号。 INTERVAL是保留关键字，必须加上引号才能用作标识符。

mysql>mysql> use hoegh;Database changedmysql>mysql> CREATE TABLE interval (begin INT, end INT);ERROR 1064 (42000):mysql>mysql> CREATE TABLE `interval` (begin INT, end INT);Query OK, 0 rows affected (0.42 sec)mysql>mysql> show create table `interval`;+----------+---------------------------------------------------------| Table | Create Table+----------+---------------------------------------------------------| interval | CREATE TABLE `interval` ( `begin` int(11) DEFAULT NULL, `end` int(11) DEFAULT NULL) ENGINE=InnoDB DEFAULT CHARSET=latin1 |+----------+---------------------------------------------------------1 row in set (0.00 sec)mysql>

我们看到，第一条语句中表名使用了保留字interval，执行失败；

第二条语句对interval加了引号，执行成功。

在这里需要注意的是，引号必须是反引号，而非单引号。否则会报错，如下所示：

mysql>mysql> drop table `interval`;--使用反引号Query OK, 0 rows affected (0.11 sec)mysql>mysql> create table 'interval' (begin INT, end INT);--使用单引号，报错ERROR 1064 (42000):mysql>

有一个例外

如果标识符在限定名称（数据库名）的句点之后，即使是保留关键字也不需要引号。

我们以hoegh数据库为例，如果表名写为hoegh.interval就不需要对保留字interval加引号了。

mysql>mysql> create table hoegh.interval (begin INT, end INT);Query OK, 0 rows affected (0.19 sec)mysql>mysql> show create table hoegh.interval;+----------+---------------------------------------------------------| Table | Create Table+----------+---------------------------------------------------------| interval | CREATE TABLE `interval` ( `begin` int(11) DEFAULT NULL, `end` int(11) DEFAULT NULL) ENGINE=InnoDB DEFAULT CHARSET=latin1 |+----------+---------------------------------------------------------1 row in set (0.00 sec)mysql>

关于使用内置函数名称

允许内置函数的名称可以作为标识符，但最好谨慎使用。例如，COUNT作为列名称是合法的。但是，默认情况下，在函数名和后面的（之间的函数调用中不允许有空格。这个限制使解析器能够区分名称是用于函数调用还是用在非函数上下文中。

附录

在某些时候，您可能需要升级到更高版本，因此最好查看一下未来的保留字。您可以在涵盖更高版本的MySQL的手册中找到这些。对于表中的大多数保留字，在标准SQL中禁止作为列或表的名称（例如，GROUP）。其中一些保留字，是由于MySQL需要它们并使用一个yacc解析器。

以下列出三张表格：

第一个表格10.2显示MySQL 5.7中的关键字和保留字。保留的关键字标记为（R）。此外，_FILENAME是保留的。

第二个表格10.3显示MySQL 5.7相比5.6版本新增的保留字。

第三个表格10.4显示MySQL 5.7相比5.6版本删除的保留字。

Table 10.2 Keywords and Reserved Words in MySQL 5.7

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) X509 XA XID[ag] XML XOR(R) YEAR YEAR_MONTH(R) ZEROFILL(R)

[a]ACCOUNT: added in 5.7.6 (nonreserved)

[b]ALWAYS: added in 5.7.6 (nonreserved)

[c]CHANNEL: added in 5.7.6 (nonreserved)

[d]COMPRESSION: added in 5.7.8 (nonreserved)

[e]ENCRYPTION: added in 5.7.11 (nonreserved)

[f]FILE_BLOCK_SIZE: added in 5.7.6 (nonreserved)

[g]FILTER: added in 5.7.3 (nonreserved)

[h]FOLLOWS: added in 5.7.2 (nonreserved)

[i]GENERATED: added in 5.7.6 (reserved)

[j]GROUP_REPLICATION: added in 5.7.6 (nonreserved)

[k]INSTANCE: added in 5.7.11 (nonreserved)

[l]JSON: added in 5.7.8 (nonreserved)

[m]MASTER_TLS_VERSION: added in 5.7.10 (nonreserved)

[n]MAX_STATEMENT_TIME: added in 5.7.4 (nonreserved); removed in 5.7.8

[o]NEVER: added in 5.7.4 (nonreserved)

[p]NONBLOCKING: removed in 5.7.6

[q]OLD_PASSWORD: removed in 5.7.5

[r]OPTIMIZER_COSTS: added in 5.7.5 (reserved)

[s]PARSE_GCOL_EXPR: added in 5.7.6 (reserved); became nonreserved in 5.7.8

[t]PRECEDES: added in 5.7.2 (nonreserved)

[u]REPLICATE_DO_DB: added in 5.7.3 (nonreserved)

[v]REPLICATE_DO_TABLE: added in 5.7.3 (nonreserved)

[w]REPLICATE_IGNORE_DB: added in 5.7.3 (nonreserved)

[x]REPLICATE_IGNORE_TABLE: added in 5.7.3 (nonreserved)

[y]REPLICATE_REWRITE_DB: added in 5.7.3 (nonreserved)

[z]REPLICATE_WILD_DO_TABLE: added in 5.7.3 (nonreserved)

[aa]REPLICATE_WILD_IGNORE_TABLE: added in 5.7.3 (nonreserved)

[ab]ROTATE: added in 5.7.11 (nonreserved)

[ac]STORED: added in 5.7.6 (reserved)

[ad]VALIDATION: added in 5.7.5 (nonreserved)

[ae]VIRTUAL: added in 5.7.6 (reserved)

[af]WITHOUT: added in 5.7.5 (nonreserved)

[ag]XID: added in 5.7.5 (nonreserved)

Table 10.3 Keywords and Reserved Words Added in MySQL 5.7 Compared to MySQL 5.6

ACCOUNT ALWAYS CHANNEL COMPRESSION ENCRYPTION FILE_BLOCK_SIZE FILTER FOLLOWS GENERATED(R) GROUP_REPLICATION INSTANCE JSON MASTER_TLS_VERSION NEVER OPTIMIZER_COSTS(R) PARSE_GCOL_EXPR PRECEDES REPLICATE_DO_DB REPLICATE_DO_TABLE REPLICATE_IGNORE_DB REPLICATE_IGNORE_TABLE REPLICATE_REWRITE_DB REPLICATE_WILD_DO_TABLE REPLICATE_WILD_IGNORE_TABLE ROTATE STACKED STORED(R) VALIDATION VIRTUAL(R) WITHOUT XID

Table 10.4 Keywords and Reserved Words Removed in MySQL 5.7 Compared to MySQL 5.6

OLD_PASSWORD

总结

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