access里的mid函数是什么意思 access 中关于MID函数的用法
access\u91cc\u7684mid\u51fd\u6570\u662f\u4ec0\u4e48\u610f\u601dmid\u662f\u4ece\u4e2d\u95f4\u4f4d\u7f6e\u53d6\u5b50\u4e32\u51fd\u6570
\u683c\u5f0f\u5982\u4e0b\uff1a
mid\uff08\u5b57\u7b26\u4e32\uff0c\u8d77\u59cb\u4f4d\uff0c\u622a\u53d6\u7684\u4f4d\u6570\uff09
\u4f8b\u5982\uff1a
mid\uff08\u201cabcdef\u201d\uff0c2\uff0c3\uff09
\u7ed3\u679c\u662fbcd
Mid \u51fd\u6570\u8fd4\u56de\u4e00\u4e2a Variant (String) \u503c\uff0c\u5176\u4e2d\u5305\u542b\u5b57\u7b26\u4e32\u4e2d\u6307\u5b9a\u6570\u91cf\u7684\u5b57\u7b26\u3002
\u82e5\u8981\u786e\u5b9a\u5b57\u7b26\u4e32\u4e2d\u7684\u5b57\u7b26\u6570\uff0c\u8bf7\u4f7f\u7528Len\u51fd\u6570\u3002\u6ce8\u610f: \u5c06MidB\u51fd\u6570\u4e0e\u5b57\u7b26\u4e32\u4e2d\u5305\u542b\u7684\u5b57\u8282\u6570\u636e\u7ed3\u5408\u4f7f\u7528\uff0c\u5982\u540c\u5728\u53cc\u5b57\u8282\u5b57\u7b26\u96c6\u8bed\u8a00\u4e2d\u4e00\u6837\u3002 \u53c2\u6570\u6307\u5b9a\u5b57\u8282\u6570\uff0c\u800c\u4e0d\u662f\u6307\u5b9a\u5b57\u7b26\u6570\u3002
\u67e5\u8be2\u793a\u4f8b
\u4ece ProductSales \u4e2d\u9009\u62e9 "ProductID"\u3001"Mid" \uff08ProductID\uff0c5\uff09\u4f5c\u4e3a\u8868\u8fbe\u5f0f1
\u7ed3\u679c\uff1a\u8fd4\u56de\u4ece\u5b57\u7b26\u4f4d\u7f6e5\u5f00\u59cb\u7684 "\u4ea7\u54c1 Id" \u548c "\u4ea7\u54c1 Id" \u90e8\u5206\uff0c\u5e76\u5728 "\u5217\u8868\u8fbe\u5f0f 1" \u4e2d\u663e\u793a\u7ed3\u679c\u3002
\u4ece ProductSales \u4e2d\u9009\u62e9 "ProductID"\u3001"Mid" \uff08ProductID\u30015\u30014\uff09\u4f5c\u4e3a testMid\u3002
\u7ed3\u679c\uff1a\u8fd4\u56de\u4ece\u5b57\u7b26\u4f4d\u7f6e5\u5f00\u59cb\u7684 "ProductID" \u548c ProductID \u90e8\u5206\uff0c\u5176\u4e2d\u5305\u542b4\u4e2a\u5b57\u7b26\u5e76\u5728\u5217 testMid \u4e2d\u663e\u793a\u7ed3\u679c\u3002
\u6269\u5c55\u8d44\u6599
access\u53d6\u5b57\u7b26\u4e32\u5b57\u6bb5\u7684\u51fd\u6570mid\u548cSQL\u4e2dsubstring\u51fd\u6570\u4e00\u6837\u7684\u4f5c\u7528\u3002
SQL \u4e2d\u7684 substring \u51fd\u6570\u662f\u7528\u6765\u6293\u51fa\u4e00\u4e2a\u680f\u4f4d\u8d44\u6599\u4e2d\u7684\u5176\u4e2d\u4e00\u90e8\u5206\u3002\u8fd9\u4e2a\u51fd\u6570\u7684\u540d\u79f0\u5728\u4e0d\u540c\u7684\u8d44\u6599\u5e93\u4e2d\u4e0d\u5b8c\u5168\u4e00\u6837\uff1a
MySQL: SUBSTR( ), SUBSTRING( )
Oracle: SUBSTR( )
SQL Server: SUBSTRING( )
\u6700\u5e38\u7528\u5230\u7684\u65b9\u5f0f\u5982\u4e0b (\u5728\u8fd9\u91cc\u6211\u4eec\u7528 SUBSTR( ) \u4e3a\u4f8b)\uff1a
SUBSTR (str, pos)
\u7531 \u4e2d\uff0c\u9009\u51fa\u6240\u6709\u4ece\u7b2c \u4f4d\u7f6e\u5f00\u59cb\u7684\u5b57\u5143\u3002\u8bf7\u6ce8\u610f\uff0c\u8fd9\u4e2a\u8bed\u6cd5\u4e0d\u9002\u7528\u4e8e SQL Server \u4e0a\u3002
SUBSTR (str, pos, len)
\u7531 \u4e2d\u7684\u7b2c \u4f4d\u7f6e\u5f00\u59cb\uff0c\u9009\u51fa\u63a5\u4e0b\u53bb\u7684 \u4e2a\u5b57\u5143\u3002
格式如下：
mid（字符串，起始位，截取的位数）
例如：
mid（“abcdef”，2，3）
结果是bcd
这个函数的作用就是取字符串中间的字符
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绛旓細access涓鏈変釜mid鍑芥暟锛屽彲浠ョ敤鏉ユ埅鍙栧瓧绗︿覆鎴栬呮棩鏈熴俿elect * from 琛ㄥ悕 where mid([TestTime],5,10) ='04/19/2013'鍏朵腑锛5浠ｈ〃鎴彇鐨勫紑濮嬩綅缃紝浠庡乏鏁帮紝10浠ｈ〃鎴彇鐨勯暱搴︺傛暟鎹簱鐨勬棩鏈熷尯闂存煡璇㈡湁涓ょ鎯呭喌锛1锛氭煡璇㈢粰瀹氭椂闂村湪寮濮嬫椂闂村垪涓庣粨鏉熸椂闂村垪鑼冨洿涓暟鎹紱2锛氭煡璇㈡棩鏈熷垪鍦ㄥ紑濮嬫椂闂村垪涓庣粨鏉...
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绛旓細鍦∕S Access SQL鍑芥暟涓紝Scalar鍑芥暟鏄涓绉嶇壒娈婄被鍨嬬殑鍑芥暟锛屽畠涓昏鐢ㄤ簬澶勭悊鍗曚釜鍊肩殑杩愮畻鎴栬浆鎹備妇涓緥瀛愶紝UCASE(c)鍑芥暟鑳藉灏嗚緭鍏ョ殑鏌愪釜鍩涓殑鏂囨湰鍏ㄩ儴杞崲涓哄ぇ鍐欏舰寮忥紝杩欏浜庡鐞嗗瓧绗︿覆鏃剁殑澶у皬鍐欒浆鎹㈤潪甯告湁鐢ㄣ傜浉鍙嶏紝LCASE(c)鍑芥暟鍒欑敤浜庡皢鏂囨湰杞崲涓哄皬鍐欙紝纭繚鏂囨湰鐨勪竴鑷存у拰鍙鎬с傚浜庢枃鏈鐞嗙殑绮剧粏...
绛旓細select 鐝,浜ч噺,鐢熶骇宸ユ椂,浜ч噺/鐢熶骇宸ユ椂*12/(1000*60*12) AS 寮鏈烘晥鐜,鐢熶骇鏃ユ湡 from 鐢熶骇鏃ユ姤 where 鐝 like '%5%' union all select 鐝,浜ч噺,鐢熶骇宸ユ椂,浜ч噺/鐢熶骇宸ユ椂*12/(1600*60*12) AS 寮鏈烘晥鐜,鐢熶骇鏃ユ湡 from 鐢熶骇鏃ユ姤 where 鐝 not like '%5%'...
