注释
å½?SET XACT_ABORT ä¸?ON æ—Óž¼Œå¦‚æžœ Transact-SQL è¯å¥äº§ç”Ÿ˜q行旉™”™è¯¯ï¼Œæ•´ä¸ªäº‹åŠ¡ž®†ç»ˆæ¢åƈ回滚。äØ“ OFF æ—Óž¼Œåªå›žæ»šäñ”生错误的 Transact-SQL è¯å¥åQŒè€Œäº‹åŠ¡å°†¾l§ç®‹˜q›è¡Œå¤„ç†ã€‚编译错误（如è¯æ³•é”™è¯¯ï¼‰ä¸å— SET XACT_ABORT 的媄å“ã€?br />
SET QUOTED_IDENTIFIER{ ON | OFF }
注释
å½?SET QUOTED_IDENTIFIER ä¸?ON æ—Óž¼Œæ ‡è¯†½W¦å¯ä»¥ç”±åŒå¼•å·åˆ†éš”，而文å—å¿…™åÈ”±å•å¼•å·åˆ†éš”。当 SET QUOTED_IDENTIFIER ä¸?OFF æ—Óž¼Œæ ‡è¯†½W¦ä¸å¯åŠ 引å·åQŒä¸”å¿…é¡»½W¦åˆæ‰€æœ?Transact-SQL æ ‡è¯†½W¦è§„则ã€?/p>
SET ANSI_NULLS { ON | OFF }
注释
SQL-92 æ ‡å‡†è¦æ±‚在对½Iºå€ÆD¿›è¡Œç‰äº?(=) 或丽{‰äºŽ (<>) 比较时å–å€égØ“ FALSE。当 SET ANSI_NULLS ä¸?ON æ—Óž¼Œå³ä‹É column_name ä¸åŒ…å«ç©ºå€û|¼Œä½¿ç”¨ WHERE column_name = NULL çš?SELECT è¯å¥ä»è¿”回零行。å³ä½?column_name ä¸åŒ…å«éž½Iºå€û|¼Œä½¿ç”¨ WHERE column_name <> NULL çš?SELECT è¯å¥ä»ä¼š˜q”回零行ã€?
å½?SET ANSI_NULLS ä¸?OFF æ—Óž¼Œ½{‰äºŽ (=) 和丽{‰äºŽ (<>) 比较˜qç®—½W¦ä¸éµä»Ž SQL-92 æ ‡å‡†ã€‚ä‹Éç”?WHERE column_name = NULL çš?SELECT è¯å¥˜q”回 column_name ä¸åŒ…å«ç©ºå€¼çš„行。ä‹Éç”?WHERE column_name <> NULL çš?SELECT è¯å¥˜q”回列ä¸åŒ…å«éžç©ºå€¼çš„行。æ¤å¤–，使用 WHERE column_name <> XYZ_value çš?SELECT è¯å¥˜q”回所有ä¸ä¸?XYZ_value 也ä¸ä¸?NULL çš„è¡Œã€?
select id, name, coden
from cims_supplier
where name like 'A%'
and coden like 'A%'
union
select cdbregno as id,
dbms_lob.substr(supplier_name,2000,1) as name,
coden as coden
from acdsupplier_moltable
where supplier_name like 'A%'
and coden like 'A%'
cims_supplier表ä¸çš„name是varchar2¾cÕdž‹, 而acdsupplier_moltable表ä¸çš„supplier_name为clob¾cÕdž‹, ˜q™æ ·ž®±å¯ä»¥unionäº?
当然排åºä¹Ÿå¯ä»¥äº†.
select * from t1 order by dbms_lob.substr(clobcloum,2000,1);
有时候需è¦æ‰¹é‡åŒæ¥æ•°æ®åº“çš„default value ¾U¦æŸ(constraint)åQŒåœ¨SQL2005ä¸ï¼Œå¯ä»¥é€šè¿‡sys.default_constraints¾pÈ»Ÿè§†å›¾æ¥èŽ·å–该数æ®åº“的视图或者æŸä¸ªè¡¨å¯¹åº”的视图ã€?
该视å›ùN»˜è®¤å¯¹åº”å—ŒD?
nameåQšçº¦æŸå
object_id åQšçº¦æŸID
parent_object_idåQšçº¦æŸå¯¹åº”的表ID
parent_column_idåQšçº¦æŸå¯¹åº”表ä¸çš„½W¬å‡ åˆ?
definitionåQšé»˜è®¤å€?
如下SQL查询defaulttestæ•°æ®åº“ä¸test1表所有的default value constraints ã€?
SELECT * FROM sys.default_constraints WHERE sys.default_constraints.parent_object_id=OBJECT_ID('test1')
修改带有¾U¦æŸçš„æ•°æ®è¡¨¾l“æž„è®²äº†å¦‚ä½•åˆ é™¤å’Œæ·»åŠ çº¦æŸï¼Œä¸‹é¢çš„è¯å¥ä¼šåˆ—出所有的default value constraintã€?
SELECT
sys.default_constraints.name AS name,
sys.[tables].name AS tablename
FROM sys.default_constraints
LEFT JOIN sys.tables ON
sys.[tables].object_id=sys.[default_constraints].parent_object_id
然åŽä½¿ç”¨æ¸¸æ ‡éåŽ†åˆ é™¤å¯¹åº”è¡¨çš„¾U¦æŸå›_¯
例，有如下更新æ¡ä»?
- 工资5000以上的èŒå‘˜ï¼Œå·¥èµ„å‡å°‘10%
- 工资åœ?000åˆ?600之间的èŒå‘˜ï¼Œå·¥èµ„å¢žåŠ 15%
--æ¡äšg1 UPDATE Personnel SET salary = salary * 0.9 WHERE salary >= 5000; --æ¡äšg2 UPDATE Personnel SET salary = salary * 1.15 WHERE salary >= 2000 AND salary < 4600;
但是事情没有惌™±¡å¾—那么简å•ï¼Œå‡è®¾æœ‰ä¸ªäººå·¥èµ?000å—。首先，按照æ¡äšg1åQŒå·¥èµ„凞®?0%åQŒå˜æˆå·¥èµ?500。接下楘qè¡Œ½W¬äºŒä¸ªSQLæ—¶å€™ï¼Œå› äØ“˜q™ä¸ªäººçš„工资æ˜?500åœ?000åˆ?600的范围之内， éœ€å¢žåŠ 15%åQŒæœ€åŽè¿™ä¸ªäh的工资结果是5175,ä¸ä½†æ²¡æœ‰å‡å°‘åQŒåè€Œå¢žåŠ äº†ã€‚å¦‚æžœè¦æ˜¯å˜q‡æ¥æ‰§è¡ŒåQŒé‚£ä¹ˆå·¥èµ?600çš„äh相å会å˜æˆå‡ž®‘工资。暂且丽Ž¡è¿™ä¸ªè§„ç« æ˜¯å¤šä¹ˆè’诞åQŒå¦‚果想è¦ä¸€ä¸ªSQL è¯å¥å®žçŽ°˜q™ä¸ªåŠŸèƒ½çš„è¯åQŒæˆ‘们需è¦ç”¨åˆ°Case函数。代ç 如ä¸?
UPDATE Personnel SET salary = CASE WHEN salary >= 5000 　 THEN salary * 0.9 WHEN salary >= 2000 AND salary < 4600 THEN salary * 1.15 ELSE salary END;
˜q™é‡Œè¦æ³¨æ„一点，最åŽä¸€è¡Œçš„ELSE salary是必需的，è¦æ˜¯æ²¡æœ‰˜q™è¡ŒåQŒä¸½W¦åˆ˜q™ä¸¤ä¸ªæ¡ä»¶çš„人的工资ž®†ä¼šè¢«å†™æˆNUll,那寞®±å¤§äº‹ä¸å¦™äº†ã€‚在Case函数ä¸Else部分的默认值是NULLåQŒè¿™ç‚ÒŽ˜¯éœ€è¦æ³¨æ„的地方ã€?
˜q™ç§æ–ÒŽ³•˜q˜å¯ä»¥åœ¨å¾ˆå¤šåœ°æ–¹ä½¿ç”¨åQŒæ¯”如说å˜æ›´ä¸»é”®˜q™ç§ç´¯æ´»ã€?
一般情况下åQŒè¦æƒÏxŠŠä¸¤æ¡æ•°æ®çš„Primary key,aå’Œb交æ¢åQŒéœ€è¦ç»˜q‡äÍæ—¶å˜å‚¨ï¼Œæ‹¯‚´åQŒè¯»å›žæ•°æ®çš„三个˜q‡ç¨‹åQŒè¦æ˜¯ä‹É用Case函数的è¯åQŒä¸€åˆ‡éƒ½å˜å¾—½Ž€å•å¤šäº†ã€?
| p_key | col_1 | col_2 |
| a | 1 | å¼ ä¸‰ |
| b | 2 | æŽå›› |
| c | 3 | 王五 |
å‡è®¾æœ‰å¦‚上数æ®ï¼Œéœ€è¦æŠŠä¸»é”®
aå’?code>bç›æ€º’交æ¢ã€‚用Case函数æ¥å®žçŽ°çš„è¯ï¼Œä»£ç 如下 UPDATE SomeTable SET p_key = CASE WHEN p_key = 'a' THEN 'b' WHEN p_key = 'b' THEN 'a' ELSE p_key END WHERE p_key IN ('a', 'b');
åŒæ ·çš„也å¯ä»¥äº¤æ¢ä¸¤ä¸ªUnique key。需è¦æ³¨æ„的是，如果有需è¦äº¤æ¢ä¸»é”®çš„情况å‘生åQŒå¤šåŠæ˜¯å½“åˆå¯¹è¿™ä¸ªè¡¨çš„设计进行得ä¸å¤ŸåˆîC½åQŒå¾è®®æ£€æŸ¥è¡¨çš„设计是å¦å¦¥å½“ã€?
五，两个表数æ®æ˜¯å¦ä¸€è‡´çš„‹‚€æŸ¥ã€?/strong>
Case函数ä¸åŒäºŽDECODE函数。在Case函数ä¸ï¼Œå¯ä»¥ä½¿ç”¨BETWEEN,LIKE,IS NULL,IN,EXISTS½{‰ç‰ã€‚比如说使用IN,EXISTSåQŒå¯ä»¥è¿›è¡Œå查询åQŒä»Žè€?实现更多的功能ã€?
下é¢å…·ä¸ªä¾‹åæ¥è¯´æ˜Žï¼Œæœ‰ä¸¤ä¸ªè¡¨åQŒtbl_A,tbl_BåQŒä¸¤ä¸ªè¡¨ä¸éƒ½æœ‰keyCol列。现在我们对两个表进行比较，tbl_Aä¸çš„keyCol列的数æ®å¦‚果在tbl_Bçš„keyCol列的数æ®ä¸å¯ä»¥æ‰¾åˆŽÍ¼Œ ˜q”回¾l“æžœ'Matched',如果没有扑ֈ°åQŒè¿”回结æž?Unmatched'ã€?
è¦å®žçŽîC¸‹é¢è¿™ä¸ªåŠŸèƒ½ï¼Œå¯ä»¥ä½¿ç”¨ä¸‹é¢ä¸¤æ¡è¯å¥
--使用IN的时�/span>
SELECT keyCol,
CASE WHEN keyCol IN ( SELECT keyCol FROM tbl_B )
THEN 'Matched'
ELSE 'Unmatched' END Label
FROM tbl_A;
--使用EXISTS的时�/span>
SELECT keyCol,
CASE WHEN EXISTS ( SELECT * FROM tbl_B
WHERE tbl_A.keyCol = tbl_B.keyCol )
THEN 'Matched'
ELSE 'Unmatched' END Label
FROM tbl_A;
使用INå’ŒEXISTS的结果是相åŒçš„。也å¯ä»¥ä½¿ç”¨NOT INå’ŒNOT EXISTSåQŒä½†æ˜¯è¿™ä¸ªæ—¶å€™è¦æ³¨æ„NULL的情å†üc€?
å…，在Case函数ä¸ä‹É用åˆè®¡å‡½æ•?/strong>
å‡è®¾æœ‰ä¸‹é¢ä¸€ä¸ªè¡¨
| å¦å·(std_id) | 评¡¨‹ID(class_id) | 评¡¨‹å?class_name) | ä¸ÖM¿®flagåQˆmain_class_flg) |
| 100 | 1 | ¾l济å?/td> | Y |
| 100 | 2 | 历å²å?/td> | N |
| 200 | 2 | 历å²å?/td> | N |
| 200 | 3 | 考å¤å?/td> | Y |
| 200 | 4 | 计算�/td> | N |
| 300 | 4 | 计算�/td> | N |
| 400 | 5 | åŒ–å¦ | N |
| 500 | 6 | æ•°å¦ | N |
有的å¦ç”Ÿé€‰æ‹©äº†åŒæ—¶ä¿®å‡ 门评¡¨‹(100,200)也有的å¦ç”Ÿåªé€‰æ‹©äº†ä¸€é—¨è¯¾½E?300,400,500)。选修多门评¡¨‹çš„å¦ç”Ÿï¼Œè¦é€‰æ‹©ä¸€é—¨è¯¾½E‹ä½œä¸ÞZ¸»ä¿®ï¼Œä¸ÖM¿®flag里é¢å†™å…¥ Y。åªé€‰æ‹©ä¸€é—¨è¯¾½E‹çš„å¦ç”ŸåQŒä¸»ä¿®flag为N(实际上è¦æ˜¯å†™å…¥Yçš„è¯åQŒå°±æ²¡æœ‰ä¸‹é¢çš„麻烦事了，ä¸ÞZº†ä¸¾ä¾‹å，˜q˜è¯·å¤šå¤šåŒ…å«)ã€?
现在我们è¦æŒ‰ç…§ä¸‹é¢ä¸¤ä¸ªæ¡ä»¶å¯¹˜q™ä¸ªè¡¨è¿›è¡ŒæŸ¥è¯?
- åªé€‰ä¿®ä¸€é—¨è¯¾½E‹çš„人，˜q”回那门评¡¨‹çš„ID
- 选修多门评¡¨‹çš„ähåQŒè¿”回所选的主课½E‹ID
½Ž€å•çš„æƒÏx³•ž®±æ˜¯åQŒæ‰§è¡Œä¸¤æ¡ä¸åŒçš„SQLè¯å¥˜q›è¡ŒæŸ¥è¯¢ã€?
æ¡äšg1
--æ¡äšg1åQšåªé€‰æ‹©äº†ä¸€é—¨è¯¾½E‹çš„å¦ç”Ÿ SELECT std_id, MAX(class_id) AS main_class FROM Studentclass GROUP BY std_id HAVING COUNT(*) = 1;
执行¾l“æžœ1
STD_ID MAIN_class
------ ----------
300 4
400 5
500 6
æ¡äšg2
--æ¡äšg2åQšé€‰æ‹©å¤šé—¨è¯„¡¨‹çš„å¦ç”?/span>
SELECT std_id, class_id AS main_class
FROM Studentclass
WHERE main_class_flg = 'Y' ;
执行¾l“æžœ2
STD_ID MAIN_class
------ ----------
100 1
200 3
如果使用Case函数åQŒæˆ‘们åªè¦ä¸€æ¡SQLè¯å¥ž®±å¯ä»¥è§£å†³é—®é¢˜ï¼Œå…·ä½“如下所½C?
SELECT std_id, CASE WHEN COUNT(*) = 1 --åªé€‰æ‹©ä¸€é—¨è¯¾½E‹çš„å¦ç”Ÿçš„情å†?/span> THEN MAX(class_id) ELSE MAX(CASE WHEN main_class_flg = 'Y' THEN class_id ELSE NULL END ) END AS main_class FROM Studentclass GROUP BY std_id;
˜qè¡Œ¾l“æžœ
STD_ID MAIN_class
------ ----------
100 1
200 3
300 4
400 5
500 6
通过在Case函数ä¸åµŒå¥—Case函数åQŒåœ¨åˆè®¡å‡½æ•°ä¸ä‹É用Case函数½{‰æ–¹æ³•ï¼Œæˆ‘们å¯ä»¥è½ÀL¾çš„解册™¿™ä¸ªé—®é¢˜ã€‚ä‹É用Case函数¾l™æˆ‘们带æ¥äº†æ›´å¤§çš„自由度ã€?
最åŽæ醒一下ä‹É用Case函数的新手注æ„ä¸è¦çŠ¯ä¸‹é¢çš„é”™è¯?
CASE col_1 WHEN 1 　 THEN 'Right' WHEN NULL THEN 'Wrong' END
在这个è¯å¥ä¸When Null˜q™ä¸€è¡Œæ€ÀL˜¯˜q”回unknownåQŒæ‰€ä»¥æ°¸˜qœä¸ä¼šå‡ºçŽ°Wrong的情å†üc€‚å› ä¸ø™¿™å¥å¯ä»¥æ›¿æ¢æˆWHEN col_1 = NULLåQŒè¿™æ˜¯ä¸€ä¸ªé”™è¯¯çš„用法åQŒè¿™ä¸ªæ—¶å€™æˆ‘们应该选择用WHEN col_1 IS NULLã€?img src ="http://www.aygfsteel.com/rain1102/aggbug/230840.html" width = "1" height = "1" />
--½Ž€å•Case函数 CASE sex WHEN '1' THEN 'ç”? WHEN '2' THEN 'å¥? ELSE '其他' END --Caseæœçƒ¦å‡½æ•° CASE WHEN sex = '1' THEN 'ç”? WHEN sex = '2' THEN 'å¥? ELSE '其他' END
˜q™ä¸¤¿Uæ–¹å¼ï¼Œå¯ä»¥å®žçŽ°ç›¸åŒçš„功能。简å•Case函数的写法相å¯ÒŽ¯”较简‹z，但是和Caseæœçƒ¦å‡½æ•°ç›¸æ¯”åQŒåŠŸèƒ½æ–¹é¢ä¼šæœ‰äº›é™åˆ¶åQŒæ¯”如写判æ–å¼ã€?
˜q˜æœ‰ä¸€ä¸ªéœ€è¦æ³¨æ„的问题åQŒCase函数åªè¿”回第一个符åˆæ¡ä»¶çš„å€û|¼Œå‰©ä¸‹çš„Case部分ž®†ä¼šè¢«è‡ªåŠ¨å¿½ç•¥ã€?
--比如è¯ß_¼Œä¸‹é¢˜q™æ®µSQLåQŒä½ æ°¸è¿œæ— æ³•å¾—åˆ°“½W¬äºŒ¾c?#8221;˜q™ä¸ª¾l“æžœ CASE WHEN col_1 IN ( 'a', 'b') THEN '½W¬ä¸€¾c? WHEN col_1 IN ('a') THEN '½W¬äºŒ¾c? ELSE'其他' END
下é¢æˆ‘们æ¥çœ‹ä¸€ä¸‹ï¼Œä½¿ç”¨Case函数都能åšäº›ä»€ä¹ˆäº‹æƒ…ã€?
一åQŒå·²çŸ¥æ•°æ®æŒ‰ç…§å¦å¤–一¿Uæ–¹å¼è¿›è¡Œåˆ†¾l„，分æžã€?/strong>
有如下数æ?(ä¸ÞZº†çœ‹å¾—更清楚，我åƈ没有使用国家代ç åQŒè€Œæ˜¯ç›´æŽ¥ç”¨å›½å®¶å作äØ“Primary Key)
| 国家åQˆcountryåQ?/td> | 人å£åQˆpopulationåQ?/td> |
| ä¸å›½ | 600 |
| ¾ŸŽå›½ | 100 |
| åŠ æ‹¿å¤?/td> | 100 |
| 英国 | 200 |
| 法国 | 300 |
| 日本 | 250 |
| 德国 | 200 |
| 墨西�/td> | 50 |
| å°åº¦ | 250 |
æ ÒŽ®˜q™ä¸ªå›½å®¶äººå£æ•°æ®åQŒç»Ÿè®¡äºš‹z²å’ŒåŒ—美‹z²çš„人å£æ•°é‡ã€‚应该得åˆîC¸‹é¢è¿™ä¸ªç»“æžœã€?
| ‹z?/td> | äººå£ |
| 亚洲 | 1100 |
| 北美‹z?/td> | 250 |
| 其他 | 700 |
惌™¦è§£å†³˜q™ä¸ªé—®é¢˜åQŒä½ 会怎么åšï¼Ÿç”Ÿæˆä¸€ä¸ªå¸¦æœ‰æ´²Codeçš„ViewåQŒæ˜¯ä¸€ä¸ªè§£å†Ïx–¹æ³•ï¼Œä½†æ˜¯˜q™æ ·å¾ˆéš¾åŠ¨æ€çš„改嘾lŸè®¡çš„æ–¹å¼ã€?
如果使用Case函数åQŒSQL代ç 如下:
SELECT SUM(population), CASE country WHEN 'ä¸å›½' THEN '亚洲' WHEN 'å°åº¦' THEN '亚洲' WHEN '日本' THEN '亚洲' WHEN '¾ŸŽå›½' THEN '北美‹z? WHEN 'åŠ æ‹¿å¤? THEN '北美‹z? WHEN '墨西å“? THEN '北美‹z? ELSE '其他' END FROM Table_A GROUP BY CASE country WHEN 'ä¸å›½' THEN '亚洲' WHEN 'å°åº¦' THEN '亚洲' WHEN '日本' THEN '亚洲' WHEN '¾ŸŽå›½' THEN '北美‹z? WHEN 'åŠ æ‹¿å¤? THEN '北美‹z? WHEN '墨西å“? THEN '北美‹z? ELSE '其他' END;
åŒæ ·çš„，我们也å¯ä»¥ç”¨˜q™ä¸ªæ–ÒŽ³•æ¥åˆ¤æ–工资的½{‰çñ”åQŒåƈ¾lŸè®¡æ¯ä¸€½{‰çñ”çš„äh数。SQL代ç 如下åQ?
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;
二，用一个SQLè¯å¥å®Œæˆä¸åŒæ¡äšg的分¾l„ã€?/strong>
有如下数æ?
| 国家åQˆcountryåQ?/td> | 性别åQˆsexåQ?/td> | 人å£åQˆpopulationåQ?/td> |
| ä¸å›½ | 1 | 340 |
| ä¸å›½ | 2 | 260 |
| ¾ŸŽå›½ | 1 | 45 |
| ¾ŸŽå›½ | 2 | 55 |
| åŠ æ‹¿å¤?/td> | 1 | 51 |
| åŠ æ‹¿å¤?/td> | 2 | 49 |
| 英国 | 1 | 40 |
| 英国 | 2 | 60 |
按照国家和性别˜q›è¡Œåˆ†ç»„åQŒå¾—出结果如ä¸?
| 国家 | �/td> | �/td> |
| ä¸å›½ | 340 | 260 |
| ¾ŸŽå›½ | 45 | 55 |
| åŠ æ‹¿å¤?/td> | 51 | 49 |
| 英国 | 40 | 60 |
普通情况下åQŒç”¨UNION也å¯ä»¥å®žçŽ°ç”¨ä¸€æ¡è¯å¥è¿›è¡ŒæŸ¥è¯¢ã€‚ä½†æ˜¯é‚£æ ·å¢žåŠ æ¶ˆè€?两个Select部分)åQŒè€Œä¸”SQLè¯å¥ä¼šæ¯”较长ã€?
下é¢æ˜¯ä¸€ä¸ªæ˜¯ç”¨Case函数æ¥å®Œæˆè¿™ä¸ªåŠŸèƒ½çš„例å
SELECT country, SUM( CASE WHEN sex = '1' THEN population ELSE 0 END), --ç”äh€§ähå?/span> SUM( CASE WHEN sex = '2' THEN population ELSE 0 END) --å¥Ïx€§ähå?/span> FROM Table_A GROUP BY country;
˜q™æ ·æˆ‘们使用SelectåQŒå®Œæˆå¯¹äºŒç»´è¡¨çš„输出形å¼åQŒå……分显½CÞZº†Case函数的强大ã€?
三，在Checkä¸ä‹É用Case函数ã€?/strong>
在Checkä¸ä‹É用Case函数在很多情况下都是éžå¸¸ä¸é”™çš„解å†Ïx–¹æ³•ã€‚å¯èƒ½æœ‰å¾ˆå¤šäººæ ¹æœ¬å°±ä¸ç”¨CheckåQŒé‚£ä¹ˆæˆ‘å»ø™®®ä½ 在看过下é¢çš„例å之åŽä¹Ÿž®è¯•ä¸€ä¸‹åœ¨SQLä¸ä‹É用Checkã€?
下é¢æˆ‘们æ¥ä‹D个例å?
å…¬å¸AåQŒè¿™ä¸ªå…¬å¸æœ‰ä¸ªè§„定，奌™Œå‘˜çš„工资必须高于1000å—。如果用Checkå’ŒCaseæ¥è¡¨çŽ°çš„è¯ï¼Œå¦‚下所½C?
CONSTRAINT check_salary CHECK ( CASE WHEN sex = '2' THEN CASE WHEN salary > 1000 THEN 1 ELSE 0 END ELSE 1 END = 1 )
如果å•çº¯ä½¿ç”¨CheckåQŒå¦‚下所½C?
CONSTRAINT check_salary CHECK ( sex = '2' AND salary > 1000 )
奌™Œå‘˜çš„æ¡äšg倒是½W¦åˆäº†ï¼Œç”¯‚Œå‘˜å°±æ— 法输入了ã€?
USE pubs GO SELECT CASE WHEN price IS NULL THEN 'Unpriced' WHEN price < 10 THEN 'Bargain' WHEN price BETWEEN 10 and 20 THEN 'Average' ELSE 'Gift to impress relatives' END AS Range, Title FROM titles GROUP BY CASE WHEN price IS NULL THEN 'Unpriced' WHEN price < 10 THEN 'Bargain' WHEN price BETWEEN 10 and 20 THEN 'Average' ELSE 'Gift to impress relatives' END, Title ORDER BY CASE WHEN price IS NULL THEN 'Unpriced' WHEN price < 10 THEN 'Bargain' WHEN price BETWEEN 10 and 20 THEN 'Average' ELSE 'Gift to impress relatives' END, Title GO
从表ä¸åˆ 除é‡å¤è®°å½?
解决æ–ÒŽ¡ˆ
用带有èšé›†å‡½æ•°çš„å查è¯? 例如MIN, ä»ÀL„选择ä¿ç•™çš„ID(本例ä¸åªä¿ç•™æ¯ç»„ä¸IDåähœ€ž®çš„记录):
delete from dept
where id not in (select min(id)
from dept
group by name)
meetings = mgr.createQuery("select new com.integral7.ejb3.investigations.Meeting(m.id, m.scheduledDate, m.type.name, m.description, " +
"case when exists(select id from MeetingAudit ma where ma.meeting = m and ma.audit.id = ?0) then True else False end) " +
" from Meeting m " +
" where m.owner.id = ?1 and m.scheduledDate >= ?2 order by m.scheduledDate asc")
.setParameter(0, candidateId)
.setParameter(1, ownerId)
.setParameter(2, DateUtils.convertToBeginningOfDay(new Date())).getResultList();
return meetings;
}
˜q™é‡Œä¸»è¦æ³¨æ„True å’?span style="color: #008000">False 首å—æ¯å¿…™åÕd¤§å†™å…¶ä½™å°å†?
定义 Transact-SQL æœåŠ¡å™¨æ¸¸æ ‡çš„ç‰ÒŽ€§ï¼Œä¾‹å¦‚æ¸¸æ ‡çš„æ»šåŠ¨è¡Œä¸ºå’Œç”¨äºŽç”Ÿæˆæ¸¸æ ‡å¯¹å…¶˜q›è¡Œæ“作的结果集的查询。DECLARE CURSOR 接å—åŸÞZºŽ SQL-92 æ ‡å‡†çš„è¯æ³•å’Œä½¿ç”¨ä¸€¾l?Transact-SQL 扩展的è¯æ³•ã€?/font>
SQL-92 è¯æ³•
DECLARE cursor_name [ INSENSITIVE ] [ SCROLL ] CURSOR
FOR select_statement
[ FOR { READ ONLY | UPDATE [ OF column_name [ ,...n ] ] } ]
Transact-SQL 扩展è¯æ³•
DECLARE cursor_name CURSOR
[ LOCAL | GLOBAL ]
[ FORWARD_ONLY | SCROLL ]
[ STATIC | KEYSET | DYNAMIC | FAST_FORWARD ]
[ READ_ONLY | SCROLL_LOCKS | OPTIMISTIC ]
[ TYPE_WARNING ]
FOR select_statement
[ FOR UPDATE [ OF column_name [ ,...n ] ] ]
SQL-92 å‚æ•°
cursor_name
是所定义çš?Transact-SQL æœåŠ¡å™¨æ¸¸æ ‡å¿U°ã€‚cursor_name å¿…é¡»éµä»Žæ ‡è¯†½W¦è§„则。有å…Ïx ‡è¯†ç¬¦è§„则的更多信æ¯ï¼Œè¯·å‚è§ä‹Éç”¨æ ‡è¯†ç¬¦ã€?/font>
INSENSITIVE
å®šä¹‰ä¸€ä¸ªæ¸¸æ ‡ï¼Œä»¥åˆ›å»ºå°†ç”Þp¯¥æ¸¸æ ‡ä½¿ç”¨çš„æ•°æ®çš„临时å¤æœ¬ã€‚å¯¹æ¸¸æ ‡çš„æ‰€æœ‰è¯·æ±‚éƒ½ä»?tempdb ä¸çš„该äÍ时表ä¸å¾—到应½{”ï¼›å› æ¤åQŒåœ¨å¯¹è¯¥æ¸¸æ ‡˜q›è¡Œæå–æ“作时返回的数æ®ä¸ä¸åæ˜ å¯¹åŸºè¡¨æ‰€åšçš„修改åQŒåÆˆä¸”è¯¥æ¸¸æ ‡ä¸å…è®æ€¿®æ”V€‚ä‹Éç”?SQL-92 è¯æ³•æ—Óž¼Œå¦‚æžœçœç•¥ INSENSITIVEåQŒï¼ˆä»ÖM½•ç”¨æˆ·åQ‰å¯¹åŸø™¡¨æäº¤çš„åˆ é™¤å’Œæ›´æ–°éƒ½åæ˜ åœ¨åŽé¢çš„æå–ä¸ã€?/font>
SCROLL
指定所有的æå–选项åQˆFIRSTã€LASTã€PRIORã€NEXTã€RELATIVEã€ABSOLUTEåQ‰å‡å¯ç”¨ã€‚如果在 SQL-92 DECLARE CURSOR ä¸æœªæŒ‡å®š SCROLLåQŒåˆ™ NEXT 是唯一支æŒçš„æå–选项。如果指å®?SCROLLåQŒåˆ™ä¸èƒ½ä¹ŸæŒ‡å®?FAST_FORWARDã€?/font>
select_statement
æ˜¯å®šä¹‰æ¸¸æ ‡ç»“æžœé›†çš„æ ‡å‡?SELECT è¯å¥ã€‚åœ¨æ¸¸æ ‡å£°æ˜Žçš?select_statement 内ä¸å…许使用关键å?COMPUTEã€COMPUTE BYã€FOR BROWSE å’?INTOã€?/font>
如果 select_statement ä¸çš„åå¥ä¸Žæ‰€è¯äh±‚çš„æ¸¸æ ‡ç±»åž‹çš„åŠŸèƒ½å‘生冲çªåQŒåˆ™ Microsoft? SQL Server? éšæ€§åœ°ž®†æ¸¸æ ‡è{æ¢äØ“å¦ä¸€¿U类型。有å…Ïx›´å¤šä¿¡æ¯ï¼Œè¯·å‚è§éšæ€§æ¸¸æ ‡è{æ¢ã€?/font>
READ ONLY
Prevents updates made through this cursor.åœ?UPDATE æˆ?DELETE è¯å¥çš?WHERE CURRENT OF åå¥ä¸ä¸èƒ½å¼•ç”¨æ¸¸æ ‡ã€‚该选项替代è¦æ›´æ–°çš„æ¸¸æ ‡çš„é»˜è®¤åŠŸèƒ½ã€?/font>
UPDATE [OF column_name [,...n]]
å®šä¹‰æ¸¸æ ‡å†…å¯æ›´æ–°çš„列。如果指å®?OF column_name [,...n] å‚æ•°åQŒåˆ™åªå…è®æ€¿®æ”ÒŽ‰€åˆ—出的列。如果在 UPDATE ä¸æœªæŒ‡å®šåˆ—的列表åQŒåˆ™å¯ä»¥æ›´æ–°æ‰€æœ‰åˆ—ã€?/font>
Transact-SQL 扩展å‚æ•°
cursor_name
是所定义çš?Transact-SQL æœåŠ¡å™¨æ¸¸æ ‡å¿U°ã€‚cursor_name å¿…é¡»éµä»Žæ ‡è¯†½W¦è§„则。有å…Ïx ‡è¯†ç¬¦è§„则的更多信æ¯ï¼Œè¯·å‚è§ä‹Éç”¨æ ‡è¯†ç¬¦ã€?/font>
LOCAL
æŒ‡å®šè¯¥æ¸¸æ ‡çš„ä½œç”¨åŸŸå¯¹åœ¨å…¶ä¸åˆ›å»ºå®ƒçš„批处ç†ã€å˜å‚¨è¿‡½E‹æˆ–触å‘å™¨æ˜¯å±€éƒ¨çš„ã€‚è¯¥æ¸¸æ ‡å称仅在˜q™ä¸ªä½œç”¨åŸŸå†…有效。在批处ç†ã€å˜å‚¨è¿‡½E‹ã€è§¦å‘器或å˜å‚¨è¿‡½E?OUTPUT å‚æ•°ä¸ï¼Œè¯¥æ¸¸æ ‡å¯ç”±å±€éƒ¨æ¸¸æ ‡å˜é‡å¼•ç”¨ã€‚OUTPUT å‚数用于ž®†å±€éƒ¨æ¸¸æ ‡ä¼ 递回调用批处ç†ã€å˜å‚¨è¿‡½E‹æˆ–触å‘器，它们å¯åœ¨å˜å‚¨˜q‡ç¨‹¾lˆæ¢åŽç»™æ¸¸æ ‡å˜é‡æŒ‡æ´¾å‚æ•°ä½¿å…¶å¼•ç”¨æ¸¸æ ‡ã€‚é™¤é?OUTPUT å‚æ•°ž®†æ¸¸æ ‡ä¼ 递回æ¥ï¼Œå¦åˆ™æ¸¸æ ‡ž®†åœ¨æ‰¹å¤„ç†ã€å˜å‚¨è¿‡½E‹æˆ–触å‘器终æ¢æ—¶éšæ€§é‡Šæ”¾ã€‚如æž?OUTPUT å‚æ•°ž®†æ¸¸æ ‡ä¼ 递回æ¥ï¼Œæ¸¸æ ‡åœ¨æœ€åŽå¼•ç”¨å®ƒçš„å˜é‡é‡Šæ”¾æˆ–¼›Õd¼€ä½œç”¨åŸŸæ—¶é‡Šæ”¾ã€?/font>
GLOBAL
æŒ‡å®šè¯¥æ¸¸æ ‡çš„ä½œç”¨åŸŸå¯¹˜qžæŽ¥æ˜¯å…¨å±€çš„。在ç”Þp¿žæŽ¥æ‰§è¡Œçš„ä»ÖM½•å˜å‚¨˜q‡ç¨‹æˆ–批处ç†ä¸ï¼Œéƒ½å¯ä»¥å¼•ç”¨è¯¥æ¸¸æ ‡åç§°ã€‚è¯¥æ¸¸æ ‡ä»…åœ¨è„±æŽ¥æ—‰™šæ€§é‡Šæ”¾ã€?/font>
说明 如果 GLOBAL å’?LOCAL å‚数都未指定åQŒåˆ™é»˜è®¤å€¼ç”± default to local cursor æ•°æ®åº“选项的设¾|®æŽ§åˆ¶ã€‚在 SQL Server 7.0 版ä¸åQŒè¯¥é€‰é¡¹é»˜è®¤ä¸?FALSE 以与 SQL Server 早期版本相匹é…，åœ?SQL Server 早期版本ä¸æ‰€æœ‰æ¸¸æ ‡éƒ½æ˜¯å…¨å±€çš„。该选项的默认值在以åŽçš?SQL Server 版本ä¸å¯èƒ½ä¼šæ›´æ”¹ã€‚有å…Ïx›´å¤šä¿¡æ¯ï¼Œè¯·å‚è§è®¾¾|®æ•°æ®åº“选项ã€?/font>
FORWARD_ONLY
æŒ‡å®šæ¸¸æ ‡åªèƒ½ä»Žç¬¬ä¸€è¡Œæ»šåŠ¨åˆ°æœ€åŽä¸€è¡Œã€‚FETCH NEXT 是唯一å—支æŒçš„æå–选项。如果在指定 FORWARD_ONLY æ—¶ä¸æŒ‡å®š STATICã€KEYSET å’?DYNAMIC 关键å—ï¼Œåˆ™æ¸¸æ ‡ä½œä¸?DYNAMIC æ¸¸æ ‡˜q›è¡Œæ“作。如æž?FORWARD_ONLY å’?SCROLL å‡æœªæŒ‡å®šåQŒé™¤éžæŒ‡å®?STATICã€KEYSET æˆ?DYNAMIC 关键å—，å¦åˆ™é»˜è®¤ä¸?FORWARD_ONLY。STATICã€KEYSET å’?DYNAMIC æ¸¸æ ‡é»˜è®¤ä¸?SCROLL。与 ODBC å’?ADO˜q™ç±»æ•°æ®åº?API ä¸åŒåQŒSTATICã€KEYSET å’?DYNAMIC Transact-SQL æ¸¸æ ‡æ”¯æŒ FORWARD_ONLY。FAST_FORWARD å’?FORWARD_ONLY 是互斥的åQ›å¦‚果指定一个，则ä¸èƒ½æŒ‡å®šå¦ä¸€ä¸ªã€?/p>
STATIC
å®šä¹‰ä¸€ä¸ªæ¸¸æ ‡ï¼Œä»¥åˆ›å»ºå°†ç”Þp¯¥æ¸¸æ ‡ä½¿ç”¨çš„æ•°æ®çš„临时å¤æœ¬ã€‚å¯¹æ¸¸æ ‡çš„æ‰€æœ‰è¯·æ±‚éƒ½ä»?tempdb ä¸çš„该äÍ时表ä¸å¾—到应½{”ï¼›å› æ¤åQŒåœ¨å¯¹è¯¥æ¸¸æ ‡˜q›è¡Œæå–æ“作时返回的数æ®ä¸ä¸åæ˜ å¯¹åŸºè¡¨æ‰€åšçš„修改åQŒåÆˆä¸”è¯¥æ¸¸æ ‡ä¸å…è®æ€¿®æ”V€?/p>
KEYSET
æŒ‡å®šå½“æ¸¸æ ‡æ‰“å¼€æ—Óž¼Œæ¸¸æ ‡ä¸è¡Œçš„æˆå‘˜èµ„æ ¼å’Œ™åºåºå·²ç»å›ºå®šã€‚å¯¹è¡Œè¿›è¡Œå”¯ä¸€æ ‡è¯†çš„é”®é›†å†…¾|®åœ¨ tempdb 内一个称ä¸?keyset 的表ä¸ã€‚对åŸø™¡¨ä¸çš„éžé”®å€¼æ‰€åšçš„更改åQˆç”±æ¸¸æ ‡æ‰€æœ‰è€…æ›´æ”ÒŽˆ–由其它用æˆäh交）在用æˆäh»šåŠ¨æ¸¸æ ‡æ—¶æ˜¯å¯è§†çš„。其他用戯‚¿›è¡Œçš„æ’入是ä¸å¯è§†çš„（ä¸èƒ½é€šè¿‡ Transact-SQL æœåŠ¡å™¨æ¸¸æ ‡è¿›è¡Œæ’入）。如果æŸè¡Œå·²åˆ 除åQŒåˆ™å¯¹è¯¥è¡Œçš„æå–æ“作ž®†è¿”å›?@@FETCH_STATUS å€?-2ã€‚ä»Žæ¸¸æ ‡å¤–æ›´æ–°é”®å€¼ç±»ä¼égºŽåˆ 除旧行åŽæŽ¥ç€æ’入新行的æ“作。å«æœ‰æ–°å€¼çš„è¡Œä¸å¯è§†åQŒå¯¹å«æœ‰æ—§å€¼çš„行的æå–æ“作ž®†è¿”å›?@@FETCH_STATUS å€?-2。如果通过指定 WHERE CURRENT OF åå¥ç”¨æ¸¸æ ‡å®Œæˆæ›´æ–ŽÍ¼Œåˆ™æ–°å€¼å¯è§†ã€?/p>
DYNAMIC
å®šä¹‰ä¸€ä¸ªæ¸¸æ ‡ï¼Œä»¥åæ˜ åœ¨æ»šåŠ¨æ¸¸æ ‡æ—¶å¯¹¾l“果集内的行所åšçš„所有数æ®æ›´æ”V€‚行的数æ®å€¹{€é¡ºåºå’Œæˆå‘˜åœ¨æ¯‹Æ¡æå–时都会更改。动æ€æ¸¸æ ‡ä¸æ”¯æŒ ABSOLUTE æå–选项ã€?/p>
FAST_FORWARD
指定å¯ç”¨äº†æ€§èƒ½ä¼˜åŒ–çš?FORWARD_ONLYã€READ_ONLY æ¸¸æ ‡ã€‚å¦‚æžœæŒ‡å®?FAST_FORWARDåQŒåˆ™ä¸èƒ½ä¹ŸæŒ‡å®?SCROLL æˆ?FOR_UPDATE。FAST_FORWARD å’?FORWARD_ONLY 是互斥的åQ›å¦‚果指定一个，则ä¸èƒ½æŒ‡å®šå¦ä¸€ä¸ªã€?/p>
READ_ONLY
¼›æ¢é€šè¿‡è¯¥æ¸¸æ ‡è¿›è¡Œæ›´æ–°ã€‚在 UPDATE æˆ?DELETE è¯å¥çš?WHERE CURRENT OF åå¥ä¸ä¸èƒ½å¼•ç”¨æ¸¸æ ‡ã€‚该选项替代è¦æ›´æ–°çš„æ¸¸æ ‡çš„é»˜è®¤åŠŸèƒ½ã€?/p>
SCROLL_LOCKS
指定¼‹®ä¿é€šè¿‡æ¸¸æ ‡å®Œæˆçš„定ä½æ›´æ–°æˆ–定ä½åˆ 除å¯ä»¥æˆåŠŸã€‚当ž®†è¡Œè¯Õd…¥æ¸¸æ ‡ä»¥ç¡®ä¿å®ƒä»¬å¯ç”¨äºŽä»¥åŽçš„ä¿®æ”ÒŽ—¶åQŒMicrosoft? SQL Server? 会é”定这些行。如果还指定äº?FAST_FORWARDåQŒåˆ™ä¸èƒ½æŒ‡å®š SCROLL_LOCKSã€?/p>
OPTIMISTIC
指定如果行自从被è¯Õd…¥æ¸¸æ ‡ä»¥æ¥å·²å¾—到更斎ͼŒåˆ™é€šè¿‡æ¸¸æ ‡˜q›è¡Œçš„定ä½æ›´æ–°æˆ–定ä½åˆ 除ä¸æˆåŠŸã€‚当ž®†è¡Œè¯Õd…¥æ¸¸æ ‡æ—?SQL Server ä¸é”定行。相å，SQL Server 使用 timestamp 列值的比较åQŒæˆ–者如果表没有 timestamp åˆ—åˆ™ä½¿ç”¨æ ¡éªŒå€û|¼Œä»¥ç¡®å®šå°†è¡Œè¯»å…¥æ¸¸æ ‡åŽæ˜¯å¦å·²ä¿®æ”¹è¯¥è¡Œã€‚如果已修改该行åQŒå°è¯•è¿›è¡Œçš„定ä½æ›´æ–°æˆ–定ä½åˆ 除将å¤ÞpÓ|。如果还指定äº?FAST_FORWARDåQŒåˆ™ä¸èƒ½æŒ‡å®š OPTIMISTICã€?/p>
TYPE_WARNING
æŒ‡å®šå¦‚æžœæ¸¸æ ‡ä»Žæ‰€è¯äh±‚的类型éšæ€§è{æ¢äØ“å¦ä¸€¿U类型，则给客户端å‘é€è¦å‘Šæ¶ˆæ¯ã€?/p>
select_statement
æ˜¯å®šä¹‰æ¸¸æ ‡ç»“æžœé›†çš„æ ‡å‡?SELECT è¯å¥ã€‚åœ¨æ¸¸æ ‡å£°æ˜Žçš?select_statement 内ä¸å…许使用关键å?COMPUTEã€COMPUTE BYã€FOR BROWSE å’?INTOã€?/p>
如果 select_statement 内的åå¥ä¸Žæ‰€è¯äh±‚çš„æ¸¸æ ‡ç±»åž‹å†²½H，SQL Server ž®†æ¸¸æ ‡éšæ€§è{æ¢æˆå¦ä¸€¿U类型。有å…Ïx›´å¤šä¿¡æ¯ï¼Œè¯·å‚è§éšæ€§æ¸¸æ ‡è{æ¢ã€?/p>
UPDATE [OF column_name [,...n]]
å®šä¹‰æ¸¸æ ‡å†…å¯æ›´æ–°çš„列。如果æ供了 OF column_name [,...n]åQŒåˆ™åªå…è®æ€¿®æ”¹åˆ—出的列。如果在 UPDATE ä¸æœªæŒ‡å®šåˆ—的列表åQŒé™¤éžæŒ‡å®šäº† READ_ONLY òq¶å‘选项åQŒå¦åˆ™æ‰€æœ‰åˆ—å‡å¯æ›´æ–°ã€?/p>
注释
DECLARE CURSOR 定义 Transact-SQL æœåŠ¡å™¨æ¸¸æ ‡çš„ç‰ÒŽ€§ï¼Œä¾‹å¦‚æ¸¸æ ‡çš„æ»šåŠ¨è¡Œä¸ºå’Œç”¨äºŽç”Ÿæˆæ¸¸æ ‡å¯¹å…¶˜q›è¡Œæ“作的结果集的查询。OPEN è¯å¥å¡«å……¾l“果集，FETCH 从结果集˜q”回行。CLOSE è¯å¥é‡Šæ”¾ä¸Žæ¸¸æ ‡å…³è”的当剾l“果集。DEALLOCATE è¯å¥é‡Šæ”¾æ¸¸æ ‡æ‰€ä½¿ç”¨çš„资æºã€?/p>
DECLARE CURSOR è¯å¥çš„第一¿Uæ ¼å¼ä‹Éç”?SQL-92 è¯æ³•å£°æ˜Žæ¸¸æ ‡è¡Œäؓ。DECLARE CURSOR 的第二ç§æ ¼å¼ä½¿ç”¨ Transact-SQL 扩展åQŒä‹É您得以ä‹É用在 ODBCã€ADO å’?DB-Libraryçš„æ•°æ®åº“ API æ¸¸æ ‡å‡½æ•°ä¸çš„相åŒæ¸¸æ ‡¾cÕdž‹å®šä¹‰æ¸¸æ ‡ã€?/p>
ä¸èƒ½æ·äh·†˜q™ä¸¤¿Uæ ¼å¼ã€‚如果在 CURSOR 关键å—çš„å‰é¢æŒ‡å®š SCROLL æˆ?INSENSITIVE 关键å—，则ä¸èƒ½åœ¨ CURSOR å’?FOR select_statement 关键å—之间ä‹É用ä“Q何关键å—。如果在 CURSOR å’?FOR select_statement 关键å—之间指定ä“Q何关键å—åQŒåˆ™ä¸èƒ½åœ?CURSOR 关键å—çš„å‰é¢æŒ‡å®š SCROLL æˆ?INSENSITIVEã€?/p>
如果使用 Transact-SQL è¯æ³•çš?DECLARE CURSOR ä¸æŒ‡å®?READ_ONLYã€OPTIMISTIC æˆ?SCROLL_LOCKSåQŒåˆ™é»˜è®¤è®„¡½®å¦‚下åQ?
如果 SELECT è¯å¥ä¸æ”¯æŒæ›´æ–ŽÍ¼ˆæƒé™ä¸å¤ŸåQŒè®¿é—®çš„˜qœç¨‹è¡¨ä¸æ”¯æŒæ›´æ–°åQŒç‰½{‰ï¼‰åQŒåˆ™æ¸¸æ ‡æ˜?READ_ONLYã€?/p>
STATIC å’ŒFAST_FORWARD æ¸¸æ ‡é»˜è®¤ä¸?READ_ONLYã€?/p>
DYNAMIC å’?KEYSET æ¸¸æ ‡é»˜è®¤ä¸?OPTIMISTICã€?
æ¸¸æ ‡å称åªèƒ½ç”±å…¶å®?Transact-SQL è¯å¥å¼•ç”¨åQŒä¸èƒ½ç”±æ•°æ®åº?API å‡½æ•°å¼•ç”¨ã€‚ä¾‹å¦‚ï¼Œåœ¨å£°æ˜Žæ¸¸æ ‡åŽåQŒä¸èƒ½ä»Ž OLE DBã€ODBCã€ADO æˆ?DB-Library å‡½æ•°æˆ–æ–¹æ³•å¼•ç”¨æ¸¸æ ‡å¿U°ã€‚æ¸¸æ ‡è¡Œä¸èƒ½é€šè¿‡ API æå–函数或方法æå–，而åªèƒ½ç”± Transact-SQL FETCH è¯å¥æå–ã€?/p>
åœ¨å£°æ˜Žæ¸¸æ ‡åŽåQŒå¯ä½¿ç”¨ä¸‹åˆ—¾pÈ»Ÿå˜å‚¨˜q‡ç¨‹¼‹®å®šæ¸¸æ ‡çš„特性ã€?/p>
¾pÈ»Ÿå˜å‚¨˜q‡ç¨‹ æè¿°
sp_cursor_list ˜q”回当å‰åœ¨è¿žæŽ¥ä¸Šå¯è§†çš„æ¸¸æ ‡åˆ—è¡¨åŠå…¶ç‰¹æ€§ã€?
sp_describe_cursor æè¿°æ¸¸æ ‡ç‰ÒŽ€§ï¼Œæ¯”如是媘q›æ¸¸æ ‡è¿˜æ˜¯æ»šåŠ¨æ¸¸æ ‡ã€?
sp_describe_cursor_columns æè¿°æ¸¸æ ‡¾l“果集ä¸çš„列的特性ã€?
sp_describe_cursor_tables æè¿°æ¸¸æ ‡æ‰€è®‰K—®çš„基表ã€?
å˜é‡å¯ä½œä¸ºå£°æ˜Žæ¸¸æ ‡çš„ select_statement çš„ä¸€éƒ¨åˆ†ä½¿ç”¨ã€‚ç„¶è€Œï¼Œåœ¨æ¸¸æ ‡å£°æ˜Žä¹‹åŽå¯¹é‚£äº›å˜é‡çš„更改将ä¸ä¼šå¯ÒŽ¸¸æ ‡çš„æ“作产生影å“ã€?/p>
æƒé™
默认情况下，ž®?DECLARE CURSOR æƒé™æŽˆäºˆå¯ÒŽ¸¸æ ‡ä¸æ‰€ä½¿ç”¨çš„视图ã€è¡¨å’Œåˆ—æœ?SELECT æƒé™çš„ä“Q何用戗÷€?/p>
½CÞZ¾‹
A. 使用½Ž€å•æ¸¸æ ‡å’Œè¯æ³•
æ‰“å¼€è¯¥æ¸¸æ ‡æ—¶æ‰€ç”Ÿæˆçš„结果集包括 pubs æ•°æ®åº“çš„ authors 表ä¸çš„所有行和列。å¯ä»¥æ›´æ–°è¯¥æ¸¸æ ‡åQŒå¯¹è¯¥æ¸¸æ ‡æ‰€åšçš„æ‰€æœ‰æ›´æ–°å’Œåˆ é™¤å‡åœ¨æå–ä¸è¡¨çŽ°å‡ºæ¥ã€‚å› ä¸ºæ²¡æŒ‡å®š SCROLL 选项åQŒFETCH NEXT 是唯一å¯ç”¨çš„æå–选项ã€?/p>
DECLARE authors_cursor CURSOR
FOR SELECT * FROM authors
OPEN authors_cursor
FETCH NEXT FROM authors_cursor
B. ä½¿ç”¨åµŒå¥—æ¸¸æ ‡ç”ŸæˆæŠ¥è¡¨è¾“出
下例昄¡¤ºå¦‚ä½•åµŒå¥—æ¸¸æ ‡ä»¥ç”Ÿæˆå¤æ‚的报表。äØ“æ¯ä¸ªä½œè€…å£°æ˜Žå†…éƒ¨æ¸¸æ ‡ã€?/p>
SET NOCOUNT ON
DECLARE @au_id varchar(11), @au_fname varchar(20), @au_lname varchar(40),
@message varchar(80), @title varchar(80)
PRINT "-------- Utah Authors report --------"
DECLARE authors_cursor CURSOR FOR
SELECT au_id, au_fname, au_lname
FROM authors
WHERE state = "UT"
ORDER BY au_id
OPEN authors_cursor
FETCH NEXT FROM authors_cursor
INTO @au_id, @au_fname, @au_lname
WHILE @@FETCH_STATUS = 0
BEGIN
PRINT " "
SELECT @message = "----- Books by Author: " +
@au_fname + " " + @au_lname
PRINT @message
-- Declare an inner cursor based
-- on au_id from the outer cursor.
DECLARE titles_cursor CURSOR FOR
SELECT t.title
FROM titleauthor ta, titles t
WHERE ta.title_id = t.title_id AND
ta.au_id = @au_id -- Variable value from the outer cursor
OPEN titles_cursor
FETCH NEXT FROM titles_cursor INTO @title
IF @@FETCH_STATUS <> 0
PRINT " <<No Books>>"
WHILE @@FETCH_STATUS = 0
BEGIN
SELECT @message = " " + @title
PRINT @message
FETCH NEXT FROM titles_cursor INTO @title
END
CLOSE titles_cursor
DEALLOCATE titles_cursor
-- Get the next author.
FETCH NEXT FROM authors_cursor
INTO @au_id, @au_fname, @au_lname
END
CLOSE authors_cursor
DEALLOCATE authors_cursor
GO
-------- Utah Authors report --------
----- Books by Author: Anne Ringer
The Gourmet Microwave
Is Anger the Enemy?
----- Books by Author: Albert Ringer
Is Anger the Enemy?
Life Without Fear
select ename, job from emp order by substr(job, length(job)-2)
在SQL Serverä¸? order byåå¥ä¸ä‹É用substring函数:
select ename, job from emp order by substring(job, len(job)-2, 2)
select name||' is a '||type as msg from animal where ...
select name+' is a '+type as msg from animal where...
select concat(name, ' is a ', type) as msg from animal where ...
2.在SELECTè¯å¥ä¸ä‹É用æ¡ä»‰™€»è¾‘
case表达å¼å¯ä»¥é’ˆå¯ÒŽŸ¥è¯¢çš„˜q”回值执行æ¡ä»‰™€»è¾‘. å¯ä»¥¾l™case表达å¼å–别å, 使结果集更易è¯? elseåå¥æ˜¯å¯é€‰çš„, 如果没有使用else, 对于ä¸æ»¡‘›_ˆ¤æ–æ¡ä»¶çš„è¡? case表达å¼ä¼š˜q”回NULL.
select ename, sal,
case when sal<=2000 then 'UNDERPAID'
case when sal>=4000 then 'OVERPAID'
else 'OK'
end as status
from emp
CREATE DATABASE student
2.å¦‚ä½•åˆ é™¤æ•°æ®åº?/p>
DROP DATABASE student
3.如何备䆾数æ®åº“到¼‚盘文äšg
BACKUP DATABASE student to disk=´c:\1234.bak´
4.如何从ç£ç›˜æ–‡ä»¶è¿˜åŽŸæ•°æ®åº“
RESTORE DATABASE studnet FROM DISK = ´c:\1234.bak´
5.æ€Žæ ·åˆ›å¾è¡¨ï¼Ÿ
CREATE TABLE Students (
ID int IDENTITY ( 1, 1), --自增å—段,基数1,æ¥é•¿1
StudentID char (4) NOT NULL ,
Name char (10) NOT NULL ,
Age int NULL ,
Birthday datetime NULL,
CONSTRAINT PK_Students PRIMARY KEY (StudentID) --讄¡½®ä¸»é”®
)
CREATE TABLE Subjects (
ID int IDENTITY ( 1, 1), --自增å—段,基数1,æ¥é•¿1
ClassID char (4) NOT NULL ,
ClassName char (10) NOT NULL,
CONSTRAINT PK_Subjects PRIMARY KEY (ClassID) --讄¡½®ä¸»é”®
)
CREATE TABLE Scores (
ID int IDENTITY ( 1, 1), --自增å—段,基数1,æ¥é•¿1
StudentID char (4) NOT NULL ,
ClassID char (4) NOT NULL ,
Score float NOT NULL,
CONSTRAINT FK_Scores_Students FOREIGN KEY (StudentID) REFERENCES Students(StudentID), --讄¡½®å¤–é”®
CONSTRAINT FK_Scores_Subjects FOREIGN KEY (ClassID) REFERENCES Subjects(ClassID), --讄¡½®å¤–é”®
CONSTRAINT PK_Scores PRIMARY KEY (StudentID,ClassID) --讄¡½®ä¸»é”®
)
6.æ€Žæ ·åˆ é™¤è¡¨ï¼Ÿ
DROP TABLE Students
7.æ€Žæ ·åˆ›å¾è§†å›¾åQ?/p>
CREATE VIEW s_s_s
AS
SELECT Students.Name, Subjects.ClassName, Scores.Score
FROM Scores INNER JOIN
Students ON Scores.StudentID = Students.StudentID INNER JOIN
Subjects ON Scores.ClassID = Subjects.ClassID
8.æ€Žæ ·åˆ é™¤è§†å›¾åQ?/p>
DROP VIEW s_s_s
9.如何创å¾å˜å‚¨˜q‡ç¨‹?
CREATE PROCEDURE GetStudent
@age INT,
@birthday DATETIME
AS
SELECT *
FROM students
WHERE Age = @age AND Birthday = @birthday
GO
10.å¦‚ä½•åˆ é™¤å˜å‚¨˜q‡ç¨‹?
DROP PROCEDURE GetStudent
11.如何创å¾è§¦å‘å™?
CREATE TRIGGER reminder
ON Students
FOR INSERT, UPDATE, DELETE
AS
EXEC master..xp_sendmail ´MaryM´,
´Don´´t forget to print a report for the distributors.´
GO
12.å¦‚ä½•åˆ é™¤è§¦å‘å™?
DROP TRIGGER reminder
13.如何创å¾ç´¢å¼•?
CREATE UNIQUE INDEX IX_Students ON Students (Name)
14.å¦‚ä½•åˆ é™¤ç´¢å¼•?
DROP INDEX Students.IX_Students
15.æ€Žæ ·¾l™è¡¨æ·ÕdŠ å—段åQ?/p>
ALTER TABLE Students ADD Address varchar (50) NULL
16.æ€Žæ ·åˆ é™¤è¡¨ä¸æŸä¸ªå—段åQ?/p>
ALTER TABLE Students DROP COLUMN Address
17.如何讄¡½®åˆ—çš„æ ‡è¯†å±žæ€?
没找到办�/p>
18.如何åŽÀLŽ‰åˆ—çš„æ ‡è¯†å±žæ€?
没有扑ֈ°å¥½çš„æ–ÒŽ³•,åªèƒ½æ˜¯å…ˆæ·ÕdŠ 一åˆ?然åŽæŠŠæ ‡è¯†åˆ—çš„å€¼æ›´æ–°åˆ°æ–°åŠ å…¥çš„åˆ?åˆ é™¤æ ‡è¯†åˆ?å†ç”¨ä¸Žæ ‡è¯†åˆ—相åŒçš„åå—ç±»åž‹æ·»åŠ ä¸€åˆ?用å‰é¢åŠ 入的列更新该åˆ?å¦‚æžœè¯¥æ ‡è¯†åˆ—æ˜¯å…¶ä»–è¡¨çš„å¤–é”?˜q˜è¦å…ˆåˆ 除外键约æ?很麻çƒ?è°æœ‰å¥½çš„办法,˜q˜è¯·å‘Šè¯‰æˆ?
19.如何é‡è®¾æ ‡è¯†åˆ—çš„æ ‡è¯†¿Uå?
DBCC CHECKIDENT (Student, RESEED, 1)
20.æ€Žæ ·¾l™è¡¨åŠ 上主键åQ?/p>
ALTER TABLE Scores ADD CONSTRAINT PK_Scores PRIMARY KEY (StudentID,ClassID)
21.æ€Žæ ·åˆ é™¤è¡¨çš„ä¸»é”®åQ?/p>
ALTER TABLE Scores DROP CONSTRAINT PK_Scores
22.æ€Žæ ·¾l™è¡¨æ·ÕdŠ 一个外键？
ALTER TABLE Scores ADD CONSTRAINT FK_Scores_Students FOREIGN KEY (StudentID) REFERENCES Students (StudentID) ON DELETE CASCADE
23.æ€Žæ ·åˆ é™¤è¡¨çš„ä¸€ä¸ªå¤–é”®ï¼Ÿ
ALTER TABLE Scores DROP CONSTRAINT FK_Scores_Students
24.æ€Žæ ·¾l™å—ŒDµåŠ 上CHECK¾U¦æŸåQ?/p>
ALTER TABLE Students ADD CONSTRAINT CK_Students CHECK (Age > 0)
25.æ€Žæ ·åŽÀLŽ‰å—段上的CHECK¾U¦æŸåQ?/p>
ALTER TABLE Students DROP CONSTRAINT CK_Students
26.æ€Žæ ·¾l™å—ŒDµè®¾¾|®é»˜è®¤å€û|¼Ÿ
ALTER TABLE Students ADD CONSTRAINT DF_Students_Age DEFAULT (18) FOR Age
27.æ€Žæ ·¿UÕdŽ»å—段的默认å€û|¼Ÿ
ALTER TABLE Students DROP CONSTRAINT DF_Students_Age
28.修改å—段的类型åŠéžç©º¾U¦æŸ
ALTER TABLE Students ALTER COLUMN Age char (10) null
ALTER TABLE Students ALTER COLUMN Age int not null
指定å½?Transact-SQL è¯å¥äº§ç”Ÿ˜q行旉™”™è¯¯æ—¶åQŒMicrosoft® SQL Server™ 是å¦è‡ªåŠ¨å›žæ»šå½“å‰äº‹åŠ¡ã€?/p>
è¯æ³•
SET XACT_ABORT { ON | OFF }
注释
å½?SET XACT_ABORT ä¸?ON æ—Óž¼Œå¦‚æžœ Transact-SQL è¯å¥äº§ç”Ÿ˜q行旉™”™è¯¯ï¼Œæ•´ä¸ªäº‹åŠ¡ž®†ç»ˆæ¢åƈ回滚。äØ“ OFF æ—Óž¼Œåªå›žæ»šäñ”生错误的 Transact-SQL è¯å¥åQŒè€Œäº‹åŠ¡å°†¾l§ç®‹˜q›è¡Œå¤„ç†ã€‚编译错误（如è¯æ³•é”™è¯¯ï¼‰ä¸å— SET XACT_ABORT 的媄å“ã€?/p>
对于大多æ•?OLE DB æä¾›½E‹åºåQˆåŒ…æ‹?SQL ServeråQ‰ï¼Œéšæ€§æˆ–昑ּ事务ä¸çš„æ•°æ®ä¿®æ”¹è¯å¥å¿…é¡»ž®?XACT_ABORT 讄¡½®ä¸?ON。唯一ä¸éœ€è¦è¯¥é€‰é¡¹çš„情冉|˜¯æä¾›½E‹åºæ”¯æŒåµŒå¥—事务时。有å…Ïx›´å¤šä¿¡æ¯ï¼Œè¯·å‚è§?a href="javascript:hhobj_1.Click()">分布å¼æŸ¥è¯?/a>å’?a href="javascript:hhobj_2.Click()">分布å¼äº‹åŠ?/a>ã€?
SET XACT_ABORT 的设¾|®æ˜¯åœ¨æ‰§è¡Œæˆ–˜q行时设¾|®ï¼Œè€Œä¸æ˜¯åœ¨åˆ†æžæ—¶è®¾¾|®ã€?/p>
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下例å¯ÆD‡´åœ¨å«æœ‰å…¶å®?Transact-SQL è¯å¥çš„事务ä¸å‘生˜qå外键错误。在½W¬ä¸€ä¸ªè¯å¥é›†ä¸äñ”生错误，但其它è¯å¥å‡æˆåŠŸæ‰§è¡Œä¸”事务æˆåŠŸæ交。在½W¬äºŒä¸ªè¯å¥é›†ä¸ï¼ŒSET XACT_ABORT 讄¡½®ä¸?ON。这å¯ÆD‡´è¯å¥é”™è¯¯ä½¿æ‰¹å¤„熾lˆæ¢åQŒåƈ使事务回滚ã€?
CREATE TABLE t1 (a int PRIMARY KEY)
CREATE TABLE t2 (a int REFERENCES t1(a))
GO
INSERT INTO t1 VALUES (1)
INSERT INTO t1 VALUES (3)
INSERT INTO t1 VALUES (4)
INSERT INTO t1 VALUES (6)
GO
SET XACT_ABORT OFF
GO
BEGIN TRAN
INSERT INTO t2 VALUES (1)
INSERT INTO t2 VALUES (2) /* Foreign key error */
INSERT INTO t2 VALUES (3)
COMMIT TRAN
GO
SET XACT_ABORT ON
GO
BEGIN TRAN
INSERT INTO t2 VALUES (4)
INSERT INTO t2 VALUES (5) /* Foreign key error */
INSERT INTO t2 VALUES (6)
COMMIT TRAN
GO
/* Select shows only keys 1 and 3 added.
Key 2 insert failed and was rolled back, but
XACT_ABORT was OFF and rest of transaction
succeeded.
Key 5 insert error with XACT_ABORT ON caused
all of the second transaction to roll back. */
SELECT *
FROM t2
GO
DROP TABLE t2
DROP TABLE t1
GO
URL
MS SQL Server2000
com.microsoft.jdbc.sqlserver.SQLServerDriver
jdbc:microsoft:sqlserver://[ip]:[port];user=[user];passwoerd=[password]
JDBC-ODBC
sun.jdbc.odbc.JdbcOdbcDriver
jdbc:odbc:[odbcsource]
Oracle oci8
oracle.jdbc.driver.OracleDriver
jdbc:oracle:oci8:@[sid]
Oracle thin Driver
oracle.jdbc.driver.OracleDriver
jdbc:oracle:thin:@[ip]:[port]:[sid]
Cloudscape
COM.cloudscape.core.JDBCDriver
Jdbc:cloudscape:database
MySQL
org.git.mm.mysql.Driver
jdbc:mysql://ip/database?user=?&password=?
如果记录完全相åŒæ‰ç®—é‡å¤è®°å½• , 那么 : (sql server2000 下测试通过 )
select distinct * into #tmpp from person
delete from person
insert into person select * from #tmpp
drop table #tmpp
如果æœ?/span> id 主键 ( æ•°å— , 自增 1 çš„é‚£¿U?/span> ), 那么 :(sql server2000 下测试通过 )
delete from person where id not in
(select id=min(id) from person group by UserName)
2.å¤åˆ¶è¡¨ï¼ˆòq¶ä¸”å¤åˆ¶è®°å½•åQ?/strong>
select * into persontwo from personåQˆåªå¤åˆ¶è¡¨ç»“构）
insert into persontwo select UserName,Address,Content from personåQˆæ’入记录）
3.获å–表ä¸æœ€ž®æœªä½¿ç”¨çš„ID
SELECT (CASE WHEN EXISTS(SELECT * FROM person b WHERE b.Id = 1) THEN MIN(Id) + 1 ELSE 1 END) as Id
FROM person
WHERE NOT Id IN (SELECT a.Id - 1 FROM person a)
4.delete from tablea & truncate table tablea的区�/span>
truncateè¯å¥æ‰§è¡Œé€Ÿåº¦å¿?/span>,å 资æºå°‘,òq¶ä¸”åªè®°å½•é¡µåˆ 除的日志；
deleteå¯ÒŽ¯æ¡è®°å½•çš„åˆ é™¤å‡éœ€è¦è®°å½•æ—¥å¿?/span>
url=jdbc:oracle:thin:@192.168.1.110:1521:zhongxin
driver=oracle.jdbc.driver.OracleDriver
username=xxb
password=xxb
SQLServer
url=jdbc:microsoft:sqlserver://127.0.0.1:1433;DatabaseName=hagov
drive=com.microsoft.jdbc.sqlserver.SQLServerDriver
username=sa
password=sa
dialect=org.hibernate.dialect.SQLServerDialect