尊龙凯时人生就是搏

ÔÚsqlÖбí´ïij¸öÊôÐÔΪ¿ÕµÄº¯Êý

ÓÃÓÚ±í´ïÊôÐÔΪ¿ÕµÄ sql º¯ÊýÊÇ is null¡£Ëü¼ì²éij¸öÊôÐÔµÄÖµÊÇ·ñΪ null £¬²¢·µ»Ø true£¨Îª¿Õ£©»ò false£¨²»Îª¿Õ£©¡£is null ¿ÉÓëÆäËûÔËËã·ûÍŽáʹÓà £¬Èç not is null£¨²»Îª¿Õ£©ºÍ is null or attribute_name = ”£¨Îª¿Õ»òΪ¿Õ×Ö·û´®£©¡£¸Ãº¯Êý¶Ô null ÖµÃô¸Ð £¬ÓÐÖúÓÚÈ·±£Êý¾ÝÍêÕûÐÔ¡£

ÔÚ SQL Öбí´ïÊôÐÔΪ¿ÕµÄº¯Êý

ʲôº¯Êý¿ÉÒÔ±í´ïÊôÐÔΪ¿Õ£¿

ÓÃÓÚ±í´ïÊôÐÔΪ¿ÕµÄ SQL º¯ÊýÊÇ IS NULL¡£

ÔõÑùʹÓà IS NULL º¯Êý£¿

IS NULL º¯ÊýÓÃÓÚ¼ì²éij¸öÊôÐÔµÄÖµÊÇ·ñΪ¿Õ£¨¼´Îª NULL£©¡£ËüµÄÓï·¨ÈçÏ£º

IS NULL(attribute_name)

µÇ¼ºó¸´ÖÆ

ÆäÖÐ £¬attribute_name ÊÇÒª¼ì²éÆäÊÇ·ñΪ¿ÕµÄÊôÐÔÃû¡£

IS NULL º¯ÊýÔõÑùÊÂÇ飿

IS NULL º¯Êý·µ»ØÒ»¸ö²¼¶ûÖµ£ºTRUE ÌåÏÖÊôÐÔΪ¿Õ £¬FALSE ÌåÏÖÊôÐÔ²»Îª¿Õ¡£ÀýÈ磺

SELECT * FROM table_name WHERE attribute_name IS NULL;

µÇ¼ºó¸´ÖÆ

´ËÅÌÎʽ«·µ»Ø table_name ±íÖÐËùÓÐÊôÐÔ attribute_name Ϊ¿ÕµÄÐС£

ÆäËûʹÓÃÒªÁ죺

IS NULL º¯ÊýÒ²¿ÉÒÔÓëÆäËûÂß¼­ÔËËã·ûÍŽáʹÓá£ÀýÈ磺

NOT IS NULL ¼ì²éÊôÐÔÊÇ·ñ²»Îª¿Õ¡£

IS NULL OR attribute_name = ” ¼ì²éÊôÐÔÊÇ·ñΪ¿Õ»òΪ¿Õ×Ö·û´®¡£

×¢ÖØÊÂÏ

IS NULL º¯Êý¶Ô NULL ÖµÃô¸Ð £¬ÕâÒâζ×ÅËüÖ»Äܼì²é NULL Öµ £¬¶ø²»¿É¼ì²éÆäËûÀàÐ͵ĿÕÖµ £¬ÀýÈç¿Õ×Ö·û´®»ò 0¡£

IS NULL º¯Êý¹ØÓÚÈ·±£Êý¾ÝÍêÕûÐԺʹ¦ÀíȱʧֵºÜÊÇÓÐÓá£

ÒÔÉϾÍÊÇÔÚsqlÖбí´ïij¸öÊôÐÔΪ¿ÕµÄº¯ÊýµÄÏêϸÄÚÈÝ £¬¸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