mysql **ÀàÐ͵ÄÏê½â

ʱ¼ä£ºä¯ÀÀ29´Î ·¢²¼ÈË£ºw304015115

mysql **ÀàÐ͵ÄÏê½â

Òѽâ¾öÎÊÌâ

¹È¸èw304015115Óû§ÔÚä¯ÀÀ29´ÎÌá½»Á˹ØÓÚ¡°ÎäÒÄɽmysql **ÀàÐ͵ÄÏê½â¡±µÄÌáÎÊ£¬»¶Ó­´ó¼ÒÓ¿Ô¾·¢±í×Ô¼ºµÄ¹Ûµã¡£Ä¿Ç°¹²ÓÐ1¸ö»Ø´ð£¬×îºó¸üÐÂÓÚ2024-08-14T15:58:54¡£Ï£Íû´ó¼ÒÄܹ»°ïÖúËý¡£

ÏêϸÎÊÌâÃèÊö¼°ÒÉÎÊ£ºÆÚ´ýÄúµÄ´ð°¸£¬Ç§ÑÔÍòÓï,±í´ï²»ÁËÎҵĸм¤Ö®Çé,ÎÒÒÑÃú¼ÇÔÚÐÄ £¡

Ï£ÍûÒÔϵĻشð£¬Äܹ»°ïÖúÄã¡£

µÚ1¸ö»Ø´ð

Óû§Ãû£ºAARONAILSA  

MySQL**¿âµÄ±íÊÇÒ»ÌøÁô·þתа¸¸ö¶þά±í£¬ÓÉÒ»¸ö»ò¶à¸ö**Áй¹³ÉÀ´×Ô¡£
ÿ¸ö**Áж¼ÓÐËüµÄÌØ¶¨ÀàÐÍ£¬¸ÃÀàÐ;ö¶¨ÁËMySQLÈçºÎ¿´´ý¸ÃÁÐ**£¬ÎÒÃÇ¿ÉÒÔ°ÑÕûÐÍÊýÖµ´æ·Åµ½×Ö·ûÀàÐ͵ÄÁÐÖУ¬MySQL331215ÎÊ´ðÔò»á°ÑËü¿´³É×Ö·û´®À´´¦Àí¡£
MySQLÖеÄÁÐÀàÐÍÓÐÈýÖÖ£ºÊýÖµÀà¡¢×Ö·û´®ÀàºÍÈÕÆÚ/ʱ¼äÀà¡£
´Ó´óÀàÀ´¿´ÁÐÀàÐͺÍÊýÖµÀà³äÐÍÒ»Ñù£¬¶¼ÊÇÖ»ÓÐÈýÖÖ¡£µ«Ã¿ÖÖÁÐÀàÐͶ¼»¹¿Éϸ·Ö¡£
ÏÂÃæ¶Ô¸÷ÖÖÁÐÀàÐͽøÐÐÏêϸ½éÉÜ¡£

ÊýÖµÀàµÄ**ÁÐÀàÐÍ
ÊýÖµÐ͵ÄÁÐÀàÐͰüÀ¨ÕûÐͺ͸¡µãÐÍÁ½´óÀàÔ²ÔìÇ×ÁËÁ÷¶ÈÃÞ°¡¡£

TINYINT£º1×ֽڷdz£Ð¡µÄÕýÕûÊý£¬´ø·ûºÅ£º-128~127£¬²»´ø·ûºÅ£º0~255
SMALLIN±±ÅÜT£º2×Ö½ÚСÕûÊý£¬´ø·ûºÅ£º-32768~32767£¬²»´ø·ûºÅ£º0~65535
MEDIUMINT£º3×Ö½ÚÖеȴóСµÄÕûÊý£¬´ø·ûºÅ£º-8388608~8388607£¬²»´ø·ûºÅ£º0~16777215
INT£º4×Ö½ÚɳÖÞÓѽÐÕë¼°±ê×¼ÕûÊý£¬´ø·ûºÅ£º-2147483648~2147483647£¬²»´ø·ûºÅ£º0~4294967295
BIGINT£º8×Ö½Ú´óÕûÊý£¬´ø·ûºÅ£º-92233720Ãⳬº¦½á36854775808~9233372036854775807Åúʼ£¬²»´ø·ûºÅ£º0~1844ͶÇïÁíÉóÈýСֻ6744073709551615
FLOAT£º4×Ö½Úµ¥¾«¶È¸¡µãÊý£¬×îС·ÇÁãÖµ£º+-1.175494351E-38£¬×î´ó·ÇÁãÖµ£º+-3.402823466E+38
DOUBLE£º8×Ö½ÚË«¾«¶È¸¡µãÊý£¬×îС·ÇÁãÖµ£º¸®³ö»°Òª+-2.2250738585072014E-308£¬×î´ó·ÇÁãÖµ£º+-1.7ÈÎÅÅÂäµ×ÂÉÁ£¸±ÃÀǧҲÎï976931348623157E+308
DECIMAL£ºM+2×Ö½ÚÒÔ×Ö·û´®ÐÎʽ±íʾµÄ¸¡µãÊý£¬ËüÁ½¸æÀÏÒæµÄȡֵ·¶Î§¿É±ä£¬ÓÉרÆðÅܾɿ­ÃËÕý¸ºÑÏÖ§¹ÜMºÍDµÄÖµ¾ö¶¨¡£

MYSQLÖ§³Ö´óÁ¿µÄÁÐÀàÐÍ£¬ËüÃÇ¿ÉÒÔ±»·ÖΪ3ÀࣺÊý×ÖÀàÐÍ¡¢ÈÕÆÚºÍʱ¼äÀàÐÍÒÔ¼°×Ö·û´®(×ÖУÇҷѽð·âÑ¡¹»Á³×ö¶·û)ÀàÐÍ¡£Õâ¸öÕ½ÚÊ×Ïȸø³ö¿ÉÓÃÀàÐ͵ĸÅÊö£¬²¢ÇÒ×ܽá¸÷ÀàÐÍËùÐèµÄ´æ´¢ÐèÇó£¬È»ºóÌṩ¸÷ÀàÐÍÖеÄÀàÐÍ·¶³ë¸üÏêϸµÄÃèÊö¡£¸ÅÊöÓÐÒâµØ¼ò»¯ÁË¡£¸üÏêϸµÄ˵Ã÷Ó¦¸Ã²Î¿¼ÌØÐ´ÁÐÀàÐ͵ĸ½¼ÓÐÅÏ¢£¬ÀýÈçÄãÄÜΪÆäÖ¸¶¨¶ÀÖµµÄÔÊÐí¸ñʽ¡£

MySQLÖ§³ÖµÄÁÐÀàÐÍÔÚÏÂÃæÁгö¡£ÏÂÁдúÂë×ÖĸÓÃÓÚÃè¸ÏÆ·ÒÕÎüСÓÖÂä´´×ïÊöÖУº

MÖ¸³ö×î´óµÄÏÔʾ³ß´ç¡£×î´óµÄÏÔʾ³ß´ç³¤¶ÈΪ255¡£DÊÊÓÃÓÚ¸¡µãÀàÐÍ¡£Ö¸ºõ·ÅÈÈËÙË«°®¶·ÏûЩ»®³ö¸úËæÔÚÊ®½øÖÆÐ¡ÊýµãºóµÄÊý×ÖÊýÁ¿¡£×î´ó¿ÉÄÜֵΪ30£¬µ«²»Ó¦´óÓÚM-2¡£
·½À¨ºÅ(¡°[¡±and¡°]¡±)Ö¸¶¨¿ÉÑ¡µÄÀàÐÍÐÞÊβ¿·Ý¡£

×¢Ò⣬Èç¹ûΪһ¸öÁÐÖ¸¶¨ÁËZEROFILL£¬MySQL½«×Ô¶¯ÎªÕâ¸öÁÐÌí¼ÓUNSIGNEDÊôÐÔ¡£

¾¯¸æ£ºÄãÓ¦¸ÃÖªµÀµ±ÔÚÁ½¸öÕûÊýÀàÐÍÖµÖÐʹÓüõ·¨Ê±£¬ÈçÓÐÒ»¸öΪUNSIGNEDÀàÐÍ£¬ÄÇô½á¹ûÒ²ÊÇÎÞ·ûºÅµÄ¡£²é¿´Õ½Ú6.3.5Castº¯Êý¡£

TINYINT[(M)][UNSIGNED][ZEROFILL]-128µ½127¡£ÎÞ·ûºÅµÄ·¶Î§ÊÇ0µ½255¡£
BITBOOLËüÃÇÊÇTINYINT(1)µÄͬÒå´Ê¡£
SMALLINT[(M)][UNSIGNED][ZEROFILL]Ò»¸öСÕûÊý¡£ÓзûºÅµÄ·¶Î§ÊÇ-32768µ½32767¡£ÎÞ·ûºÅµÄ·¶Î§ÊÇ0µ½65535¡£
MEDIUMINT[(M)][UNSIGNED][ZEROFILL]Ò»¸öÖеȴóСµÄÕûÊý¡£ÓзûºÅµÄ·¶Î§ÊÇ-8388608µ½8388607¡£ÎÞ·ûºÅµÄ·¶Î§ÊÇ0µ½16777215¡£
INT[(M)][UNSIGNED][ZEROFILL]Ò»¸öÕý³£´óСµÄÕûÊý¡£ÓзûºÅµÄ·¶Î§ÊÇ-2147483648µ½2147483647¡£ÎÞ·ûºÅµÄ·¶Î§ÊÇ0µ½4294967295¡£
INTEGER[(M)][UNSIGNED][ZEROFILL]INTµÄͬÒå´Ê¡£
BIGINT[(M)][UNSIGNED][ZEROFILL]Ò»¸ö´óµÄÕûÊý¡£ÓзûºÅµÄ·¶Î§ÊÇ-9223372036854775808µ½9223372036854775807¡£ÎÞ·ûºÅµÄ·¶Î§ÊÇ0µ½18446744073709551615¡£
ÄãÓ¦¸ÃÖªµÀµÄÓйØBIGINTÁеÄһЩÊÂÇ飺
BIGINT»òDOUBLEÖµÀ´Íê³ÉµÄ£¬Òò´ËÄã²»Ó¦¸ÃʹÓôóÓÚ9223372036854775807(63bits)µÄÎÞ·ûºÅ´óÕûÊý£¬³ýÁËλº¯ÊýÖ®Í⣡Èç¹ûÄãÕâÑù×öÁË£¬½á¹ûÖеÄijЩ´óÊý×Ö¿ÉÄÜ»á³ö´í£¬ÒòΪ½«BIGINTת»»³ÉDOUBLEʱ**ÉúÁËÉáÈë´íÎó¡£MySQL4.0ÔÚÏÂÁÐÇé¿öÏ¿ÉÒÔ´¦ÀíBIGINT£º
ÔÚÒ»¸öBIGINTÁÐÖÐʹÓÃÕûÊý´æ´¢Ò»¸ö´óµÄÎÞ·ûºÅÖµ¡£
ÔÚMIN(big_int_column)ºÍMAX(big_int_column)ÖС£
µ±Á½¸ö²Ù×÷Êý¶¼ÊÇÕûÊýʱʹÓòÙ×÷·û(+¡¢-¡¢*¡¢µÈ)¡£
ͨ³£Äã¿ÉÒÔÔÚÒ»¸öBIGINTÁÐÖÐÒÔ×Ö·û´®·½Ê½´æ´¢µÄÒ»¸ö¾«È·µÄÕûÊý¡£ÔÚÕâÖÖÇé¿öÏ£¬MySQL½«Ö´ÐÐÒ»¸ö×Ö·û´®µ½Êý×ÖµÄת»»£¬°üÀ¨ÎÞintermediateµÄË«¾«¶È±íʾ·¨¡£
µ±Á½¸ö²ÎÊý¾ùÊÇÕûÊýֵʱ£¬¡°-¡±¡¢¡°+¡±ºÍ¡°*¡±½«Ê¹ÓÃBIGINTÔËË㣡Õâ¾ÍÒâζ×Å£¬Èç¹ûÁ½¸ö´óÕûÊýµÄ³Ë»ý(»òº¯ÊýµÄ½á¹û·µ»ØÕûÊý)µÄ½á¹û´óÓÚ9223372036854775807ʱ£¬Äã¿ÉÄÜ»áµÃµ½ÒâÏë²»µ½µÄ½á¹û¡£
FLOAT(precision)[UNSIGNED][ZEROFILL]Ò»¸ö¸¡µãÐÍÊý×Ö¡£
precision¿ÉÒÔÊÇ<=24×÷Ϊһ¸öµ¥¾«¶ÈµÄ¸¡µãÊý×ֺͽéÓÚ25ºÍ53Ö®¼ä×÷Ϊһ¸öË«¾«¶ÈµÄ¸¡µãÊý×Ö¡£ÕâЩÀàÐÍÓëÏÂÃæÃèÊöµÄFLOATºÍDOUBLEÀàÐÍÏàËÆ¡£FLOAT(X)ÓÐÓëÏàÓ¦µÄFLOATºÍDOUBLEÀàÐÍͬÑùµÄ·¶Î§£¬µ«ÊÇÏÔʾ³ß´çºÍÊ®½øÖÆÐ¡ÊýλÊýÊÇ䶨ÒåµÄ¡£ÔÚMySQL3.23ÖУ¬ËüÊÇÒ»¸öÕæÊµµÄ¸¡µãÖµ¡£¶øÔÚMySQLÔçÆÚµÄ°æ±¾ÖУ¬FLOAT(precision)ͨ³£ÓÐ2СÊýλ¡£×¢Ò⣬ÓÉÓÚÔÚMySQLÖÐËùÓеļÆËã¶¼ÊÇÒÔË«¾«¶ÈÖ´Ðеģ¬ËùÒÔʹÓÃFLOAT¿ÉÄÜ´øÀ´Ò»Ð©ÒâÏë²»µ½µÄÎÊÌâ¡£²é¿´Õ½ÚA.5.6½â¾öûÓÐÆ¥ÅäÐеÄÎÊÌâ¡£

FLOAT[(M,D)][UNSIGNED][ZEROFILL]Ò»¸öСµÄ(µ¥¾«¶È)¸¡µãÊý×Ö¡£ÔÊÐíµÄÖµÊÇ-3.402823466E+38µ½-1.175494351E-38¡¢0ºÍ1.175494351E-38µ½3.402823466E+38¡£Èç¹ûUNSIGNED±»Ö¸¶¨£¬¸ºÖµÊDz»ÔÊÐíµÄ¡£MÊÇÏÔʾ¿í¶È£¬DÊÇСÊýλÊý¡£FLOATûÓвÎÊý»òÓÐX<=24µÄFLOAT(X)´ú±íÒ»¸öµ¥¾«¶ÈµÄ¸¡µãÊý×Ö¡£

DOUBLE[(M,D)][UNSIGNED][ZEROFILL]Ò»¸öÕý³£´óСµÄ(Ë«¾«¶È)¸¡ÉÏÊý×Ö¡£ÔÊÐíµÄÖµÊÇ-1.7976931348623157E+308µ½-2.2250738585072014E-308¡¢0ºÍ2.2250738585072014E-308µ½1.7976931348623157E+308¡£Èç¹ûUNSIGNED±»Ö¸¶¨£¬¸ºÖµÊDz»ÔÊÐíµÄ¡£MÊÇÏÔʾ¿í¶È£¬DÊÇСÊýλÊý¡£DOUBLEûºú²ÎÊý»òÓÐ25<=X<=53µÄFLOAT(X)´ú±íÒ»¸öË«¾«¶ÈµÄ¸¡µãÊý×Ö¡£

DOUBLEPRECISION[(M,D)][UNSIGNED][ZEROFILL]
REAL[(M,D)][UNSIGNED][ZEROFILL]ËüÃÇÊÇDOUBLEͬÒå´Ê¡£
DECIMAL[(M[,D])][UNSIGNED][ZEROFILL]Ò»¸öδѹËõ(unpacked)µÄ¸¡µãÊý¡£ÔË×÷Èçͬһ¸öCh**ARÁУº¡°unpacked¡±Òâζ×ÅÊý×ÖÊÇÒÔÒ»¸ö×Ö·û´®´æ´¢µÄ£¬ÖµµÄÿһλ½«Ê¹ÓÃÒ»¸ö×Ö·û¡£Ð¡Êýµã²¢ÇÒ¶ÔÓÚ¸ºÊý£¬¡°-¡±·ûºÅ²»ÔÚMÖмÆËã(µ«ÊÇËüÃǵĿռäÊDZ»±£ÁôµÄ)¡£Èç¹ûDÊÇ0£¬Öµ½«Ã»ÓÐСÊýµã»òСÊý²¿·Ý¡£DECIMALÖµµÄ×î´ó·¶Î§ÓëDOUBLEÒ»Ö£¬µ«ÊǶÔÓÚÒ»¸ö¸ø¶¨µÄDECIMALÁУ¬Êµ¼ÊµÄ·¶Î§¿ÉÒÔ±»ËùÑ¡ÔñµÄMºÍDÏÞÖÆ¡£Èç¹ûUNSIGNED±»Ö¸¶¨£¬¸ºÖµÊDz»ÔÊÐíµÄ¡£Èç¹ûD±»ºöÂÔ£¬È±Ê¡Îª0¡£Èç¹ûM±»ºöÂÔ£¬È±Ê¡Îª10¡£ÔÚMySQL3.23ÒÔǰ£¬M²ÎÊý±ØÐë°üº¬·ûºÅÓëСÊýµãËùÐèµÄ¿Õ¼ä¡£
DEC[(M[,D])][UNSIGNED][ZEROFILL]
**MERIC[(M[,D])][UNSIGNED][ZEROFILL]DECIMALµÄͬÒå´Ê¡£

DATEÒ»¸öÈÕÆÚ¡£Ö§³ÖµÄ·¶Î§ÊÇ'1000-01-01'µ½'9999-12-31'¡£MySQLÒÔ'YYYY-MM-DD'¸ñʽÏÔʾDATEÖµ£¬µ«ÊÇÔÊÐíÄãÒÔ×Ö·û´®»òÊý×Ö¸øÒ»¸öDATEÁи³Öµ¡£²é¿´Õ½Ú6.2.2.2DATETIME¡¢DATEºÍTIMESTAMPÀàÐÍ¡£

DATETIMEÒ»¸öÈÕÆÚºÍʱ¼äµÄ×éºÏ¡£Ö§³ÖµÄ·¶Î§ÊÇ'1000-01-0100:00:00'µ½'9999-12-3123:59:59'¡£MySQLÒÔ'YYYY-MM-DDh**h**:MM:SS'¸ñʽÏÔʾDATETIMEÖµ£¬µ«ÊÇÔÊÐíÄãÒÔ×Ö·û´®»òÊý×Ö¸øÒ»¸öDATETIMEÁи³Öµ¡£²é¿´Õ½Ú6.2.2.2DATETIME¡¢DATEºÍTIMESTAMPÀàÐÍ¡£

TIMESTAMP[(M)]Ò»¸öʱ¼ä´Á¡£·¶Î§ÊÇ'1970-01-0100:00:00'µ½2037Äê¼äµÄÈÎÒâʱ¿Ì¡£MySQL4.0ºÍ¸üÔç°æ±¾ÖУ¬TIMESTAMPÖµÊÇÒÔYYYYMMDDh**h**MMSS¡¢YYMMDDh**h**MMSS¡¢YYYYMMDD»òYYMMDD¸ñʽÏÔʾµÄ£¬ËüÈ¡¾öÓÚMÊÇ·ñÊÇ14(»òÊ¡ÂÔ)¡¢12¡¢8»ò6£¬µ«ÊÇÔÊÐíÄãÒÔ×Ö·û´®»òÊý×Ö¸øÒ»¸öTIMESTAMPÁи³Öµ¡£´ÓMySQL4.1¿ªÊ¼£¬TIMESTAMPÒÔ'YYYY-MM-DDh**h**:MM:DD'¸ñʽ×÷Ϊ×Ö·û·µ»Ø¡£Èç¹ûÄãÄãÏ£ÍûÒÔÊý×ÖÐÎʽ·µ»ØÔò±ØÐëÔÚ¸Ãʱ¼ä´Á×ֶκó¼ÓÉÏ+0¡£²»Í¬µÄʱ¼ä´Á³¤¶ÈÊDz»Ö§³ÖµÄ¡£´ÓMySQL4.0.12¿ªÊ¼£¬Ñ¡Ïî--new¿ÉÒÔ±»ÓÃÀ´ÊþÎñÆ÷Óë4.1Ò»ÑùÔË×÷¡£TIMESTAMPÁÐÓÐÒæÓڼǼһ¸öIN**RT»òUPDATE²Ù×÷µÄÈÕÆÚºÍʱ¼ä£¬ÒòΪÈç¹ûÄã×Ô¼ºÃ»ÓиøËü¸³Öµ£¬Ëü½«±»×Ô¶¯µØÉèÖÃΪ×î½üÒ»´Î²Ù×÷µÄÈÕÆÚºÍʱ¼ä¡£Ò²¿ÉÒÔͨ¹ý¸øËü¸³Ò»¸ö**LL¶øÊ¹ËüÉèÖÃΪµ±Ç°µÄÈÕÆÚºÍʱ¼ä¡£²é¿´Õ½Ú6.2.2DateºÍTimeÀàÐÍ¡£²ÎÊýMÖ»Ó°ÏìÒ»¸öTIMESTAMPÁеÄÏÔʾ¸ñʽ£»ËüµÄÖµ×ÜÊÇÕ¼ÓÃ4¸ö×Ö½Ú´æ´¢¡£×¢Ò⣬µ±TIMESTAMP(M)ÁеÄMÊÇ8»ò14ʱ£¬Ëü·µ»ØµÄÊÇÊý×Ö¶øÆäËüµÄTIMESTAMP(M)Áзµ»ØµÄÊÇ×Ö·û´®¡£Õâ½ö½öÊÇΪÁË¿ÉÒÔ¿É¿¿µØ×ª´¢²¢»Ö¸´µ½ÆäËü¸ñʽµÄ±íÖС£²é¿´Õ½Ú6.2.2.2DATETIME¡¢DATEºÍTIMESTAMPÀàÐÍ¡£TIMEÒ»¸öʱ¼ä¡£·¶Î§ÊÇ'-838:59:59'µ½'838:59:59'¡£MySQLÒÔ'h**h**:MM:SS'¸ñʽÏÔʾTIMEÖµ£¬µ«ÊÇÔÊÐíÄãʹÓÃ×Ö·û´®»òÊý×ÖÀ´¸øTIMEÁи³Öµ¡£²é¿´Õ½Ú6.2.2.3TIMEÀàÐÍ¡£YEAR[(2|4)]Ò»¸ö2»ò4λÊý×Ö¸ñʽµÄÄê(ȱʡΪ4λ)¡£ÔÊÐíµÄÖµÊÇ1901µ½2155¡¢0000(4λÄê¸ñʽ)ÒÔ¼°Ê¹ÓÃ2λ¸ñʽµÄ1970-2069(70-69)¡£MySQLÒÔYYYY¸ñʽÏÔʾYEARÖµ£¬µ«ÊÇÔÊÐíÄãʹÓÃ×Ö·û´®»òÊý×ÖÀ´¸øYEARÁи³Öµ¡£(YEARÀàÐÍÔÚMySQL3.22֮ǰ²»Ö§³Ö¡£)²é¿´Õ½Ú6.2.2.4YEARÀàÐÍ¡£

[NATIONAL]Ch**AR(M)[BINARY]Ò»¸ö¶¨³¤µÄ×Ö·û´®£¬µ±´æ´¢Ê±£¬×ÜÊÇÒÔ¿Õ¸ñÌîÂúÓұߵ½Ö¸¶¨µÄ³¤¶È¡£MµÄ·¶Î§ÊÇ0µ½255(ÔÚMySQL3.23°æ±¾Ö®Ç°Îª1µ½255)¡£µ±¸ÃÖµ±»¼ìË÷ʱ£¬Î²²¿¿Õ¸ñ½«±»É¾³ý¡£Ch**ARÖµ¸ù¾ÝȱʡµÄ×Ö·û¼¯½øÐкöÂÔ´óСдµÄÅÅË÷Óë±È½Ï£¬³ý·ÇÖ¸¶¨Á˹ؼü´ÊBINARY¡£NATIONALCh**AR(»ò¶ÌÐÎʽNCh**AR)ÊÇÒÔANSISQL·½Ê½¶¨ÒåÒ»¸öCh**ARÁУ¬Ëü½«Ê¹ÓÃȱʡµÄ×Ö·û¼¯¡£ÕâÔÚMySQLÖÐÊÇĬÈϵġ£
Ch**ARÊÇCh**ARACTERµÄËõд¡£MySQLÔÊÐíÒÔCh**AR(0)ÀàÐͽ¨Á¢Ò»¸öÁС£Ò»Ð©ÀϳÌÐòÔËÐÐʱ±ØÐèÒ»¸öÁУ¬È´ÓÖ²¢²»Ê¹ÓÃÕâ¸öÁеÄÖµ£¬Äã¾Í²»µÃ²»ÎªÁËÊÊÓ¦Ëü¶ø½¨Á¢¸ÃÁУ¬ÔÚÕâÇé¿öÏ£¬Ch**AR(0)½«ÊǺÜÓÐÒæµÄ¡£µ±ÐèÒªÒ»¸öÁнö±£´æÁ½¸öֵʱ£ºÒ»¸öΪCh**AR(0)(¸ÃÁÐûÓж¨ÒåΪNOT**LL)£¬Õ⽫½öÕ¼ÓÃÒ»¸ö±ÈÌØÎ»À´´æ´¢2¸öÖµ£º**LL»ò""¡£²é¿´Õ½Ú6.2.3.1Ch**ARºÍVARCh**ARÀàÐÍ¡£Ch**ARÕâÊÇCh**AR(1)µÄͬÒå´Ê¡£

[NATIONAL]VARCh**AR(M)[BINARY]Ò»¸ö±ä³¤µÄ×Ö·û´®¡£×¢Ò⣺β²¿µÄ¿Õ¸ñÔڴ洢ʱ½«»á±»É¾³ý(ÕâÓëANSISQLÔ¼¹æ²»Í¬)¡£MµÄ·¶Î§ÊÇ0µ½255(ÔÚMySQL4.0.2֮ǰµÄ°æ±¾ÖÐÊÇ1µ½255)¡£
VARCh**ARÖµÒÔ´óСдºöÂÔ·½Ê½½øÐÐÅÅË÷Óë±È½Ï£¬³ý·Ø¼ü´ÊBINARY±»Ö¸¶¨¡£²é¿´Õ½Ú6.5.3.1ÒþʽµÄÁж¨Òå±ä»¯¡£VARCh**ARÊÇCh**ARACTERVARYINGµÄËõд¡£²é¿´Õ½Ú6.2.3.1Ch**ARºÍVARCh**ARÀàÐÍ¡£
TINYBLO**INYTEXTÒ»¸öBLOB»òTEXTÁУ¬×î´ó³¤¶ÈΪ255(2^8-1)¸ö×Ö·û¡£²é¿´Õ½Ú6.5.3.1ÒþʽµÄÁж¨Òå±ä»¯¡£²é¿´Õ½Ú6.2.3.2BLOBºÍTEXTÀàÐÍ¡£
BLO**EXTÒ»¸öBLOB»òTEXTÁУ¬×î´ó³¤¶ÈΪ65535(2^16-1)¸ö×Ö·û¡£²é¿´Õ½Ú6.5.3.1ÒþʽµÄÁж¨Òå±ä»¯¡£²é¿´Õ½Ú6.2.3.2BLOBºÍTEXTÀàÐÍ¡£
MEDIUMBLOBMEDIUMTEXTÒ»¸öBLOB»òTEXTÁУ¬×î´ó³¤¶ÈΪ16777215(2^24-1)¸ö×Ö·û¡£²é¿´Õ½Ú6.5.3.1ÒþʽµÄÁж¨Òå±ä»¯¡£²é¿´Õ½Ú6.2.3.2BLOBºÍTEXTÀàÐÍ¡£
LONGBLOBLONGTEXTÒ»¸öBLOB»òTEXTÁУ¬×î´ó³¤¶ÈΪ4294967295(2^32-1)¸ö×Ö·û¡£²é¿´Õ½Ú6.5.3.1ÒþʽµÄÁж¨Òå±ä»¯¡£×¢Ò⣬ÓÉÓÚ·þÎñÆ÷/¿Í»§¶ËµÄЭÒéÒÔ¼°MyISAM±íͨ³£ÓÐÒ»¸ö16MÿͨÐŰü/±íÐеÄÏÞÖÆ£¬ÄãÈÔÈ»²»ÄÜʹÓÃÕâ¸öÀàÐ͵ÄÕû¸ö·¶Î§¡£²é¿´Õ½Ú6.2.3.2BLOBºÍTEXTÀàÐÍ¡£E**M('value1','value2',)Ò»¸öÃÙÀàÐÍ¡£Ò»¸ö½öÄÜÓÐÒ»¸öÖµµÄ×Ö·û´®¶ÔÏó£¬Õâ¸öֵѡ×ÔÖµÁÐ'value1'¡¢'value2'¡¢¡¢**LL»òÌØÊâµÄ""³ö´íÖµ¡£Ò»¸öE**MÁпÉÒÔÓÐ×î´ó65535²»Í¬µÄÖµ¡£²é¿´Õ½Ú6.2.3.3E**MÀàÐÍ¡£**T('value1','value2',)Ò»¸ö¼¯ºÏ¡£Ò»¸öÄÜÓÐÁã¸ö»ò¸ü¶à¸öÖµµÄ×Ö·û´®¶ÔÏ󣬯äÖÐÿ¸öÖµ±ØÐëÑ¡×ÔÖµÁÐ'value1'¡¢'value2'¡¢¡£Ò»¸ö**TÁпÉÒÔÓÐ×î´ó64¸ö³ÉÔ±¡£²é¿´Õ½Ú6.2.3.4**TÀàÐÍ¡£
MySQLÖ§³ÖËùÓеÄANSI/ISOSQL92Êý×ÖÀàÐÍ¡£ÕâЩÀàÐͰüÀ¨×¼È·Êý×ÖµÄ**ÀàÐÍ(**MERIC¡¢DECIMAL¡¢INTEGERºÍSMALLINT)£¬Ò²°üÀ¨½üËÆÊý×ÖµÄ**ÀàÐÍ(FLOAT¡¢REALºÍDOUBLEPRECISION)¡£¹Ø¼ü´ÊINTÊÇINTEGERµÄͬÒå´Ê£¬¹Ø¼ü´ÊDECÊÇDECIMALµÄͬÒå´Ê¡£

**MERICºÍDECIMALÀàÐͱ»MySQLÒÔͬÑùµÄÀàÐÍʵÏÖ£¬ÕâÔÚSQL92±ê×¼ÖÐÊÇÔÊÐíµÄ¡£ËûÃÇÓÃÓÚ±£´æ¶Ô׼ȷ¾«¶ÈÓÐÖØÒªÒªÇóµÄÖµ£¬ÀýÈçÓë½ðÇ®ÓйصÄ**¡£µÔËüÃÇÖеÄÖ®Ò»ÉùÃ÷Ò»¸öÁÐʱ£¬¾«¶ÈºÍÊýÖµ·¶Î§¿ÉÒÔ(ͨ³£ÊÇ)±»Ö¸¶¨£»ÀýÈ磺

salaryDECIMAL(5,2)
ÔÚÕâ¸öÀý×ÓÖУ¬5(¾«¶È(precision))´ú±íÖØÒªµÄÊ®½øÖÆÊý×ÖµÄÊýÄ¿£¬2(**·¶Î§(scale))´ú±íÔÚСÊýµãºóµÄÊý×ÖλÊý¡£ÔÚÕâÖÖÇé¿öÏ£¬Òò´Ë£¬salaryÁпÉÒÔ´æ´¢µÄÖµ·¶Î§ÊÇ´Ó-99.99µ½99.99¡£(ʵ¼ÊÉÏMySQLÔÚÕâ¸öÁÐÖпÉÒÔ´æ´¢µÄÊýÖµ¿ÉÒÔÒ»Ö±µ½999.99£¬ÒòΪËüûÓд洢ÕýÊýµÄ·ûºÅ)¡£

ÒëÕß×¢£º

MÓëD¶ÔDECIMAL(M,D)ȡֵ·¶Î§µÄÓ°Ïì

ÀàÐÍ˵Ã÷ȡֵ·¶Î§£¨MySQL<3.23£©È¡Öµ·¶Î§£¨MySQL>=3.23£©
DECIMAL(4,1)-9.9µ½99.9-999.9µ½9999.9
DECIMAL(5,1)-99.9µ½999.9-9999.9µ½99999.9
DECIMAL(6,1)-999.9µ½9999.9-99999.9µ½999999.9
DECIMAL(6,2)-99.99µ½999.99-9999.99µ½99999.99
DECIMAL(6,3)-9.999µ½99.999-999.999µ½9999.999

#ÔÚMySQL3.23¼°ÒÔºóµÄ°æ±¾ÖУ¬DECIMAL(M,D)µÄȡֵ·¶Î§µÈÓÚÔçÆÚ°æ±¾ÖеÄDECIMAL(M+2,D)µÄȡֵ·¶Î§¡£×¢ÊͽáÊø£º
ÔÚANSI/ISOSQL92ÖУ¬¾ä·¨DECIMAL(p)µÈ¼ÛÓÚDECIMAL(p,0)¡£Í¬ÑùµÄ£¬ÔÚÖ´Ðб»ÔÊÐí¾ö¶¨ÖµpµÄµØ·½,¾ä·¨DECIMALµÈ¼ÛÓÚDECIMAL(p,0)¡£MySQLĿǰ»**»Ö§³ÖDECIMAL/**MERIC**ÀàÐ͵ÄÕâЩ±äÌåÐÎʽÖеÄÈÎÒ»ÖÖ¡£Ò»°ãÀ´ËµÕâ²¢²»ÊÇÒ»¸öÑÏÖØµÄÎÊÌ⣬ͨ¹ýÃ÷È·µØ¿ØÖƾ«¶ÈºÍÊýÖµ·¶Î§¿ÉÒԵõ½ÕâЩÀàÐ͵ÄÖ÷Òª¹¦ÄÜÒæ´¦¡£

DECIMALºÍ**MERICÖµÊÇ×÷Ϊ×Ö·û´®´æ´¢µÄ£¬¶ø²»ÊÇ×÷Ϊ¶þ½øÖƸ¡µãÊý£¬ÒԱ㱣»¤ÕâЩֵµÄÊ®½øÖƾ«È·¶È¡£Ò»¸ö×Ö·ûÓÃÓÚÊýÖµµÄÿһλ¡¢Ð¡Êýµã(Èç¹ûscale>0)ºÍ¡°-¡±·ûºÅ(¶ÔÓÚ¸ºÖµ)¡£Èç¹ûscaleÊÇ0£¬DECIMALºÍ**MERICÖµ²»°üº¬Ð¡Êýµã»òСÊý²¿·Ö¡£

DECIMALºÍ**MERICÖµµÄ×î´ó·¶Î§ÓëDOUBLEÒ»Ö£¬µ«ÊǶÔÓÚÒ»¸ö¸ø¶¨µÄDECIMAL»ò**MERICÁУ¬ËüµÄʵ¼Ê·¶Î§¿ÉÖÆ¶¨¸ÃÁÐʱµÄprecision»òscaleÏÞÖÆ¡£µ±ÕâÑùµÄÁб»¸³¸øÁËСÊýµãµÄλÊý³¬¹ýscaleËùÖ¸¶¨µÄֵʱ£¬¸Ã½«¸ù¾Ýscale½øÐÐËÄÉáÎåÈë¡£µ»¸öDECIMAL»ò**MERICÁб»¸³ÓëÒ»¸ö´óС³¬¹ýÖ¸¶¨(»òȱʡ)µÄprecisionandscaleµÄÏÞֶΧʱ£¬MySQLÒÔ¸ÃÁз¶Î§µÄ¶ËµãÖµ´æ´¢¸ÃÖµ¡£