Çë½Ì:ÔõÑùÅжÏÒ»¸ö±íÊÇ·ñΪ¿Õ±í

T-SQL´úÂ룺IF (NOT EXISTS(SELECT * FROM [±íÃû])) PRINT 'ÕâÊÇÒ»¸ö¿Õ±í'½âÊÍ£ºEXISTS() //Èç¹û²éѯµ½Êý¾Ý·µ»Øtrue, ...


ÈçºÎÅжÏSQL SERVER±íÖÐ×Ö¶ÎΪ¿Õ?

\x0d\x0aÒòΪÊÇdatetimeÀàÐÍ£¬ËùÒÔ¿ÕÖ»ÄÜÊÇNULLµÄÇé¿ö£¬²»»á³öÏÖ''Çé¿ö£¬¶øÇÒ''µÄÇé¿öÖ»ÄÜÊÇ×Ö·ûÐͲſÉÄÜ»áÓеÄÇé¿ö¡£A001='...


ÅжÏMySQL±íµ¥ÊÇ·ñΪ¿Õ¿ÉÓÃemptyº¯Êý

ÅжÏMySQL±íµ¥ÊÇ·ñΪ¿Õ ·½·¨Ò»:$sql=select*formabc$result=MySQL_query($sql);$row=MySQL_fetch_array($result);if(empty($ro...


sql²éѯÔõôÅжϽá¹ûÊDz»ÊÇΪ¿Õ

·½·¨Ò»£º°ÑÕâ¸ö²éѯµÄ½á¹û·Åµ½Êý¾Ý¼¯ÖÐ È»ºóÓÃÒ»¸öifÅжϷµ»ØµÄÊý¾Ý¼¯¼Ç¼ÊýÊÇ·ñ<=0 Èç¹û<=0µÄ»°Ôò½á¹ûΪ¿Õ¡£·½·¨¶þ£ºÖ±½Ó°ÑS...


sql Óï¾ä²é³öµÄÊý¾ÝΪ¿Õ,ÔõôÓøöifÓï¾äÅжÏ,È»ºó×÷³ö´¦Àí...

select nvl(sum(price),0),userName from food join diningcar on food.foodId=diningcar.foodId join users on diningcar.us...


sqlÓï¾ä²é³öµÄÊý¾ÝΪ¿Õ,ÔõôÓøöifÓï¾äÅжÏ,È»ºó×÷³ö´¦Àí...

¿ÉÒÔʵÏÖ£¬ÒÔsql serverΪÀý¿´£ºif not exists(select userName from food join diningcar on food.foodId=diningcar.foodId ...


...×Ó¾äÖÐÅжÏÒ»¸ö±í´ïʽµÄÖµÊÇ·ñΪ¿ÕÖµ,Ó¦¸ÃʹÓÃʲôÔËËã·û...

ʹÓÃis nullɸѡcol_nameΪ¿ÕµÄÇé¿ö£»Àý£ºselect * from table_name where col_name is null;ʹÓÃis not nullɸѡcol_name·Ç¿Õ...


ÈçºÎÅжÏSQL SERVER±íÖÐ×Ö¶ÎΪ¿Õ

sql server ÖÐʹÓà is null »ò is not null À´´¦ÀíÁеĿÕÖµ¡£Ó﷨Ϊ£ºÁÐÃû is null (×Ö¶ÎΪ¿Õ·µ»Øtrue ,²»Îª¿Õ·µ»Ø false)...


sqlµÄwhereÌõ¼þÖÐÊÇ·ñnullÏà¹ØÌõ¼þÔõôд

sqlµÄwhereÌõ¼þÅжÏÖµÊÇ·ñΪnull£¬¿ÉÒÔÖ±½ÓÓëNULL½øÐбȽϡ£Àý£ºselect * from a where e=null;--¼ìË÷...


vbÊý¾Ý¿âsql²éѯÅжϽá¹ûÊÇ·ñΪ¿Õ

If data1.Recordset.RecordCount > 0 then ¡®ÈôÊǿյĻ° Msgbox "No Data Record to be found"Else ¡®Èô²»ÊǿյĻ° End If...


Ïà¹ØËÑË÷

ÈÈÃÅËÑË÷