尊龙凯时人生就是搏

sqlÖÐisnullÊÇʲôÒâ˼

isnull º¯ÊýÓÃÓÚ¼ì²é±í´ïʽÊÇ·ñΪ null £¬ÊÇÔò·µ»ØÖ¸¶¨µÄÌæ»»Öµ £¬²»È»·µ»Ø±í´ïʽ×Ô¼º¡£Ö÷ÒªÓÃ;°üÀ¨£º1. Ìæ»» null ֵΪ·Ç null Öµ£»2. ×èÖ¹Êý¾Ýת»»¹ýʧ£»3. ÏÔʾÓÐÒâÒåµÄÖµ¡£

ISNULL º¯Êý¼°ÆäÓÃ;

ISNULL º¯ÊýÊÇÒ»¸ö SQL º¯Êý £¬ÓÃÓÚ¼ì²é¸ø¶¨±í´ïʽÊÇ·ñΪ NULL¡£ÈôÊDZí´ïʽΪ NULL £¬Ôò·µ»ØÖ¸¶¨µÄÌæ»»Öµ£»²»È» £¬·µ»Ø±í´ïʽ×Ô¼º¡£

Óï·¨£º

ISNULL(expression, replacement_value)

µÇ¼ºó¸´ÖÆ

²ÎÊý£º

expression£ºÒª¼ì²éµÄ±í´ïʽ¡£

replacement_value£ºÈôÊÇ expression Ϊ NULL £¬Ôò·µ»ØµÄÌæ»»Öµ¡£

ÓÃ;£º

ISNULL º¯ÊýÖ÷ÒªÓÃÓÚ´¦Àí NULL Öµ £¬±ÜÃâ·ºÆðÊý¾ÝÍêÕûÐÔÎÊÌâ¡£ÒÔÏÂÊÇ ISNULL º¯ÊýµÄ³£¼ûÓÃ;£º

Ìæ»» NULL ֵΪ·Ç NULL Öµ£ºISNULL º¯Êý¿ÉÒÔ½« NULL ÖµÌ滻ΪԤ½ç˵µÄ·Ç NULL Öµ £¬È·±£Êý¾ÝÍêÕûÐÔ¡£

×èÖ¹Êý¾Ýת»»¹ýʧ£ºÔÚijЩÇéÐÎÏ £¬NULL ÖµÎÞ·¨×ª»»ÎªÆäËûÊý¾ÝÀàÐÍ £¬ÀýÈçÔÚ¾ÙÐÐÊýѧÔËËãʱ¡£ISNULL º¯Êý¿ÉÒÔ½« NULL ÖµÌ滻Ϊ 0 µÈռλ·û £¬´Ó¶ø×èֹת»»¹ýʧ¡£

ÏÔʾÓÐÒâÒåµÄÖµ£º¹ØÓÚijЩ±¨±í»òÓ¦ÓóÌÐò £¬ÏÔʾ NULL Öµ¿ÉÄܲ»¶ÔÊÊ»ò²»Àû±ã¡£ISNULL º¯Êý¿ÉÒÔ½« NULL ÖµÌ滻Ϊ¸ü¾ßÒâÒåµÄÎı¾»òÊý×Ö £¬ÀýÈç “Î´Öª” »ò “-1″¡£

ʾÀý£º

ÒÔÏÂʾÀý½«Îª NULL µÄ Name ÁÐÌ滻Ϊ “Unknown”£º

SELECT ISNULL(Name, 'Unknown') AS Name
FROM table_name;

µÇ¼ºó¸´ÖÆ

ÒÔÏÂʾÀý½«Îª NULL µÄ Amount ÁÐÌ滻Ϊ 0£º

SELECT ISNULL(Amount, 0) AS Amount
FROM table_name;

µÇ¼ºó¸´ÖÆ

×¢ÖØ£º

ISNULL º¯Êý½öÊÊÓÃÓÚµ¥¸ö±í´ïʽ¡£ÈôÊDZí´ïʽ°üÀ¨×ÓÅÌÎÊ»ò JOIN £¬Ôò¿ÉÄÜÐèҪʹÓÃÆäËûº¯Êý£¨ÀýÈç COALESCE£©¡£

ISNULL º¯ÊýµÄÌæ»»Öµ¿ÉÒÔÊÇÈκÎÊý¾ÝÀàÐÍ¡£

ÈôÊDZí´ïʽΪ·Ç NULL £¬Ôò ISNULL º¯Êý½«Ô­Ñù·µ»Ø¸Ã±í´ïʽ¡£

ÒÔÉϾÍÊÇsqlÖÐisnullÊÇʲôÒâ˼µÄÏêϸÄÚÈÝ £¬¸ü¶àÇë¹Ø×¢±¾ÍøÄÚÆäËüÏà¹ØÎÄÕ£¡

ÃâÔð˵Ã÷£ºÒÔÉÏչʾÄÚÈÝȪԴÓÚÏàÖúýÌå¡¢ÆóÒµ»ú¹¹¡¢ÍøÓÑÌṩ»òÍøÂçÍøÂçÕûÀí £¬°æȨÕùÒéÓë±¾Õ¾ÎÞ¹Ø £¬ÎÄÕÂÉæ¼°¿´·¨Óë¿´·¨²»´ú±í尊龙凯时人生就是搏ÂËÓÍ»úÍø¹Ù·½Ì¬¶È £¬Çë¶ÁÕß½ö×ö²Î¿¼¡£±¾ÎĽӴýתÔØ £¬×ªÔØÇë˵Ã÷À´ÓÉ¡£ÈôÄúÒÔΪ±¾ÎÄÇÖÕ¼ÁËÄúµÄ°æȨÐÅÏ¢ £¬»òÄú·¢Ã÷¸ÃÄÚÈÝÓÐÈκÎÉæ¼°ÓÐÎ¥¹«µÂ¡¢Ã°·¸Ö´·¨µÈÎ¥·¨ÐÅÏ¢ £¬ÇëÄúÁ¬Ã¦ÁªÏµ尊龙凯时人生就是搏ʵʱÐÞÕý»òɾ³ý¡£

Ïà¹ØÐÂÎÅ

ÁªÏµ尊龙凯时人生就是搏

18523999891

¿É΢ÐÅÔÚÏß×Éѯ

ÊÂÇéʱ¼ä£ºÖÜÒ»ÖÁÖÜÎå £¬9:30-18:30 £¬½ÚãåÈÕÐÝÏ¢

QR code
sitemap¡¢ÍøÕ¾µØͼ