]]>
A = dao.read(id);
List<B> bList = A.getBList();
bList.clear();
B b1 = new B();
b1.setA(A);
bList.add(b1);
B b2 = new B();
b2.setA(A);
bList.add(b2);
A.
]]>
鐢變簬榪欎釜children鐨勬暟鎹茍闈為潪甯擱噸瑕侊紝涓轟簡鏂逛究錛屾垜浠湪淇敼parent鐨勬椂鍊欙紝鍋氭硶緇忓父閮芥槸
1,娓呯┖children鍏ㄩ儴鍒犱簡錛屽啀鎶婃柊鐨刢hildren鍏ㄩ儴鍔犺繘鍘匯?br /> 浠婂ぉ鏃╀笂鍋氳繖涓鏂歸潰宸ヤ綔鐨勬椂鍊欓亣鍒頒竴涓棶棰橈紝灝辨槸鍦ㄦ洿鏂皃arent鐨勬椂鍊欙紝鎶ヤ簡涓涓?br /> Don't dereference a collection with cascade="all-delete-orphan"
鐨勫紓甯革紝緇忓父涓鍗婁釜灝忔椂鐨勬煡璧勬枡鍜岃皟璇曪紝緇堜簬鎵懼埌浜嗚В鍐抽棶棰樼殑鍔炴硶
鍒氬垰寮濮嬫垜鐨勫仛娉曚負(fù)錛?br /> parent = parentService.findParentById(id);
parent.getChildren.clear();
parent.setChildren(newChildren);
parentService.updateparent(parent);
榪欐牱鍋氫竴瀹氫細(xì)鎶ュ嚭涓涓狣on't dereference a collection with cascade="all-delete-orphan"鐨勫紓甯?br /> 鍘熸潵鏄紝瀵逛簬parent鐨刢hildren榪欎釜Set錛屽畠鏈韓鏄竴涓寔涔呯殑闆嗗悎錛岃闆嗗悎瀛樺湪浜巋ibernate鐨勫璞℃睜褰撲腑錛岄氳繃
parent.setChildren(newChildren)鐨勮緗箣鍚庯紝鏈韓宸茬粡灝唒arent瀵筩hildren闆嗗悎鐨勫紩鐢ㄦ寚鍒板璞℃睜澶栫殑涓涓泦鍚堛?br /> 鍚庢潵鏌ヨ璧勬枡鍚庣殑鍋氭硶涓猴細(xì)
parent = parentService.findParentById(id);
parent.getChildren.clear();
parent.getChildren.addAll(newChildren);
parentService.updateparent(parent);
鍋氫簡鍑犳嫻嬭瘯錛岄棶棰樿В鍐熾?br /> hbm閰嶇疆濡備笅錛?br /> <set lazy="true" name="children" cascade="all,delete-orphan" inverse="true">
<key column="PARENT_ID"/>
<one-to-many class="Child"/>
</set>
鍙﹀錛宧ibernate 3宸茬粡灝哻ascade褰撲腑鐨勯夐」鍋氫簡淇敼錛岀幇鍦ㄥ凡緇忔病鏈変簡all-delete-orphan榪欎釜閫夐」錛岃櫧鐒秇ibernate
鍐呴儴榪樻槸鏀寔榪欎釜閫夐」……
]]>
mvn test -Dtest=myTest //榪愯鏌愪竴涓崟鍏冩祴璇曠被
]]>
鍦ㄦ暟鎹簱琛ㄤ腑浼?xì)鏈墭q欐牱鐨勪竴涓瓧孌電敤鏉ュ尯鍒褰曠殑灞炴э紝濡傦細(xì)鍦ㄥ鎴瘋〃涓湁涓涓瓧孌佃〃紺哄鎴風(fēng)駭鍒紝褰撹繖涓褰曚負(fù)A鏃舵槸涓綰у鎴鳳紝涓?span lang="EN-US">B鏃舵槸浜岀駭瀹㈡埛銆傚湪鐢?span lang="EN-US">hiberante鍋?span lang="EN-US">OR琛ㄧず鏃剁被鍙兘鏄繖鏍風(fēng)殑錛?/span>
public class Customer{
private String flag; //琛ㄧず瀹㈡埛鐨勭駭鍒?/span>
...
}
鐒跺悗錛屽湪紼嬪簭涓墜鍔ㄦ帶鍒?span lang="EN-US">flag鐨勫鹼紝浣嗘槸榪欐牱褰撴瘡涓駭鐨勫鎴鋒湁涓嶅悓鐨勫睘鎬ф椂Customer綾誨皢鍖呭惈鎵鏈夌駭鍒殑灞炴э紝榪欐牱涓嶆槸寰堝ソ銆?/span>
hibernate鎻愪緵涓涓?span lang="EN-US">Discriminator鏄犲皠鐨勬柟娉曪紝灝辨槸鎶婁竴涓〃鏄犲皠鎴愪笉鍚岀殑綾伙紝鏈変笉鍚岀殑灞炴с?/span>
public class Customer{
//鍖呭惈鎵鏈夌駭鍒殑鍏叡灞炴?/span>
...
}
public class CustomerA extends Customer{
//鍙寘鎷竴綰у鎴風(fēng)殑鐗規(guī)湁灞炴?/span>
}
public class CustomerB extends Customer{
//鍙寘鍚簩綰у鎴風(fēng)壒鏈夌殑灞炴?/span>
}
榪欐牱鏇寸鍚堥潰鍚戝璞＄殑鍘熷垯錛岀劧鍚庡湪hbm.xml涓繖鏍峰啓錛?/span>
<id name="id" type="int">
...
</id>
<discriminator column="flag" type="string" />
<!-- 鍏叡灞炴х殑鏄犲皠 -->
<subclass name="CustomerA" discriminator-value="A">
<!-- 涓綰у鎴風(fēng)壒鏈夊睘鎬х殑鏄犲皠 -->
</subclass>
<subclass name="CustomerB" discriminator-value="B">
<!-- 浜岀駭瀹㈡埛鐗規(guī)湁灞炴х殑鏄犲皠 -->
</subclass>
榪欐牱灝卞彲浠ュ崟鐙殑鐢?span lang="EN-US">CustomerA,CustomerB榪欐牱鐨勫疄渚嬩簡錛屽仛鏁版嵁搴撲慨鏀規(guī)椂灝變笉鐢ㄥ叧蹇?span lang="EN-US">flag瀛楁鐨勫間簡錛屼細(xì)鑷姩鐨勫姞A鎴?span lang="EN-US">B銆?/span>
濡傛灉鏄嬌鐢?span lang="EN-US">hibernate Annotation鑰屼笉鏄?span lang="EN-US">xml鏉ユ弿榪版槧璋㈠叧緋伙紝浠ｇ爜濡備笅錛?/span>
@Entity
@Table(name = "customer")
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name = "flag", discriminatorType = DiscriminatorType.STRING)
public class Customer{
}
@Entity
@DiscriminatorValue(value = "A")
public class CustomerA extends Customer{
}
@Entity
@DiscriminatorValue(value = "B")
public class CustomerB extends Customer{
}
榪欐牱灝卞彲浠ヤ簡銆?/span>
]]>
--綆鍗旵ase鍑芥暟
CASE sex
WHEN '1' THEN '鐢?/span>'
WHEN '2' THEN '濂?/span>'
ELSE '鍏朵粬' END
--Case鎼滅儲鍑芥暟
CASE WHEN sex = '1' THEN '鐢?/span>'
WHEN sex = '2' THEN '濂?/span>'
ELSE '鍏朵粬' END
榪欎袱縐嶆柟寮忥紝鍙互瀹炵幇鐩稿悓鐨勫姛鑳姐傜畝鍗旵ase鍑芥暟鐨勫啓娉曠浉瀵規(guī)瘮杈冪畝媧侊紝浣嗘槸鍜孋ase鎼滅儲鍑芥暟鐩告瘮錛屽姛鑳芥柟闈細(xì)鏈変簺闄愬埗錛屾瘮濡傚啓鍒ゆ柇寮忋?nbsp;
榪樻湁涓涓渶瑕佹敞鎰忕殑闂錛孋ase鍑芥暟鍙繑鍥炵涓涓鍚堟潯浠剁殑鍊鹼紝鍓╀笅鐨凜ase閮ㄥ垎灝嗕細(xì)琚嚜鍔ㄥ拷鐣ャ?nbsp;
--姣斿璇達(dá)紝涓嬮潰榪欐SQL錛屼綘姘歌繙鏃犳硶寰楀埌“絎簩綾?#8221;榪欎釜緇撴灉
CASE WHEN col_1 IN ( 'a', 'b') THEN '絎竴綾?/span>'
WHEN col_1 IN ('a') THEN '絎簩綾?/span>'
ELSE'鍏朵粬' END
涓嬮潰鎴戜滑鏉ョ湅涓涓嬶紝浣跨敤Case鍑芥暟閮借兘鍋氫簺浠涔堜簨鎯呫?nbsp;
涓錛屽凡鐭ユ暟鎹寜鐓у彟澶栦竴縐嶆柟寮忚繘琛屽垎緇勶紝鍒嗘瀽銆?nbsp;
鏈夊涓嬫暟鎹?(涓轟簡鐪嬪緱鏇存竻妤氾紝鎴戝茍娌℃湁浣跨敤鍥藉浠ｇ爜錛岃屾槸鐩存帴鐢ㄥ浗瀹跺悕浣滀負(fù)Primary Key)
鍥藉錛坈ountry錛?nbsp; 浜哄彛錛坧opulation錛?br /> 涓浗 600
緹庡浗 100
鍔犳嬁澶?nbsp; 100
鑻卞浗 200
娉曞浗 300
鏃ユ湰 250
寰峰浗 200
澧ㄨタ鍝?nbsp; 50
鍗板害 250
鏍規(guī)嵁榪欎釜鍥藉浜哄彛鏁版嵁錛岀粺璁′簹媧插拰鍖楃編媧茬殑浜哄彛鏁伴噺銆傚簲璇ュ緱鍒頒笅闈㈣繖涓粨鏋溿?nbsp;
媧?nbsp; 浜哄彛
浜氭床 1100
鍖楃編媧?nbsp; 250
鍏朵粬 700
鎯寵瑙ｅ喅榪欎釜闂錛屼綘浼?xì)鎬庝箞鍋氾紵鐢熸垚涓涓甫鏈夋床Code鐨刅iew錛屾槸涓涓В鍐蟲柟娉曪紝浣嗘槸榪欐牱寰堥毦鍔ㄦ佺殑鏀瑰彉緇熻鐨勬柟寮忋?nbsp;
濡傛灉浣跨敤Case鍑芥暟錛孲QL浠ｇ爜濡備笅:
SELECT SUM(population),
CASE country
WHEN '涓浗' THEN '浜氭床'
WHEN '鍗板害' THEN '浜氭床'
WHEN '鏃ユ湰' THEN '浜氭床'
WHEN '緹庡浗' THEN '鍖楃編媧?/span>'
WHEN '鍔犳嬁澶?/span>' THEN '鍖楃編媧?/span>'
WHEN '澧ㄨタ鍝?/span>' THEN '鍖楃編媧?/span>'
ELSE '鍏朵粬' END
FROM Table_A
GROUP BY CASE country
WHEN '涓浗' THEN '浜氭床'
WHEN '鍗板害' THEN '浜氭床'
WHEN '鏃ユ湰' THEN '浜氭床'
WHEN '緹庡浗' THEN '鍖楃編媧?/span>'
WHEN '鍔犳嬁澶?/span>' THEN '鍖楃編媧?/span>'
WHEN '澧ㄨタ鍝?/span>' THEN '鍖楃編媧?/span>'
ELSE '鍏朵粬' END;
鍚屾牱鐨勶紝鎴戜滑涔熷彲浠ョ敤榪欎釜鏂規(guī)硶鏉ュ垽鏂伐璧勭殑絳夌駭錛屽茍緇熻姣忎竴絳夌駭鐨勪漢鏁般係QL浠ｇ爜濡備笅錛?nbsp;
SELECT
CASE WHEN salary <= 500 THEN '1'
WHEN salary > 500 AND salary <= 600 THEN '2'
WHEN salary > 600 AND salary <= 800 THEN '3'
WHEN salary > 800 AND salary <= 1000 THEN '4'
ELSE NULL END salary_class,
COUNT(*)
FROM Table_A
GROUP BY
CASE WHEN salary <= 500 THEN '1'
WHEN salary > 500 AND salary <= 600 THEN '2'
WHEN salary > 600 AND salary <= 800 THEN '3'
WHEN salary > 800 AND salary <= 1000 THEN '4'
ELSE NULL END;
浜岋紝鐢ㄤ竴涓猄QL璇彞瀹屾垚涓嶅悓鏉′歡鐨勫垎緇勩?nbsp;
鏈夊涓嬫暟鎹?nbsp;
鍥藉錛坈ountry錛?nbsp; 鎬у埆錛坰ex錛?nbsp; 浜哄彛錛坧opulation錛?br /> 涓浗 1 340
涓浗 2 260
緹庡浗 1 45
緹庡浗 2 55
鍔犳嬁澶?nbsp; 1 51
鍔犳嬁澶?nbsp; 2 49
鑻卞浗 1 40
鑻卞浗 2 60
鎸夌収鍥藉鍜屾у埆榪涜鍒嗙粍錛屽緱鍑虹粨鏋滃涓?nbsp;
鍥藉 鐢?nbsp; 濂?br /> 涓浗 340 260
緹庡浗 45 55
鍔犳嬁澶?nbsp; 51 49
鑻卞浗 40 60
鏅氭儏鍐典笅錛岀敤UNION涔熷彲浠ュ疄鐜扮敤涓鏉¤鍙ヨ繘琛屾煡璇€備絾鏄偅鏍峰鍔犳秷鑰?涓や釜Select閮ㄥ垎)錛岃屼笖SQL璇彞浼?xì)姣旇緝闀裤?br /> 涓嬮潰鏄竴涓槸鐢–ase鍑芥暟鏉ュ畬鎴愯繖涓姛鑳界殑渚嬪瓙
SELECT country,
SUM( CASE WHEN sex = '1' THEN
population ELSE 0 END), --鐢鋒т漢鍙?/span>
SUM( CASE WHEN sex = '2' THEN
population ELSE 0 END) --濂蟲т漢鍙?/span>
FROM Table_A
GROUP BY country;
榪欐牱鎴戜滑浣跨敤Select錛屽畬鎴愬浜岀淮琛ㄧ殑杈撳嚭褰㈠紡錛屽厖鍒嗘樉紺轟簡Case鍑芥暟鐨勫己澶с?nbsp;
涓夛紝鍦–heck涓嬌鐢–ase鍑芥暟銆?nbsp;
鍦–heck涓嬌鐢–ase鍑芥暟鍦ㄥ緢澶氭儏鍐典笅閮芥槸闈炲父涓嶉敊鐨勮В鍐蟲柟娉曘傚彲鑳芥湁寰堝浜烘牴鏈氨涓嶇敤Check錛岄偅涔堟垜寤鴻浣犲湪鐪嬭繃涓嬮潰鐨勪緥瀛愪箣鍚庝篃灝濊瘯涓涓嬪湪SQL涓嬌鐢–heck銆?nbsp;
涓嬮潰鎴戜滑鏉ヤ婦涓緥瀛?nbsp;
鍏徃A錛岃繖涓叕鍙告湁涓瀹氾紝濂寵亴鍛樼殑宸ヨ祫蹇呴』楂樹簬1000鍧椼傚鏋滅敤Check鍜孋ase鏉ヨ〃鐜扮殑璇濓紝濡備笅鎵紺?nbsp;
CONSTRAINT check_salary CHECK
( CASE WHEN sex = '2'
THEN CASE WHEN salary > 1000
THEN 1 ELSE 0 END
ELSE 1 END = 1 )
濡傛灉鍗曠函浣跨敤Check錛屽涓嬫墍紺?nbsp;
CONSTRAINT check_salary CHECK
( sex = '2' AND salary > 1000 )
濂寵亴鍛樼殑鏉′歡鍊掓槸絎﹀悎浜嗭紝鐢瘋亴鍛樺氨鏃犳硶杈撳叆浜嗐?/span>
]]>
set tag=tag+' ', b.articleid=a.articleid, b.classid=a.classid, b.nclassid=a.nclassid
where a.classid=23 and a.nclassid=0 and tagid is not null
update (ctarticle as a left join (ctnclass as c left join ctclass as d on c.classid = d.classid) on a.nclassid = c.nclassid and a.classid = c.classid) left join cttag as b on a.articleid = b.articleid set tag=d.class+' '+c.nclass, b.articleid=a.articleid, b.classid=a.classid, b.nclassid=a.nclassid where a.classid=23 and a.nclassid=197;
鏇存柊鎿嶄綔
宸﹁繛鎺ヤ腑鏁版嵁鐨勭瓫閫?nbsp;
insert into cttag(articleid,classid,nclassid) select a.articleid,a.classid,a.nclassid from ctarticle a left join cttag b on a.articleid=b.articleid where b.articleid is null
//鏈鍙ュ姛鑳戒負(fù), 鏄劇ず涓昏〃鐨勫叏閮ㄥ唴瀹? 鎻掑叆鏁版嵁鍒板壇琛ㄤ腑娌℃湁鐨勬暟鎹?nbsp;
//涓昏浣滅敤涓? 璁╂暟鎹噺灝戝啑浣?nbsp;
涓婁緥涓殑寤剁畫
select a.*, b.*, c.*, d.*
from cttag as d left join ((ctarticle as a left join ctclass as b on a.classid=b.classid) left join ctnclass as c on a.nclassid=c.nclassid) on d.articleid=a.articleid;
鏄劇ず鏂囩珷琛ㄤ腑鐨勫叏閮? 璋冪敤綾誨埆琛ㄤ腑鐨勬爮鐩?nbsp;
select a.*, b.*, c.* from (ctarticle a left join ctclass b on a.classid=b.classid) left join ctnclass c on a.nclassid=c.nclassid
//浣滅敤, 鏈夋椂鍦ㄦ枃绔犺〃涓寘鍚簡鍦ㄤ釜鍒被鍒〃涓病鏈夌殑鏁版嵁, 鐢ㄨ繖涓娉曞彲浠ヨ鍑烘枃绔犺〃鐨勫叏閮ㄦ暟鎹?nbsp;
//a 涓?鏂囩珷琛? b 涓轟富綾誨埆, c 涓哄瓙綾誨埆
鍚屼笂渚? 閫夋嫨榪藉姞鏁版嵁鏃跺姞涓婄┖鏍?nbsp;
insert into cttag(articleid,classid,nclassid,tag)
select a.articleid,a.classid,a.nclassid,d.class+' '+c.nclass
from (ctarticle as a left join (ctnclass c left join ctclass d on c.classid=d.classid) on a.classid=c.classid and a.nclassid=c.nclassid) left join cttag as b on a.articleid = b.articleid where a.classid=4 and a.nclassid=154;
榪炴帴n涓〃, 騫惰拷鍔犳暟鎹埌鍏朵腑涓涓〃, n=4
insert into cttag(articleid,classid,nclassid,tag)
select a.articleid,a.classid,a.nclassid,d.class+c.nclass
from (ctarticle as a left join (ctnclass c left join ctclass d on c.classid=d.classid) on a.classid=c.classid and a.nclassid=c.nclassid) left join cttag as b on a.articleid = b.articleid where a.classid=1 and a.nclassid=1;
//瑙ｈ
鎻掑叆鍒?琛?(鏍?,鏍?,鏍?,鏍?)
閫夋嫨 鍒悕a.鏍?, 鍒悕a.鏍?, 鍒悕a.鏍?, 鍒悕d.鏍? 鍔犱笂 鍒悕c.鏍?
浠?(琛? 鍒悕a 宸﹁繛鎺?(琛? 鍒悕c 宸﹁繛鎺?琛? 鍒悕d 鍦?鍒悕c.鏍? 絳変簬 鍒悕d.鏍?) 鍦?鍒悕a.鏍? 絳変簬 鍒悕c.鏍? 鍜?鍒悕a.鏍?=鍒悕c.鏍?) 宸﹁繛鎺?琛? 鍒悕b 鍦?鍒悕a.鏍? 絳変簬 鍒悕b.鏍? 鍦ㄩ偅閲?鍒悕a.鏍?=1 鍜?鍒悕a.鏍?=1
榪炴帴涓や釜琛? 騫惰拷鍔犳暟鎹埌鍏朵腑涓涓〃
insert into cttag(articleid,classid,nclassid)
select a.articleid,a.classid,a.nclassid
from ctarticle as a left join cttag as b on a.articleid = b.articleid where a.classid=1 and a.nclassid=1;
//瑙ｈ
鎻掑叆鍒?琛?(鏍?,鏍?,鏍?)
閫夋嫨 鍒悕a.鏍?, 鍒悕a.鏍?, 鍒悕a.鏍?
浠?琛? 鍒悕a 宸﹁繛鎺?琛? 鍒悕b 鍦?鍒悕a.鏍? 絳変簬 鍒悕b.鏍? 鍦ㄩ偅閲?鍒悕a.鏍?=1 鍜?鍒悕a.鏍?=1
宸﹁繛鎺?nbsp;
鍚屾涓よ〃鐨勬暟鎹?nbsp;
update ctarticle a inner join cttag b on a.articleid = b.articleid set b.classid=a.classid, b.nclassid=a.nclassid;
//瑙ｈ
鏇存柊 琛? 鍒悕a 鑱旀帴 琛? 鍒悕2 鍦?鍒悕a.鏍? 絳変簬 鍒悕b.鏍? 璁劇疆 鍒悕b.鏍? 鏇存柊涓?鍒悕a.鏍?, 鍒悕b.鏍? 鏇存柊涓?鍒悕a.鏍?
鍙沖榪炴帴
select a.*, b.* from bunclass a right join ctclass b on a.classid=b.classid where a.nclassid=20
鏌ヨ鍒悕 a,b 琛? 鍙尮閰?b 琛ㄤ腑鐨勫唴瀹?
娣誨姞鏁版嵁鍒拌繛鎺ヨ〃涔嬩竴
insert into cttag ( tag, articleid ) select top 1 b.tag, a.articleid from ctarticle as a left join cttag as b on a.articleid = b.articleid where a.articleid order by a.articleid desc;
鍙橀氫腑鐨勭敤娉曚簩
insert into bureply
select b.*, a.classid, a.nclassid
from article as a inner join reply as b on a.articleid = b.articleid
where classid=50;
瀹為檯搴旂敤涓殑鍙橀?nbsp;
insert into butag ( tag, articleid, classid, nclassid)
select b.tag, a.articleid, a.classid, a.nclassid
from article as a inner join tag as b on a.articleid = b.articleid
where classid=24;
娣誨姞鏁版嵁鍒板叾浠栬〃
insert into butag ( tag, articleid )
select b.tag, a.articleid
from article as a inner join tag as b on a.articleid = b.articleid
where a.articleid<>false;
//瑙ｈ
娣誨姞鍒?鎺ユ敹琛?鍒?,鍒?)
閫夋嫨 鍒悕b.鍒?, 鍒悕a.鍒?
浠?琛? 琛ㄥ悕a 鑱旀帴 琛? 琛ㄥ悕b 鍦?鍒悕a.鍒梒 絳変簬 鍒悕b.鍒梒
鍦ㄥ摢閲?鍒悕a.鍒梒 涓嶇瓑浜?娌℃湁
瀹為檯搴旂敤涓殑鍙橀?nbsp;
select b.tag, a.articleid, a.classid, a.nclassid
from article as a inner join tag as b on a.articleid = b.articleid
where a.classid=24;
鏌ヨ
select b.tag, a.articleid
from article as a inner join tag as b on a.articleid = b.articleid
where a.articleid<>false;
//瑙ｈ
閫夋嫨 鍒悕b.鍒? 鍒悕a.鍒?nbsp;
浠?琛? 鍒悕a 鑱旀帴 琛? 鍒悕b 鍦?鍒悕a.鍒梒 = 鍒悕b.鍒梒
鍦ㄥ摢閲?鍒悕a.鍒梒 涓嶇瓑浜?娌℃湁
娉? as 涓嶆槸蹇呰
]]>
IN:紜畾緇欏畾鐨勫兼槸鍚︿笌瀛愭煡璇㈡垨鍒楄〃涓殑鍊肩浉鍖歸厤銆?br /> IN 鍏抽敭瀛椾嬌鎮(zhèn)ㄥ緱浠ラ夋嫨涓庡垪琛ㄤ腑鐨勪換鎰忎竴涓煎尮閰嶇殑琛屻?br /> 褰撹鑾峰緱灞呬綇鍦?California銆両ndiana 鎴?Maryland 宸炵殑鎵鏈変綔鑰呯殑濮撳悕鍜屽窞鐨勫垪琛ㄦ椂錛屽氨闇瑕佷笅鍒楁煡璇細(xì)
SELECT ProductID, ProductName FROM Northwind.dbo.Products WHERE CategoryID = 1 OR CategoryID = 4 OR CategoryID = 5
鐒惰岋紝濡傛灉浣跨敤 IN錛屽皯閿叆涓浜涘瓧絎︿篃鍙互寰楀埌鍚屾牱鐨勭粨鏋滐細(xì)
SELECT ProductID, ProductName FROM Northwind.dbo.Products WHERE CategoryID IN (1, 4, 5)
IN 鍏抽敭瀛椾箣鍚庣殑欏圭洰蹇呴』鐢ㄩ楀彿闅斿紑錛屽茍涓旀嫭鍦ㄦ嫭鍙蜂腑銆?br /> 涓嬪垪鏌ヨ鍦?titleauthor 琛ㄤ腑鏌ユ壘鍦ㄤ換涓縐嶄功涓緱鍒扮殑鐗堢◣灝戜簬 50% 鐨勬墍鏈変綔鑰呯殑 au_id錛岀劧鍚庝粠 authors 琛ㄤ腑閫夋嫨 au_id 涓?br /> titleauthor 鏌ヨ緇撴灉鍖歸厤鐨勬墍鏈変綔鑰呯殑濮撳悕錛?nbsp;
SELECT au_lname, au_fname FROM authors WHERE au_id IN (SELECT au_id FROM titleauthor WHERE royaltyper < 50)
緇撴灉鏄劇ず鏈変竴浜涗綔鑰呭睘浜庡皯浜?50% 鐨勪竴綾匯?br /> NOT IN:閫氳繃 NOT IN 鍏抽敭瀛楀紩鍏ョ殑瀛愭煡璇篃榪斿洖涓鍒楅浂鍊兼垨鏇村鍊箋?br /> 浠ヤ笅鏌ヨ鏌ユ壘娌℃湁鍑虹増榪囧晢涓氫功綾嶇殑鍑虹増鍟嗙殑鍚嶇О銆?br /> SELECT pub_name FROM publishers WHERE pub_id NOT IN (SELECT pub_id FROM titles WHERE type = 'business')
浣跨敤 EXISTS 鍜?NOT EXISTS 寮曞叆鐨勫瓙鏌ヨ鍙敤浜庝袱縐嶉泦鍚堝師鐞嗙殑鎿嶄綔錛氫氦闆嗕笌宸泦銆備袱涓泦鍚堢殑浜ら泦鍖呭惈鍚屾椂灞炰簬涓や釜鍘熼泦鍚堢殑鎵鏈夊厓绱犮?br /> 宸泦鍖呭惈鍙睘浜庝袱涓泦鍚堜腑鐨勭涓涓泦鍚堢殑鍏冪礌銆?br /> EXISTS:鎸囧畾涓涓瓙鏌ヨ錛屾嫻嬭鐨勫瓨鍦ㄣ?nbsp;
鏈ず渚嬫墍紺烘煡璇㈡煡鎵劇敱浣嶄簬浠ュ瓧姣?B 寮澶寸殑鍩庡競涓殑浠諱竴鍑虹増鍟嗗嚭鐗堢殑涔﹀悕錛?br /> SELECT DISTINCT pub_name FROM publishers WHERE EXISTS (SELECT * FROM titles WHERE pub_id = publishers.pub_id AND type =
'business')
SELECT distinct pub_name FROM publishers WHERE pub_id IN (SELECT pub_id FROM titles WHERE type = 'business')
涓よ呯殑鍖哄埆:
EXISTS:鍚庨潰鍙互鏄暣鍙ョ殑鏌ヨ璇彞濡?SELECT * FROM titles
IN:鍚庨潰鍙兘鏄鍗曞垪:SELECT pub_id FROM titles
NOT EXISTS:
渚嬪錛岃鏌ユ壘涓嶅嚭鐗堝晢涓氫功綾嶇殑鍑虹増鍟嗙殑鍚嶇О錛?br /> SELECT pub_name FROM publishers WHERE NOT EXISTS (SELECT * FROM titles WHERE pub_id = publishers.pub_id AND type =
'business')
涓嬮潰鐨勬煡璇㈡煡鎵懼凡緇忎笉閿鍞殑涔︾殑鍚嶇О:
SELECT title FROM titles WHERE NOT EXISTS (SELECT title_id FROM sales WHERE title_id = titles.title_id)
]]>
鍦ㄦ暟鎹簱琛ㄤ腑浼?xì)鏈墭q欐牱鐨勪竴涓瓧孌電敤鏉ュ尯鍒褰曠殑灞炴э紝濡傦細(xì)鍦ㄥ鎴瘋〃涓湁涓涓瓧孌佃〃紺哄鎴風(fēng)駭鍒紝褰撹繖涓褰曚負(fù)A鏃舵槸涓綰у鎴鳳紝涓?span lang="EN-US">B鏃舵槸浜岀駭瀹㈡埛銆傚湪鐢?span lang="EN-US">hiberante鍋?span lang="EN-US">OR琛ㄧず鏃剁被鍙兘鏄繖鏍風(fēng)殑錛?/span>
public class Customer{
private String flag; //琛ㄧず瀹㈡埛鐨勭駭鍒?/span>
...
}
鐒跺悗錛屽湪紼嬪簭涓墜鍔ㄦ帶鍒?span lang="EN-US">flag鐨勫鹼紝浣嗘槸榪欐牱褰撴瘡涓駭鐨勫鎴鋒湁涓嶅悓鐨勫睘鎬ф椂Customer綾誨皢鍖呭惈鎵鏈夌駭鍒殑灞炴э紝榪欐牱涓嶆槸寰堝ソ銆?/span>
hibernate鎻愪緵涓涓?span lang="EN-US">Discriminator鏄犲皠鐨勬柟娉曪紝灝辨槸鎶婁竴涓〃鏄犲皠鎴愪笉鍚岀殑綾伙紝鏈変笉鍚岀殑灞炴с?/span>
public class Customer{
//鍖呭惈鎵鏈夌駭鍒殑鍏叡灞炴?/span>
...
}
public class CustomerA extends Customer{
//鍙寘鎷竴綰у鎴風(fēng)殑鐗規(guī)湁灞炴?/span>
}
public class CustomerB extends Customer{
//鍙寘鍚簩綰у鎴風(fēng)壒鏈夌殑灞炴?/span>
}
榪欐牱鏇寸鍚堥潰鍚戝璞＄殑鍘熷垯錛岀劧鍚庡湪hbm.xml涓繖鏍峰啓錛?/span>
<id name="id" type="int">
...
</id>
<discriminator column="flag" type="string" />
<!-- 鍏叡灞炴х殑鏄犲皠 -->
<subclass name="CustomerA" discriminator-value="A">
<!-- 涓綰у鎴風(fēng)壒鏈夊睘鎬х殑鏄犲皠 -->
</subclass>
<subclass name="CustomerB" discriminator-value="B">
<!-- 浜岀駭瀹㈡埛鐗規(guī)湁灞炴х殑鏄犲皠 -->
</subclass>
榪欐牱灝卞彲浠ュ崟鐙殑鐢?span lang="EN-US">CustomerA,CustomerB榪欐牱鐨勫疄渚嬩簡錛屽仛鏁版嵁搴撲慨鏀規(guī)椂灝變笉鐢ㄥ叧蹇?span lang="EN-US">flag瀛楁鐨勫間簡錛屼細(xì)鑷姩鐨勫姞A鎴?span lang="EN-US">B銆?/span>
濡傛灉鏄嬌鐢?span lang="EN-US">hibernate Annotation鑰屼笉鏄?span lang="EN-US">xml鏉ユ弿榪版槧璋㈠叧緋伙紝浠ｇ爜濡備笅錛?/span>
@Entity
@Table(name = "customer")
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name = "flag", discriminatorType = DiscriminatorType.STRING)
public class Customer{
}
@Entity
@DiscriminatorValue(value = "A")
public class CustomerA extends Customer{
}
@Entity
@DiscriminatorValue(value = "B")
public class CustomerB extends Customer{
}
榪欐牱灝卞彲浠ヤ簡銆?/span>
]]>