mysqlµÄ×Ö·û´®º¯Êý
¶ÔÓÚÕë¶Ô×Ö·û´®Î»ÖõIJÙ×÷£¬µÚÒ»¸öλÖñ»±ê¼ÇΪ1¡£
ASCII(str) ·µ»Ø×Ö·û´®strµÄ×î×óÃæ×Ö·ûµÄASCII´úÂëÖµ¡£Èç¹ûstrÊÇ¿Õ×Ö·û´®£¬·µ»Ø0¡£Èç¹ûstrÊÇNULL£¬·µ»ØNULL¡£
mysql> select ASCII('2');
-> 50
mysql> select ASCII(2);
-> 50
mysql> select ASCII('dx');
-> 100
Ò²¿É²Î¼ûORD()º¯Êý¡£
ORD(str) Èç¹û×Ö·û´®str×î×óÃæ×Ö·ûÊÇÒ»¸ö¶à×Ö½Ú×Ö·û£¬Í¨¹ýÒÔ¸ñʽ((first byte ASCII code)*256+(second byte ASCII code))[*256+third byte ASCII code...]·µ»Ø×Ö·ûµÄASCII´úÂëÖµÀ´·µ»Ø¶à×Ö½Ú×Ö·û´úÂë¡£Èç¹û×î×óÃæµÄ×Ö·û²»ÊÇÒ»¸ö¶à×Ö½Ú×Ö·û¡£·µ»ØÓëASCII()º¯Êý·µ»ØµÄÏàֵͬ¡£
mysql> select ORD('2');
-> 50
CONV(N,from_base,to_base) ÔÚ²»Í¬µÄÊý×Ö»ùÖ®¼ä±ä»»Êý×Ö¡£·µ»ØÊý×ÖNµÄ×Ö·û´®Êý×Ö£¬´Ófrom_base»ù±ä»»Îªto_base»ù£¬Èç¹ûÈκβÎÊýÊÇNULL£¬·µ»ØNULL¡£²ÎÊýN½âÊÍΪһ¸öÕûÊý£¬µ«ÊÇ¿ÉÒÔÖ¸¶¨ÎªÒ»¸öÕûÊý»òÒ»¸ö×Ö·û´®¡£×îС»ùÊÇ2ÇÒ×î´óµÄ»ùÊÇ36¡£Èç¹ûto_baseÊÇÒ»¸ö¸ºÊý£¬N±»ÈÏΪÊÇÒ»¸öÓзûºÅÊý£¬·ñÔò£¬N±»µ±×÷ÎÞ·ûºÅÊý¡£ CONVÒÔ64λµã¾«¶È¹¤×÷¡£
mysql> select CONV("a",16,2);
-> '1010'
mysql> select CONV("6E",18,8);
-> '172'
mysql> select CONV(-17,10,-18);
-> '-H'
mysql> select CONV(10+"10"+'10'+0xa,10,10);
-> '40'
BIN(N) ·µ»Ø¶þ½øÖÆÖµNµÄÒ»¸ö×Ö·û´®±íʾ£¬ÔÚ´ËNÊÇÒ»¸ö³¤ÕûÊý(BIGINT)Êý×Ö£¬ÕâµÈ¼ÛÓÚCONV(N,10,2)¡£Èç¹ûNÊÇNULL£¬·µ»ØNULL¡£
mysql> select BIN(12);
-> '1100'
OCT(N) ·µ»Ø°Ë½øÖÆÖµNµÄÒ»¸ö×Ö·û´®µÄ±íʾ£¬ÔÚ´ËNÊÇÒ»¸ö³¤ÕûÐÍÊý×Ö£¬ÕâµÈ¼ÛÓÚCONV(N,10,8)¡£Èç¹ûNÊÇNULL£¬·µ»ØNULL¡£
mysql> select OCT(12);
-> '14'
HEX(N) ·µ»ØÊ®Áù½øÖÆÖµNÒ»¸ö×Ö·û´®µÄ±íʾ£¬ÔÚ´ËNÊÇÒ»¸ö³¤ÕûÐÍ(BIGINT)Êý×Ö£¬ÕâµÈ¼ÛÓÚCONV(N,10,16)¡£Èç¹ûNÊÇNULL£¬·µ»ØNULL¡£
mysql> select HEX(255);
-> 'FF'
CHAR(N,...) CHAR()½«²ÎÊý½âÊÍΪÕûÊý²¢ÇÒ·µ»ØÓÉÕâЩÕûÊýµÄASCII´úÂë×Ö·û×é³ÉµÄÒ»¸ö×Ö·û´®¡£NULLÖµ±»Ìø¹ý¡£
mysql> select CHAR(77,121,83,81,'76');
-> 'MySQL'
mysql> select CHAR(77,77.3,'77.3');
-> 'MMM'
CONCAT(str1,str2,...) ·µ»ØÀ´×ÔÓÚ²ÎÊýÁ¬½áµÄ×Ö·û´®¡£Èç¹ûÈκβÎÊýÊÇNULL£¬·µ»ØNULL¡£¿ÉÒÔÓг¬¹ý2¸öµÄ²
Ïà¹ØÎĵµ£º
¶Ïµç»ò·ÇÕý³£¹Ø»ú¶øµ¼ÖÂMySQL(ºÍPHP´îÅäÖ®×î¼Ñ×éºÏ)Êý¾Ý¿â³öÏÖ´íÎóÊǷdz£³£¼ûµÄÎÊÌâ¡£ÓÐÁ½ÖÖ·½·¨£¬Ò»ÖÖ·½·¨Ê¹ÓÃMySQL(ºÍPHP´îÅäÖ®×î¼Ñ×éºÏ)µÄcheck tableºÍrepair table µÄsqlÓï¾ä£¬ÁíÒ»ÖÖ·½·¨ÊÇʹÓÃMySQL(ºÍPHP´îÅäÖ®×î¼Ñ×éºÏ)ÌṩµÄ¶à¸ömyisamchk, isamchkÊý¾Ý¼ì²â»Ö¸´¹¤¾ß¡£Ç°ÕßʹÓÃÆðÀ´±È½Ï¼ò±ã¡£ÍƼöʹÓá£
1. ......
mysql ½ØÈ¡Ä³Ò»¸öʱ¼ä(datetimeÀàÐÍ)µÄÈÕÆÚ£º
·½·¨1£ºselect date(row_name) from table_name where row = row1;
·½·¨2£ºselect left(row_name, 10) from table_name where row = row1;
·½·¨3£ºselect cast(row_name as char[10]) from table_name where row = row1;
È¡µÃij¸öÈÕÆÚµÄtime_tÊýÖµ£ºselect unix_times ......
http://hi.baidu.com/xuwanbest/blog/item/193fd93dda509303bba167e3.html
http://wangdei.javaeye.com/blog/214265
¹ØÓÚ MySQL µ÷ÓÅ
ÓÐ 3 ÖÖ·½·¨¿ÉÒÔ¼Ó¿ì MySQL ·þÎñÆ÷µÄÔËÐÐËÙ¶È£¬Ð§Âʴӵ͵½¸ßÒÀ´ÎΪ£º
Ìæ»»ÓÐÎÊÌâµÄÓ²¼þ¡£
¶Ô MySQL ½ø³ÌµÄÉèÖýøÐе÷ÓÅ¡£
¶Ô²éѯ½øÐÐÓÅ»¯¡£
Ç¨ÒÆµ½ DB2
ÄúÕýÔÚѰÕÒÒ»Öָɾ»À ......
ǰһƪÎÄÕÂÖÐ˵µ½ÁËLOADÃüÁÕâÀï¾ÍÀ´ÏêϸµÄ¸ø×Ô¼º£¬Ë³±ãÒ²¸ø´ó¼Ò½²½âÏÂLOADÃüÁîºÍÅú´¦ÀíµÄÊý¾Ýµ¼È빦ÄÜ¡£ÓõÄʱºò¸Ð¾õMySQLÓÃÆðÀ´ÕæµÄ±È½Ï×ÌÈ󡣡£¡£¡£
Åú´¦Àíµ¼ÈëÎļþ£¬´ÓsqlÎļþµ¼ÈëÊý¾Ýµ½Êý¾Ý¿âÖÐ £¬Åú´¦ÀíÊÇÒ»Öַǽ»»¥Ê½ÔËÐÐmysql³ÌÐòµÄ·½·¨£¬ ......
Mysql Öж¨Òå×ֶκóµÄÊý¾ÝµÄÓô¦£º
int(1)ºÍint(10)ËÆºõûÓÐʲô²î±ð£¬¶¼±íʾ×î´óËĸö×Ö½ÚµÄÕûÐÍÊý¾Ý¡£
ÀýÈ綨ÒåÒ»¸öÃû×ÖΪtestµÄ±í:
DROP TABLE IF EXISTS `test`;
CREATE TABLE `test` (
`id` int(1) NOT NULL,
`ids` int(10) default NULL,
`c` char(1) default NULL,
`cs` ......