尊龙凯时人生就是搏

sqlÖÐllÊÇʲôÒâ˼

sql ÖÐµÄ ll ÌåÏÖÁÐÁбí (list of lists)£¬ÓÃÓÚÔÚ select Óï¾äÖн«¶à¸ö×ÓÅÌÎÊ»òÅÉÉú±íµÄЧ¹û×éºÏ³Éµ¥¸öЧ¹û¼¯£¬Ìá¸ß´úÂë¿É¶ÁÐÔ¡¢ÐÔÄܺÍÄ£¿é»¯¡£

LLÔÚSQLÖеļÄÒå

ÔÚSQLÖУ¬LL´ú±íÁÐÁбí (list of lists)¡£ËüÊÇÖ¸SELECTÓï¾äÖзµ»ØЧ¹û¼¯Ê±£¬Ê¹ÓÃÔ²À¨ºÅÀ¨ÆðÀ´µÄ×ÓÅÌÎÊ»òÅÉÉú±íµÄЧ¹û¡£

ÔõÑùʹÓÃLL

LLͨ³£ÓÃÓÚ½«¶à¸öÅÌÎÊЧ¹û×éºÏ³Éµ¥¸öЧ¹û¼¯¡£¿ÉÒÔͨ¹ýÒÔÏ·½·¨Ê¹ÓÃLL£º

SELECT * FROM (
  SELECT column1 FROM table1
  UNION
  SELECT column2 FROM table2
) AS ll;

µÇ¼ºó¸´ÖÆ

ÉÏÃæµÄÅÌÎʽ«·µ»ØÀ´×Ôtable1ºÍtable2µÄcolumn1ºÍcolumn2µÄ×éºÏЧ¹û¼¯¡£

LLµÄÀûÒæ

ʹÓÃLL¿ÉÒÔ´øÀ´ÒÔÏÂÀûÒ棺

Ìá¸ß¿É¶ÁÐÔ£ºÍ¨¹ý½«ÖØ´óÅÌÎʲð·ÖΪ¶à¸ö½ÏСµÄÅÌÎÊ£¬¿ÉÒÔÌá¸ß´úÂëµÄ¿É¶ÁÐÔ¡£

Ìá¸ßÐÔÄÜ£º¹ØÓÚijЩÅÌÎÊ£¬Ê¹ÓÃLL¿ÉÒÔÓÅ»¯ÅÌÎÊÐÔÄÜ¡£

ʵÏÖÄ£¿é»¯£ºLL¿ÉÒÔ½«ÅÌÎÊÆÊÎöΪ¿ÉÖØÓõÄ×é¼þ£¬´Ó¶øʵÏÖÄ£¿é»¯¡£

ʾÀý

ÒÔÏÂʾÀý˵Ã÷ÎúÔõÑùʹÓÃLL£º

-- ÅÌËã×ÜÏúÊÛ¶î
SELECT SUM(sales) AS total_sales
FROM (
  SELECT SUM(sales) AS sales
  FROM orders
  GROUP BY customer_id
);

µÇ¼ºó¸´ÖÆ

Õâ¸öÅÌÎʽ«ÅÌËãËùÓпͻ§µÄ×ÜÏúÊ۶²¢ÒÔLLµÄÐÎʽ·µ»ØЧ¹û¡£

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

ÃâÔð˵Ã÷£ºÒÔÉÏչʾÄÚÈÝȪԴÓÚÏàÖúýÌå¡¢ÆóÒµ»ú¹¹¡¢ÍøÓÑÌṩ»òÍøÂçÍøÂçÕûÀí£¬°æȨÕùÒéÓë±¾Õ¾Î޹أ¬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»ÖÁÖÜÎ壬9:30-18:30£¬½ÚãåÈÕÐÝÏ¢

QR code
sitemap¡¢ÍøÕ¾µØͼ