发表于 2009-1-5 19:48
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SQL璇硶鍙傝
鍙戝竷: 2008-7-01 14:16 | 浣滆: 缃戠粶杞浇 | 鏉ユ簮: 缃戠粶杞浇 | 鏌ョ湅: 23娆
SQL璇硶鍙傝
璧勬枡瀹氳瑷鏄寚瀵硅祫鏂欑殑鏍煎紡鍜屽舰鎬佷笅瀹氫箟鐨勮瑷锛屼粬鏄瘡涓祫鏂欏簱瑕佸缓绔嬫椂鍊欐椂棣栧厛瑕侀潰瀵圭殑锛屼妇鍑¤祫鏂欏垎鍝簺琛ㄦ牸鍏崇郴銆佽〃鏍煎唴鐨勬湁浠楹芥爮浣嶄富閿佽〃鏍煎拰琛ㄦ牸涔嬮棿浜掔浉鍙傝冪殑鍏崇郴绛夌瓑锛岄兘鏄湪寮濮嬬殑鏃跺欐墍蹇呴』瑙勫垝濂界殑銆
锛戙佸缓琛ㄦ牸锛
create table table_name(
column1 datatype [not null] [not null primary key],
column2 datatype [not null],
...锛
璇存槑锛氥
datatype --鏄祫鏂欑殑鏍煎紡锛岃瑙佽〃銆
nut null --鍙笉鍙互鍏佽璧勬枡鏈夌┖鐨勶紙灏氭湭鏈夎祫鏂欏～鍏ワ級銆
primary key --鏄湰琛ㄧ殑涓婚敭銆
锛掋佹洿鏀硅〃鏍笺
alter table table_name
add column column_name datatype
璇存槑锛氬鍔犱竴涓爮浣嶏紙娌℃湁鍒犻櫎鏌愪釜鏍忎綅鐨勮娉曘
alter table table_name
add primary key (column_name)
璇存槑锛氭洿鏀硅〃寰楃殑瀹氫箟鎶婃煇涓爮浣嶈涓轰富閿
alter table table_name
drop primary key (column_name)
璇存槑锛氭妸涓婚敭鐨勫畾涔夊垹闄ゃ
锛撱佸缓绔嬬储寮曘
create index index_name on table_name (column_name)
璇存槑锛氬鏌愪釜琛ㄦ牸鐨勬爮浣嶅缓绔嬬储寮曚互澧炲姞鏌ヨ鏃剁殑閫熷害銆
锛斻佸垹闄ゃ
drop table_name
drop index_name
浜屻佺殑璧勬枡褰㈡ datatypes
smallint
16 浣嶅厓鐨勬暣鏁般
interger
32 浣嶅厓鐨勬暣鏁般
decimal(p,s)
p 绮剧‘鍊煎拰 s 澶у皬鐨勫崄杩涗綅鏁存暟锛岀簿纭紁鏄寚鍏ㄩ儴鏈夊嚑涓暟(digits)澶у皬鍊硷紝s鏄寚灏忔暟
鐐瑰緦鏈夊嚑浣嶆暟銆傚鏋滄病鏈夌壒鍒寚瀹氾紝鍒欑郴缁熶細璁句负 p=5; s=0 銆
float
32浣嶅厓鐨勫疄鏁般
double
64浣嶅厓鐨勫疄鏁般
char(n)
n 闀垮害鐨勫瓧涓诧紝n涓嶈兘瓒呰繃 254銆
varchar(n)
闀垮害涓嶅浐瀹氫笖鍏舵渶澶ч暱搴︿负 n 鐨勫瓧涓诧紝n涓嶈兘瓒呰繃 4000銆
graphic(n)
鍜 char(n) 涓鏍凤紝涓嶈繃鍏跺崟浣嶆槸涓や釜瀛楀厓 double-bytes锛 n涓嶈兘瓒呰繃127銆傝繖涓舰鎬佹槸涓
浜嗘敮鎻翠袱涓瓧鍏冮暱搴︾殑瀛椾綋锛屼緥濡備腑鏂囧瓧銆
vargraphic(n)
鍙彉闀垮害涓斿叾鏈澶ч暱搴︿负 n 鐨勫弻瀛楀厓瀛椾覆锛宯涓嶈兘瓒呰繃 2000銆
date
鍖呭惈浜 骞翠唤銆佹湀浠姐佹棩鏈熴
time
鍖呭惈浜 灏忔椂銆佸垎閽熴佺銆
timestamp
鍖呭惈浜 骞淬佹湀銆佹棩銆佹椂銆佸垎銆佺銆佸崈鍒嗕箣涓绉掋
涓夈佽祫鏂欐搷浣 锝勶綅锝 锛坉ata manipulation language)
璧勬枡瀹氫箟濂戒箣寰屾帴涓嬫潵鐨勫氨鏄祫鏂欑殑鎿嶄綔銆傝祫鏂欑殑鎿嶄綔涓嶅涔庡鍔犺祫鏂欙紙insert)銆佹煡璇㈣祫鏂欙紙query锛夈佹洿鏀硅祫鏂欙紙update) 銆佸垹闄よ祫鏂欙紙delete锛夊洓绉嶆ā寮忥紝浠ヤ笅鍒 鍒粙缁嶄粬浠殑璇硶锛
锛戙佸鍔犺祫鏂欙細
insert into table_name (column1,column2,...)
values ( value1,value2, ...)
璇存槑锛
1.鑻ユ病鏈夋寚瀹歝olumn 绯荤粺鍒欎細鎸夎〃鏍煎唴鐨勬爮浣嶉『搴忓～鍏ヨ祫鏂欍
2.鏍忎綅鐨勮祫鏂欏舰鎬佸拰鎵濉叆鐨勮祫鏂欏繀椤诲惢鍚堛
3.table_name 涔熷彲浠ユ槸鏅 view_name銆
insert into table_name (column1,column2,...)
select columnx,columny,... from another_table
璇存槑锛氫篃鍙互缁忚繃涓涓瓙鏌ヨ锛坰ubquery锛夋妸鍒殑琛ㄦ牸鐨勮祫鏂欏～鍏ャ
锛掋佹煡璇㈣祫鏂欙細
鍩烘湰鏌ヨ
select column1,columns2,...
from table_name
璇存槑锛氭妸table_name 鐨勭壒瀹氭爮浣嶈祫鏂欏叏閮ㄥ垪鍑烘潵
select *
from table_name
where column1 = xxx
[and column2 > yyy] [or column3 <> zzz]
璇存槑锛
1.'*'琛ㄧず鍏ㄩ儴鐨勬爮浣嶉兘鍒楀嚭鏉ャ
2.where 涔嬪緦鏄帴鏉′欢寮忥紝鎶婄鍚堟潯浠剁殑璧勬枡鍒楀嚭鏉ャ
select column1,column2
from table_name
order by column2 [desc]
璇存槑锛歰rder by 鏄寚瀹氫互鏌愪釜鏍忎綅鍋氭帓搴忥紝[desc]鏄寚浠庡ぇ鍒板皬鎺掑垪锛岃嫢娌℃湁鎸囨槑锛屽垯鏄粠灏忓埌澶
鎺掑垪
缁勫悎鏌ヨ
缁勫悎鏌ヨ鏄寚鎵鏌ヨ寰楄祫鏂欐潵婧愬苟涓嶅彧鏈夊崟涓鐨勮〃鏍硷紝鑰屾槸鑱斿悎涓涓互涓婄殑
琛ㄦ牸鎵嶈兘澶熷緱鍒扮粨鏋滅殑銆
select *
from table1,table2
where table1.colum1=table2.column1
璇存槑锛
1.鏌ヨ涓や釜琛ㄦ牸涓叾涓 column1 鍊肩浉鍚岀殑璧勬枡銆
2.褰撶劧涓や釜琛ㄦ牸鐩镐簰姣旇緝鐨勬爮浣嶏紝鍏惰祫鏂欏舰鎬佸繀椤荤浉鍚屻
3.涓涓鏉傜殑鏌ヨ鍏跺姩鐢ㄥ埌鐨勮〃鏍煎彲鑳戒細寰堝涓
鏁村悎鎬х殑鏌ヨ锛
select count (*)
from table_name
where column_name = xxx
璇存槑锛
鏌ヨ绗﹀悎鏉′欢鐨勮祫鏂欏叡鏈夊嚑绗斻
select sum(column1)
from table_name
璇存槑锛
1.璁＄畻鍑烘诲拰锛屾墍閫夌殑鏍忎綅蹇呴』鏄彲鏁扮殑鏁板瓧褰㈡併
2.闄ゆ浠ュ杩樻湁 avg() 鏄绠楀钩鍧囥乵ax()銆乵in()璁＄畻鏈澶ф渶灏忓肩殑鏁村悎鎬ф煡璇€
select column1,avg(column2)
from table_name
group by column1
having avg(column2) > xxx
璇存槑锛
1.group by: 浠olumn1 涓轰竴缁勮绠 column2 鐨勫钩鍧囧煎繀椤诲拰 avg銆乻um绛夋暣鍚堟ф煡璇㈢殑鍏抽敭瀛
