Sql Server杩炶〃鏌ヨ瀛楁涓簄ull

Posted 2021-03-23

鏍囩锛?a href='http://www.mamicode.com/so/1/%e6%95%b0%e6%8d%ae' title='鏁版嵁'>鏁版嵁   缁撴灉   鍑芥暟   鍒ゆ柇   use   out   str   rom   

杩欐槸涓€涓潙锛屽苟涓旀槸鏈夋瘨鐨勫潙銆?/p>

涓€涓嶅皬蹇冩垜灏辨帀杩涗簡杩欎釜鍧戦噷闈紝璐逛簡濂藉ぇ鐨勫姏姘旇繖鎵嶄粠鍧戦噷闈㈢埇鍑烘潵銆?/p>

璇濅笉澶氳锛屽紑濮嬪惞BB鍟︺€?/p>

涓€.绠€鍗曡璇撮亣鍒扮殑闂锛?/p>

    杩炶〃鏌ヨ锛屼竴瀵瑰銆?/p>

    鍑虹幇 int,  smalldatetime绛夐潪string绫诲瀷鐨勫瓧娈典负null銆?/span>

    鎿嶄綔濡備笅锛?/p>

    1.sql璇彞鏌ヨ锛岀粨鏋滃畬鍏ㄥ噯纭€?/p>

    2.鐩存帴鍚庡彴鑾峰彇锛岀粨鏋滄湁鐐逛笉涓€鏍凤紝鍑虹幇寮傚父銆?/p>

浜?瑙ｅ喅鍔炴硶濡備笅锛?/p>

    浣跨敤 ISNULL(value1锛?value2) 

    1銆乿alue1涓巚alue2鐨勬暟鎹被鍨嬪繀椤讳竴鑷淬€?/p>

    2銆佸鏋渧alue1鐨勫€间笉涓簄ull锛岀粨鏋滆繑鍥瀡alue1銆?/p>

    3銆佸鏋渧alue1涓簄ull锛岀粨鏋滆繑鍥瀡aule2鐨勫€笺€倂aule2鏄綘璁惧畾鐨勫€笺€?/p>

    濡傛灉鍦╯elect涓氨鏄痠snull鍙互鍒ゆ柇鏄惁鏄痭ull锛屽鏋滄槸缁欎釜榛樿鍊硷紝isnull("瀛楁鍚?锛?璁惧畾榛樿鐨勬暟鎹?)

 

    渚嬪1锛歴elect isnull(fs,6) from xuesheng where name=鈥樺紶涓夆€? 鍦ㄨ〃xuesheng涓紝fs鍒嗘暟濡傛灉涓虹┖锛岀粨鏋滆緭鍑?銆傚鏋滀笉涓虹┖锛岃緭鍑篺s鐨勫€笺€?/p>

    渚嬪2锛歋ELECT  A.UserID,

                                A.LoginName, 

                                ISNULL(B.AddTime, 0)  AS AddTime,

                                ISNULL(B.ID, 0) AS ID

    FROM      A LEFT OUTER JOIN B ON A.UserID = B.UserID

 

Mysql鐨刬fnull()鍑芥暟锛?/strong>