SQL查询语句问题 SQL语句查询不等于怎么查不出来？
sql\u67e5\u8be2\u8bed\u53e5Like \u7684\u95ee\u9898SQL\u91cc\u9762\u6a21\u7cca\u5339\u914d\u8981\u7528%\uff0c\u6240\u4ee5\u5fc5\u987b\u662f\u2018\u54c1\u724c%\u2019
\u4f60\u53d7\u6b63\u5219\u8868\u8fbe\u5f0f\u7684\u5f71\u54cd\u4e86
\u4e00\u822c\u67e5\u8be2\u4e0d\u51fa\u5c31\u662f\u4e0d\u7b49\u4e8e\u67d0\u503c\u65f6\u6ca1\u6709\u6570\u636e\uff0c\u5e76\u4e0d\u4e00\u5b9a\u4ee3\u8868\u8bed\u53e5\u9519\u8bef\u3002
\u5728SQL\u8bed\u53e5\u4e2d\u4e0d\u7b49\u4e8e\u6709\u4e24\u79cd\u7528\u6cd5\uff0c\u4e00\u79cd\u662f""\uff0c\u4e00\u79cd\u662f"!="(\u5747\u4e0d\u542b\u5f15\u53f7)\u3002
1\u3001\u521b\u5efa\u6d4b\u8bd5\u8868\uff0c\u63d2\u5165\u6570\u636e\uff1a
create table test(id int,name varchar(10)); insert into test values (1,'\u5f20\u4e09');insert into test values (2,'\u674e\u56db');
2\u3001\u6267\u884c\u7b2c\u4e00\u79cd\u64cd\u4f5c""
select * from test where id1; \u7ed3\u679c\u5982\u56fe\uff1a
3\u3001\u6267\u884c\u7b2c\u4e8c\u79cd\u64cd\u4f5c"!="
select * from test where id1; \u7ed3\u679c\u5982\u56fe\uff1a
使用如下SQL语句查询出表中外键约束名称：
select name
from sys.foreign_key_columns f join sys.objects o on f.constraint_object_id=o.object_id
where f.parent_object_id=object_id('表名')
alter table 表名 drop constraint 外键约束名
绛旓細'' 2涓崟寮曞彿琛ㄧず涓涓 ' 鍗曞紩鍙, 杩欐槸杞箟瀛楃鐨勫啓娉, 鍥犱负 ' 鍗曞紩鍙锋槸璇硶涓殑鏍囪瘑绗︽蹇 "" 2涓弻寮曞彿绫讳技2涓崟寮曞彿鐨勬剰璇 闂涓 & 瀛楃涓茶繛鎺 A&B 鐩稿綋浜2涓彉閲忕殑鍊艰繛鎺 A=abc B=def A&B = abcdef 闂鍥 鍦SQL涓敤瀛楃涓插墠鍚庡姞#琛ㄧず璇ュ瓧绗︿覆涓烘棩鏈熸牸寮 闂浜 鍦⊿QL涓〃...
绛旓細CREATE TABLE #test ( code varchar(20) );goINSERT INTO #test VALUES('1');INSERT INTO #test VALUES('1.1');INSERT INTO #test VALUES('1.20');INSERT INTO #test VALUES('1.1.1');INSERT INTO #test VALUES('1.1.2');INSERT INTO #test VALUES('1.1.3');INSERT INTO #te...
绛旓細杩欎釜鏌ヨ灏嗕細鍦‵_ORA_FEEDBACKDATE灏忎簬'2023-01-01'鏃讹紝灏哫XX鐨勫兼斁鍏'23骞村墠宸ユ椂'杩欎釜瀛楁锛屽綋F_ORA_FEEDBACKDATE澶т簬鎴栫瓑浜'2023-01-01'鏃讹紝灏哫X鐨勫兼斁鍏'浜屼笁骞村悗宸ユ椂'杩欎釜瀛楁銆傛敞鎰忚繖閲岀殑XXX鍜孹X搴旇鏄綘鐨勫疄闄呭瓧娈垫垨鑰呰绠楄〃杈惧紡銆傚鏋滄棩鏈熶笉鍦ㄨ繖涓寖鍥达紝閭ｄ箞瀵瑰簲鐨勫瓧娈靛皢涓篘ULL銆
绛旓細ORDER BY CustomerID DESC;鏌ヨ鍚勪釜鍩庡競鐨勫鎴锋绘暟锛岀粨鏋滄樉绀篊ity(鍩庡競鍚嶇О)鍙夾mount锛堝鎴锋暟閲忥級SELECT City, COUNT( 1 ) AS Amount FROM 琛 GROUP BY City;鏌ヨ瀹㈡埛鎬讳汉鏁板ぇ浜3浜虹殑鍩庡競锛岀粨鏋滄樉绀篊ity(鍩庡競鍚嶇О)鍙夾mount锛堝鎴锋暟閲忥級SELECT City, COUNT( 1 ) AS Amount FROM 琛...
绛旓細鍦ㄨ鍙ヤ腑娌℃寚鏄庡摢涓〃銆傛墍浠ユ槸unknowncolumn锛孲QL涓嶇煡閬撴槸鍝釜琛ㄧ殑瀛楁銆傚湪妫鏌SQL璇彞瀹屽叏鏃犺鍚庯紝鍙互妫鏌ヤ笅琛ㄤ腑鐨勬暟鎹被鍨嬭缃垨鑰呭瓧绗︾紪鐮佹牸寮忥紝姣斿鍦ㄥ嚭鐜拌繖涓敊璇椂锛屽父甯稿洜涓烘暟鎹簱浣跨敤鐨勬槸gbk鏍煎紡锛屼絾鏄瓧娈垫槸utf8缂栫爜鏍煎紡鐨勶紝琛ㄤ腑瀛楁缂栫爜鏍煎紡涓嶅悓锛屽鑷翠簡杩欎釜閿欒銆
绛旓細--闂1(鎴戞湁涓涓枒闂綘杩欎釜闇姹備細鍑虹幇缂栧彿閲嶅鎶)INSERT INTO books(book_id,book_name,au_id,type,price,qty)SELECT book_id+1000,book_name,au_id,type,price,0 FROM books WHERE book_id=N --闂2 SELECT A.au_id,A.au_name,SUM(ISNULL(B.qty,0)) AS SUM_qty FROM authors A...
绛旓細鏌ヨ褰撳墠鎵鏈夊瓨鍦ㄧ敤鎴风殑鑰冨嫟鎯呭喌--涓嶇鏄惁鏈夎冨嫟璁板綍锛岄兘瑕佹妸鐢ㄦ埛鐨勬儏鍐靛垪鍑烘潵锛岀敤宸﹁繛鎺ワ紝姝ゆ椂浼氬垪鍑烘墍鏈夌敤鎴凤紝鑰屼笉瀛樺湪鑰冨嫟璁板綍鐨勭敤鎴锋樉绀轰负绌恒俿elect from users left join duty on users.u_id=duty.u_id 3.鏌ヨ鎵鏈夊瓨鍦ㄧ殑鑰冨嫟璁板綍锛屼笉绠＄敤鎴锋槸鍚﹀垹闄わ紝鐢ㄥ彸杩炴帴銆傛鏃朵細鍒楀嚭鎵鏈夎冨嫟璁板綍锛屽凡缁忓垹闄...
绛旓細鍥犱负鍏崇郴鍨嬫暟鎹簱涓嶅叧蹇冨叧绯讳腑璁板綍鐨勯『搴忋傚鏋滃笇鏈涜〃鎸夐『搴忥紝缁欒〃涓涓富閿傚彲浠ュ厛鐢╥dentity鍑芥暟鍒嗛厤琛屽彿缁欐瘡琛岋紝鐒跺悗杈撳叆鍒颁竴涓复鏃惰〃銆俿elect count3, identity(int,1,1) as rn into #c from 琛 鐒跺悗锛鏌ユ壘鏈鍚庝竴鏉¤褰(鍊掓暟绗竴琛)銆俿elect top 1 count3 from #c order by rn desc ...
绛旓細鏄繖鏍风殑鍦SQL閲屽瓧绗﹀瀷鍙兘鐢ㄥ崟寮曞彿锛屽弻寮曞彿鏄紩鐢ㄧ殑閾炬帴鏁版嵁搴撶殑绋嬪簭閲岀殑锛屽鏋滆鐢ㄥ弻寮曞彿锛屽湪SQL閲岃鍔犱釜',瑕佹槸瑕佸姞鍗曞紩鍙蜂篃涓鏍峰墠闈㈠姞涓'鎵浠ュ氨鍙樻垚''',''浜
绛旓細SQL璇彞涓紝鍦鏌ヨ鐨剆elect鍚庣洿鎺ュ啓null鍗冲彲瀹屾垚鏌ヨ鍑轰竴涓櫄鍒楋紝骞剁敤null濉厖銆傚伐鍏凤細SqlServer 2008 R2 姝ラ锛1銆乼est琛ㄤ腑鏈夊涓嬫暟鎹細2銆佽鏌ヨ鏁翠釜琛紝骞舵坊鍔犱竴涓櫄鍒楋紝鍒楀悕涓篏ender锛屽～鍏呭间负null锛屽彲鐢ㄥ涓嬭鍙ワ細select *,null Gender from test3銆佹煡璇㈢粨鏋滀腑鍙锛岃櫄鍒楀凡鏋勫缓瀹屾瘯锛屽苟涓斾互null鍊...
