oracle中值集限定词为灰色,《Oracle从入门到精通》读书笔记第四章 SQL语言基础之一...
4.1?SQL語言概述
4.1.1?SQL語言的特點
1、集合性
2、統一性
3、易于移植性
4.1.2?SQL語言的分類
1、數據查詢語言(DQL)-?select語句，查詢數據
2、數據操縱語言(DML)-?insert、update和delete語句，改變數據
3、事務控制語言(TCL)-?commit、rollback和savepoint語句，維護數據一致性
4、數據定義語言(DDL)-?create、alter和drop語句，改變數據庫對象
5、數據控制語言(DCL)-?grant和revoke語句，權限授予和回收
4.1.3?SQL語言的編寫規則
1、關鍵字不區分大小寫
2、字符值區分大小寫
3、以分號作為結束符
4、2?用戶模式
4.2.1?模式與模式對象
模式是一個數據庫對象的集合
模式為一個數據庫用戶所有，并且具有與該用戶相同的名稱。
模式對象是由用戶創建的邏輯結構，用以存儲或引用數據。比如段，約束，視圖，同義詞，過程，程序包等。
不屬于某個用戶所擁有的數據庫對象就不能稱之為模式對象，比如角色，表空間，目錄等。
4.2.2?實例模式SCOTT
SQL>?conn?scott/tiger
Connected.
SQL>?select?table_name?from?user_tables;
TABLE_NAME
------------------------------
DEPT
EMP
BONUS
SALGRADE
SQL>?select?table_name?from?dba_tables?where?owner='SCOTT';
TABLE_NAME
------------------------------
DEPT
EMP
BONUS
SALGRADE
4.3?檢索數據
語法格式：
select?{[distinct|all]column|*}
[into?table_name]
from?{tables|views|other?select}
[where?conditions]
[group?by?columns]
[having?conditions]
[order?by?columns]
4.3.1?簡單查詢
1、檢索所有的(*)
SQL>?select?*?from?scott.dept;
DEPTNO?DNAME??????????LOC
----------?--------------?-------------
10?ACCOUNTING?????NEW?YORK
20?RESEARCH???????DALLAS
30?SALES??????????CHICAGO
40?OPERATIONS?????BOSTON
SQL>?select?*?from?scott.dept,scott.salgrade;
DEPTNO?DNAME??????????LOC????????????????GRADE??????LOSAL??????HISAL
----------?--------------?-------------?----------?----------?----------
10?ACCOUNTING?????NEW?YORK???????????????1????????700???????1200
10?ACCOUNTING?????NEW?YORK???????????????2???????1201???????1400
10?ACCOUNTING?????NEW?YORK???????????????3???????1401???????2000
10?ACCOUNTING?????NEW?YORK???????????????4???????2001???????3000
10?ACCOUNTING?????NEW?YORK???????????????5???????3001???????9999
20?RESEARCH???????DALLAS?????????????????1????????700???????1200
20?RESEARCH???????DALLAS?????????????????2???????1201???????1400
20?RESEARCH???????DALLAS?????????????????3???????1401???????2000
20?RESEARCH???????DALLAS?????????????????4???????2001???????3000
20?RESEARCH???????DALLAS?????????????????5???????3001???????9999
30?SALES??????????CHICAGO????????????????1????????700???????1200
DEPTNO?DNAME??????????LOC????????????????GRADE??????LOSAL??????HISAL
----------?--------------?-------------?----------?----------?----------
30?SALES??????????CHICAGO????????????????2???????1201???????1400
30?SALES??????????CHICAGO????????????????3???????1401???????2000
30?SALES??????????CHICAGO????????????????4???????2001???????3000
30?SALES??????????CHICAGO????????????????5???????3001???????9999
40?OPERATIONS?????BOSTON?????????????????1????????700???????1200
40?OPERATIONS?????BOSTON?????????????????2???????1201???????1400
40?OPERATIONS?????BOSTON?????????????????3???????1401???????2000
40?OPERATIONS?????BOSTON?????????????????4???????2001???????3000
40?OPERATIONS?????BOSTON?????????????????5???????3001???????9999
20?rows?selected.
2、檢索指定的列
SQL>?select?job,ename,empno?from?emp;
JOB???????ENAME???????????EMPNO
---------?----------?----------
CLERK?????SMITH????????????7369
SALESMAN??ALLEN????????????7499
SALESMAN??WARD?????????????7521
MANAGER???JONES????????????7566
SALESMAN??MARTIN???????????7654
MANAGER???BLAKE????????????7698
MANAGER???CLARK????????????7782
ANALYST???SCOTT????????????7788
PRESIDENT?KING?????????????7839
SALESMAN??TURNER???????????7844
CLERK?????ADAMS????????????7876
JOB???????ENAME???????????EMPNO
---------?----------?----------
CLERK?????JAMES????????????7900
ANALYST???FORD?????????????7902
CLERK?????MILLER???????????7934
14?rows?selected.
SQL>?select?rowid,job,ename?from?emp;
ROWID??????????????JOB???????ENAME
------------------?---------?----------
AAAR3xAAEAAAACXAAA?CLERK?????SMITH
AAAR3xAAEAAAACXAAB?SALESMAN??ALLEN
AAAR3xAAEAAAACXAAC?SALESMAN??WARD
AAAR3xAAEAAAACXAAD?MANAGER???JONES
AAAR3xAAEAAAACXAAE?SALESMAN??MARTIN
AAAR3xAAEAAAACXAAF?MANAGER???BLAKE
AAAR3xAAEAAAACXAAG?MANAGER???CLARK
AAAR3xAAEAAAACXAAH?ANALYST???SCOTT
AAAR3xAAEAAAACXAAI?PRESIDENT?KING
AAAR3xAAEAAAACXAAJ?SALESMAN??TURNER
AAAR3xAAEAAAACXAAK?CLERK?????ADAMS
ROWID??????????????JOB???????ENAME
------------------?---------?----------
AAAR3xAAEAAAACXAAL?CLERK?????JAMES
AAAR3xAAEAAAACXAAM?ANALYST???FORD
AAAR3xAAEAAAACXAAN?CLERK?????MILLER
14?rows?selected.
3、帶有表達式的select子句
SQL>?select?sal*(1+0.1),sal?from?emp;
SAL*(1+0.1)????????SAL
-----------?----------
880????????800
1760???????1600
1375???????1250
3272.5???????2975
1375???????1250
3135???????2850
2695???????2450
3300???????3000
5500???????5000
1650???????1500
1210???????1100
SAL*(1+0.1)????????SAL
-----------?----------
1045????????950
3300???????3000
1430???????1300
14?rows?selected.
4、為列指定別名
可以使用as關鍵字，也可以直接指定
SQL>?select?empno?as?"員工編號"?from?emp;
員工編號
------------
7369
7499
7521
7566
7654
7698
7782
7788
7839
7844
7876
員工編號
------------
7900
7902
7934
14?rows?selected.
SQL>?select?empno?"員工編號"?from?emp;
員工編號
------------
7369
7499
7521
7566
7654
7698
7782
7788
7839
7844
7876
員工編號
------------
7900
7902
7934
14?rows?selected.
5、顯示不重復記錄
使用distinct關鍵字去除重復記錄
SQL>?select?distinct?job?from?emp;
JOB
---------
CLERK
SALESMAN
PRESIDENT
MANAGER
ANALYST
4.3.2?篩選查詢
語法格式：
select?columns_list
from?table_name
where?conditional_expression
1、比較篩選
基本比較篩選有以下6種情況:A=B
A!B或A<>B
A>B
A>=B
A
A<=B
SQL>?select?empno,ename,sal?from?emp?where?sal>1500;
EMPNO?ENAME?????????????SAL
----------?----------?----------
7499?ALLEN????????????1600
7566?JONES????????????2975
7698?BLAKE????????????2850
7782?CLARK????????????2450
7788?SCOTT????????????3000
7839?KING?????????????5000
7902?FORD?????????????3000
7?rows?selected.
特殊比較篩選有以下兩種情況：
A{operator}ANY(B):A與B中任何一個元素進行operator運算符的比較，只要有一個比較值為true，就返回數據行
A{operator}ALL(B):A與B中所有元素進行operator運算符的比較，只有所有元素比較值為true，才返回數據行
SQL>?select?empno,ename,sal?from?emp?where?sal<>all(3000,950,800);
EMPNO?ENAME?????????????SAL
----------?----------?----------
7499?ALLEN????????????1600
7521?WARD?????????????1250
7566?JONES????????????2975
7654?MARTIN???????????1250
7698?BLAKE????????????2850
7782?CLARK????????????2450
7839?KING?????????????5000
7844?TURNER???????????1500
7876?ADAMS????????????1100
7934?MILLER???????????1300
10?rows?selected.
2、使用特殊關鍵字篩選
(1)like關鍵字：字符串匹配
常用通配符：
_：代表任意一個字符
%：代表任意數量字符
SQL>?select?empno,ename,job?from?emp?where?ename?like?'S%';
EMPNO?ENAME??????JOB
----------?----------?---------
7369?SMITH??????CLERK
7788?SCOTT??????ANALYST
SQL>?select?empno,ename,job?from?emp?where?ename?not?like?'S%';
EMPNO?ENAME??????JOB
----------?----------?---------
7499?ALLEN??????SALESMAN
7521?WARD???????SALESMAN
7566?JONES??????MANAGER
7654?MARTIN?????SALESMAN
7698?BLAKE??????MANAGER
7782?CLARK??????MANAGER
7839?KING???????PRESIDENT
7844?TURNER?????SALESMAN
7876?ADAMS??????CLERK
7900?JAMES??????CLERK
7902?FORD???????ANALYST
EMPNO?ENAME??????JOB
----------?----------?---------
7934?MILLER?????CLERK
12?rows?selected.
(2)in關鍵字：測試一個數據值是否匹配一組目標值中的一個
SQL>?select?empno,ename,job?from?emp?where?job?in('PRESIDENT','MANAGER','ANALYST');
EMPNO?ENAME??????JOB
----------?----------?---------
7566?JONES??????MANAGER
7698?BLAKE??????MANAGER
7782?CLARK??????MANAGER
7788?SCOTT??????ANALYST
7839?KING???????PRESIDENT
7902?FORD???????ANALYST
6?rows?selected.
SQL>?select?empno,ename,job?from?emp?where?job?not?in('PRESIDENT','MANAGER','ANALYST');
EMPNO?ENAME??????JOB
----------?----------?---------
7369?SMITH??????CLERK
7499?ALLEN??????SALESMAN
7521?WARD???????SALESMAN
7654?MARTIN?????SALESMAN
7844?TURNER?????SALESMAN
7876?ADAMS??????CLERK
7900?JAMES??????CLERK
7934?MILLER?????CLERK
8?rows?selected.
(3)between關鍵字：返回某一個數據值是否位于兩個給的的值之間
SQL>?select?empno,ename,sal?from?emp?where?sal?between?2000?and?3000;
EMPNO?ENAME?????????????SAL
----------?----------?----------
7566?JONES????????????2975
7698?BLAKE????????????2850
7782?CLARK????????????2450
7788?SCOTT????????????3000
7902?FORD?????????????3000
SQL>?select?empno,ename?sal?from?emp?where?sal?not?between?2000?and?3000;
EMPNO?SAL
----------?----------
7369?SMITH
7499?ALLEN
7521?WARD
7654?MARTIN
7839?KING
7844?TURNER
7876?ADAMS
7900?JAMES
7934?MILLER
9?rows?selected.
(4)is?null?關鍵字：檢測是否為空
SQL>?select?empno,ename,comm?from?emp?where?comm?is?null;
EMPNO?ENAME????????????COMM
----------?----------?----------
7369?SMITH
7566?JONES
7698?BLAKE
7782?CLARK
7788?SCOTT
7839?KING
7876?ADAMS
7900?JAMES
7902?FORD
7934?MILLER
10?rows?selected.
3、邏輯篩選：AND,OR,NOT
SQL>?select?empno,ename,sal?from?emp?where?sal>=2000?and?sal<=3000;
EMPNO?ENAME?????????????SAL
----------?----------?----------
7566?JONES????????????2975
7698?BLAKE????????????2850
7782?CLARK????????????2450
7788?SCOTT????????????3000
7902?FORD?????????????3000
SQL>?select?empno,ename,sal?from?emp?where?sal<2000?or?sal>3000;
EMPNO?ENAME?????????????SAL
----------?----------?----------
7369?SMITH?????????????800
7499?ALLEN????????????1600
7521?WARD?????????????1250
7654?MARTIN???????????1250
7839?KING?????????????5000
7844?TURNER???????????1500
7876?ADAMS????????????1100
7900?JAMES?????????????950
7934?MILLER???????????1300
9?rows?selected.
4.3.3?分組查詢
語法格式：
select?columns_list
from?table_name
[where?conditional_expression]
group?by?columns_list
SQL>?select?deptno,job?from?emp?group?by?deptno,job?order?by?deptno;
DEPTNO?JOB
----------?---------
10?CLERK
10?MANAGER
10?PRESIDENT
20?ANALYST
20?CLERK
20?MANAGER
30?CLERK
30?MANAGER
30?SALESMAN
9?rows?selected.
SQL>?select?deptno?as?部門編號,avg(sal)?as?平均工資?from?emp?group?by?deptno;
部門編號?平均工資
------------?------------
30???1566.66667
20?????????2175
10???2916.66667
group?by列表需要包括非聚集表達式內的所有列或者與選擇列表表達式完全匹配
SQL>?select?deptno,avg(sal)?from?emp?group?by?deptno?having?avg(sal)<2000;
DEPTNO???AVG(SAL)
----------?----------
30?1566.66667
4.3.4?排序查詢
語法格式：
select?columns_list
from?table_name
[where?conditional_expression]
[group?by?columns_list]
order?by?{order_by_expression[asc|desc]}[,...n]
SQL>?select?deptno,empno,ename?from?emp?order?by?deptno,empno;
DEPTNO??????EMPNO?ENAME
----------?----------?----------
10???????7782?CLARK
10???????7839?KING
10???????7934?MILLER
20???????7369?SMITH
20???????7566?JONES
20???????7788?SCOTT
20???????7876?ADAMS
20???????7902?FORD
30???????7499?ALLEN
30???????7521?WARD
30???????7654?MARTIN
DEPTNO??????EMPNO?ENAME
----------?----------?----------
30???????7698?BLAKE
30???????7844?TURNER
30???????7900?JAMES
14?rows?selected.
4.3.5?多表關聯查詢
1、表別名
SQL>?select?e.empno?as??員工編號,e.ename?as?員工名稱,d.dname?as?部門
2??from?emp?e,dept?d
3??where?e.deptno=d.deptno
4??and?e.job='MANAGER';
員工編號?員工名?部門
------------?----------?--------------
7782?CLARK??????ACCOUNTING
7566?JONES??????RESEARCH
7698?BLAKE??????SALES
2、內連接
語法格式：
select?columns_list
from?table_name1?[inner]?join?table_name2
on?join_condition;
SQL>?select?e.empno,e.ename,d.dname
2??from?emp?e?inner?join?dept?d
3??on?e.deptno=d.deptno;
EMPNO?ENAME??????DNAME
----------?----------?--------------
7782?CLARK??????ACCOUNTING
7839?KING???????ACCOUNTING
7934?MILLER?????ACCOUNTING
7566?JONES??????RESEARCH
7902?FORD???????RESEARCH
7876?ADAMS??????RESEARCH
7369?SMITH??????RESEARCH
7788?SCOTT??????RESEARCH
7521?WARD???????SALES
7844?TURNER?????SALES
7499?ALLEN??????SALES
EMPNO?ENAME??????DNAME
----------?----------?--------------
7900?JAMES??????SALES
7698?BLAKE??????SALES
7654?MARTIN?????SALES
14?rows?selected.
3、外連接
分類：
左外連接：關鍵字為left?outer?join或left?join，會包含左表中不滿足連接條件的數據行
右外連接：關鍵字為right?outer?join或right?join，會包含右表中不滿足連接條件的數據行
完全外連接：關鍵字為full?outer?join或full?join
SQL>?insert?into?emp(empno,ename,job)?values(9527,'EAST','SALESMAN');
1?row?created.
SQL>?select?e.empno,e.ename,e.job,d.deptno,d.dname
2??from?emp?e?left?join?dept?d
3??on?e.deptno=d.deptno
4??;
EMPNO?ENAME??????JOB???????????DEPTNO?DNAME
----------?----------?---------?----------?--------------
7934?MILLER?????CLERK?????????????10?ACCOUNTING
7839?KING???????PRESIDENT?????????10?ACCOUNTING
7782?CLARK??????MANAGER???????????10?ACCOUNTING
7902?FORD???????ANALYST???????????20?RESEARCH
7876?ADAMS??????CLERK?????????????20?RESEARCH
7788?SCOTT??????ANALYST???????????20?RESEARCH
7566?JONES??????MANAGER???????????20?RESEARCH
7369?SMITH??????CLERK?????????????20?RESEARCH
7900?JAMES??????CLERK?????????????30?SALES
7844?TURNER?????SALESMAN??????????30?SALES
7698?BLAKE??????MANAGER???????????30?SALES
EMPNO?ENAME??????JOB???????????DEPTNO?DNAME
----------?----------?---------?----------?--------------
7654?MARTIN?????SALESMAN??????????30?SALES
7521?WARD???????SALESMAN??????????30?SALES
7499?ALLEN??????SALESMAN??????????30?SALES
9527?EAST???????SALESMAN
15?rows?selected.
SQL>?select?e.empno,e.ename,e.job,d.deptno,d.dname
2??from?emp?e?right?join?dept?d
3??on?e.deptno=d.deptno;
EMPNO?ENAME??????JOB???????????DEPTNO?DNAME
----------?----------?---------?----------?--------------
7782?CLARK??????MANAGER???????????10?ACCOUNTING
7934?MILLER?????CLERK?????????????10?ACCOUNTING
7839?KING???????PRESIDENT?????????10?ACCOUNTING
7566?JONES??????MANAGER???????????20?RESEARCH
7369?SMITH??????CLERK?????????????20?RESEARCH
7788?SCOTT??????ANALYST???????????20?RESEARCH
7902?FORD???????ANALYST???????????20?RESEARCH
7876?ADAMS??????CLERK?????????????20?RESEARCH
7521?WARD???????SALESMAN??????????30?SALES
7844?TURNER?????SALESMAN??????????30?SALES
7499?ALLEN??????SALESMAN??????????30?SALES
EMPNO?ENAME??????JOB???????????DEPTNO?DNAME
----------?----------?---------?----------?--------------
7900?JAMES??????CLERK?????????????30?SALES
7654?MARTIN?????SALESMAN??????????30?SALES
7698?BLAKE??????MANAGER???????????30?SALES
40?OPERATIONS
15?rows?selected.
SQL>?select?e.empno,e.ename,e.job,d.deptno,d.dname
2??from?emp?e?full?join?dept?d
3??on?e.deptno=d.deptno;
EMPNO?ENAME??????JOB???????????DEPTNO?DNAME
----------?----------?---------?----------?--------------
7369?SMITH??????CLERK?????????????20?RESEARCH
7499?ALLEN??????SALESMAN??????????30?SALES
7521?WARD???????SALESMAN??????????30?SALES
7566?JONES??????MANAGER???????????20?RESEARCH
7654?MARTIN?????SALESMAN??????????30?SALES
7698?BLAKE??????MANAGER???????????30?SALES
7782?CLARK??????MANAGER???????????10?ACCOUNTING
7788?SCOTT??????ANALYST???????????20?RESEARCH
7839?KING???????PRESIDENT?????????10?ACCOUNTING
7844?TURNER?????SALESMAN??????????30?SALES
7876?ADAMS??????CLERK?????????????20?RESEARCH
EMPNO?ENAME??????JOB???????????DEPTNO?DNAME
----------?----------?---------?----------?--------------
7900?JAMES??????CLERK?????????????30?SALES
7902?FORD???????ANALYST???????????20?RESEARCH
7934?MILLER?????CLERK?????????????10?ACCOUNTING
9527?EAST???????SALESMAN
40?OPERATIONS
16?rows?selected.
4、自然連接
使用natural?join關鍵字，很少使用，不能為列指定限定詞(即表名或者表的別名)
SQL>?select?empno,ename,job,dname
2??from?emp?natural?join?dept
3??where?sal?>?2000;
EMPNO?ENAME??????JOB???????DNAME
----------?----------?---------?--------------
7782?CLARK??????MANAGER???ACCOUNTING
7839?KING???????PRESIDENT?ACCOUNTING
7902?FORD???????ANALYST???RESEARCH
7788?SCOTT??????ANALYST???RESEARCH
7566?JONES??????MANAGER???RESEARCH
7698?BLAKE??????MANAGER???SALES
6?rows?selected.
5、自連接
SQL>?select?em2.ename?manager,em1.ename?employee
2??from?emp?em1?left?join?emp?em2
3??on?em1.mgr=em2.empno
4??order?by?em1.mgr;
MANAGER????EMPLOYEE
----------?----------
JONES??????FORD
JONES??????SCOTT
BLAKE??????JAMES
BLAKE??????TURNER
BLAKE??????MARTIN
BLAKE??????WARD
BLAKE??????ALLEN
CLARK??????MILLER
SCOTT??????ADAMS
KING???????CLARK
KING???????BLAKE
MANAGER????EMPLOYEE
----------?----------
KING???????JONES
FORD???????SMITH
EAST
KING
15?rows?selected.
6、交叉連接
不需要任何連接條件的連接，關鍵字cross?join,執行結果是一個笛卡爾積。
語法格式：
select?columns_list
from?table_name1?cross?join?table_name2
SQL>?select?count(*)
2??from?dept?cross?join?emp;
COUNT(*)
----------
60
4.4?Oracle常用系統函數
4.4.1?字符類函數
1、ascii(c)函數和chr(i)函數
字符與ascii碼的轉換
SQL>?select?ascii('Z')Z,ascii('H')H,ascii('D')D,ascii('?')space?from?dual;
Z??????????H??????????D??????SPACE
----------?----------?----------?----------
90?????????72?????????68?????????32
SQL>?select?chr(90),chr(72),chr(68),chr(32)S?from?dual;
C?C?C?S
-?-?-?-
Z?H?D
2、concat(s1,s2)函數
將字符串s2連接到字符串s1后面
SQL>?select?concat('hello?','world')?information?from?dual;
INFORMATION
-----------
hello?world
3、initcap(s)函數
將字符數s的每個單詞的第一個字母大寫，其他字母小寫。
SQL>?select?initcap('oh?my?god!')?information?from?dual;
INFORMATIO
----------
Oh?My?God!
4、instr(s1,s2[,i][,j])函數
返回字符s2在字符串s1中第j次出現時的位置，搜索從字符串s1的第i個字符開始，當沒有發現要查找的字符時，返回0。其中s1和s2均為字符串，i和j均為整數，默認為1。
SQL>?select?instr('oracle?11g','1',3,2)?abc?from?dual;
ABC
----------
9
5、length(s)函數
返回字符串s的長度
SQL>?select?e.empno,e.ename,d.dname
2??from?emp?e?inner?join?dept?d
3??on?e.deptno=d.deptno
4??where?length(e.ename)>5;
EMPNO?ENAME??????DNAME
----------?----------?--------------
7654?MARTIN?????SALES
7844?TURNER?????SALES
7934?MILLER?????ACCOUNTING
6、lower(s)函數和upper(s)函數
分別返回字符串s的小寫形式和大寫形式，這兩個函數經常出現在where子句中。
SQL>?select?empno,ename,job?from?emp?where?lower(job)?like?'s%';
EMPNO?ENAME??????JOB
----------?----------?---------
7499?ALLEN??????SALESMAN
7521?WARD???????SALESMAN
7654?MARTIN?????SALESMAN
7844?TURNER?????SALESMAN
9527?EAST???????SALESMAN
7、ltrim(s1,s2)函數，rtrim(s1,s2)函數和trim(s1,s2)函數
分別用來刪除字符串s1左邊的字符串s2，刪除字符串s1右邊的字符串s2，刪除字符串s1左右兩端字符串s2，如果不指定字符串s2，則刪除相應方位的空格。
SQL>?select?ltrim('###east###','#')?ltrim?from?dual;
LTRIM
-------
east###
SQL>?select?rtrim('###east###','#')?rtrim?from?dual;
RTRIM
-------
###east
SQL>?select?trim('#'?from?'###east###')?from?dual;
TRIM
----
east
8、replace(s1,s2[,s3])函數
使用s3字符串替換出現在s1字符串中的所有s2字符串，并返回替換后的新字符串，其中，s3字符串默認為空字符串。
SQL>?select?replace('bad?luck?bad?girl','bad','good')?from?dual;
REPLACE('BADLUCKBAD
-------------------
good?luck?good?girl
9、substr(s,i,[j])函數
從字符串s的第i個位置開始截取長度為j的子字符串。如果省略參數j，則直接截取到尾部。
SQL>?select?substr('messagebox',8,3)?from?dual;
SUB
---
box
4.4.2?數字類函數
1、ceil(n)函數
大于或等于數值n的最小整數，天花板函數
SQL>?select?ceil(7.3),ceil(7),ceil(-7.3)?from?dual;
CEIL(7.3)????CEIL(7)?CEIL(-7.3)
----------?----------?----------
8??????????7?????????-7
2、round(n1,n2)函數
返回舍入小數點右邊n2位的n1的值，n2默認為0
SQL>?select?round(3.1415926,2)?from?dual;
ROUND(3.1415926,2)
------------------
3.14
3、power(n1,n2)函數
返回n1的n2次方
SQL>?select?power(2,3)?from?dual;
POWER(2,3)
----------
8
4.4.3?日期和時間類函數
1、sysdate()函數
返回系統當前的日期
SQL>?select?sysdate?from?dual;
SYSDATE
------------
01-DEC-13
2、add_months(d,i)函數
返回日期d加上i個月之后的結果
SQL>?select?add_months(sysdate,6)?from?dual;
ADD_MONTHS(S
------------
01-JUN-14
4.4.4?轉換類函數
1、to_char(x[,format])函數
將表達式轉換成字符串，format表示字符串格式
SQL>?select?sysdate,to_char(sysdate,'YYYY-MM-DD')?from?dual;
SYSDATE??????TO_CHAR(SY
------------?----------
01-DEC-13????2013-12-01
2、to_number(s[,format[lan]])函數
返回字符串s代表的數字
SQL>?select?to_number('18','xxx')?from?dual;
TO_NUMBER('18','XXX')
---------------------
24
4.4.5?集合類函數
SQL>?select?count(empno)?as?sum,round(avg(sal),2)?as?avg?from?emp;
SUM????????AVG
----------?----------
14????2073.21
4.5?子查詢的用法
4.5.1?子查詢
SQL>?select?empno,ename,job?from?emp
2??where?deptno=(select?deptno?from?dept?where?dname='RESEARCH');
EMPNO?ENAME??????JOB
----------?----------?---------
7369?SMITH??????CLERK
7566?JONES??????MANAGER
7788?SCOTT??????ANALYST
7876?ADAMS??????CLERK
7902?FORD???????ANALYST
SQL>?select?empno,ename,job
2??from?emp?join?dept
3??on?emp.deptno=dept.deptno
4??where?dept.dname='RESEARCH';
EMPNO?ENAME??????JOB
----------?----------?---------
7566?JONES??????MANAGER
7902?FORD???????ANALYST
7876?ADAMS??????CLERK
7369?SMITH??????CLERK
7788?SCOTT??????ANALYST
子查詢相對對表關聯查詢要慢一些。
使用子查詢時，應注意一下規則：
子查詢必須用括號()括起來
子查詢中不能包括order?by子句
子查詢允許嵌套多層，但不能超過255層
子查詢分為單行子查詢，多行子查詢和關聯子查詢
4.5.2?單行子查詢
返回一行數據的子查詢語句。當在where子句中引用單行子查詢時，可以使用單行比較運算符(=，>,=和<>)。
SQL>?select?empno,ename,sal?from?emp
2??where?sal>(select?min(sal)?from?emp)?and?sal
EMPNO?ENAME?????????????SAL
----------?----------?----------
7499?ALLEN????????????1600
7521?WARD?????????????1250
7566?JONES????????????2975
7654?MARTIN???????????1250
7698?BLAKE????????????2850
7782?CLARK????????????2450
7788?SCOTT????????????3000
7844?TURNER???????????1500
7876?ADAMS????????????1100
7900?JAMES?????????????950
7902?FORD?????????????3000
EMPNO?ENAME?????????????SAL
----------?----------?----------
7934?MILLER???????????1300
12?rows?selected.
4.5.3?多行子查詢
返回多行數據的子查詢語句。當在where子句中使用多行子查詢時，必須使用多行運算符(in，any，all)
1、使用in運算符
使用in運算符時，外查詢會嘗試與子查詢結果中的任何一個結果進行匹配，只要有一個匹配成功，則外查詢返回當前檢索的記錄。
SQL>?select?empno,ename,job?from?emp
2??where?deptno?in?(select?deptno?from?dept?where?dname<>'SALES');
EMPNO?ENAME??????JOB
----------?----------?---------
7782?CLARK??????MANAGER
7839?KING???????PRESIDENT
7934?MILLER?????CLERK
7566?JONES??????MANAGER
7902?FORD???????ANALYST
7876?ADAMS??????CLERK
7369?SMITH??????CLERK
7788?SCOTT??????ANALYST
8?rows?selected.
2、使用any運算符
any運算符必須與單行比較運算符結合使用，并且返回行只要匹配子查詢的任何一個結果即可。
SQL>?select?empno,ename,sal?from?emp
2??where?sal?>?any(select?sal?from?emp?where?deptno=10)?and?deptno<>10;
EMPNO?ENAME?????????????SAL
----------?----------?----------
7788?SCOTT????????????3000
7902?FORD?????????????3000
7566?JONES????????????2975
7698?BLAKE????????????2850
7499?ALLEN????????????1600
7844?TURNER???????????1500
6?rows?selected.
3、使用all運算符
all運算符必須與單行運算符結合使用，并且返回行必須匹配所有子查詢結果。
SQL>?select?deptno,ename,sal?from?emp
2??where?sal?>?all(select?sal?from?emp?where?deptno=30);
DEPTNO?ENAME?????????????SAL
----------?----------?----------
20?JONES????????????2975
20?SCOTT????????????3000
20?FORD?????????????3000
10?KING?????????????5000
4.5.4?關聯子查詢
內查詢和外查詢相互關聯
SQL>?select?empno,ename,sal
2??from?emp?f
3??where?sal>(select?avg(sal)?from?emp?where?job=f.job)
4??order?by?job;
EMPNO?ENAME?????????????SAL
----------?----------?----------
7876?ADAMS????????????1100
7934?MILLER???????????1300
7566?JONES????????????2975
7698?BLAKE????????????2850
7499?ALLEN????????????1600
7844?TURNER???????????1500
6?rows?selected.
4.6?操作數據庫
4.6.1?插入數據(insert語句)
1、單條插入數據
語法格式：
insert?into?table_name(column_name1[,column_name2]...)]
value(express1[,express2]...)
SQL>?insert?into?dept(deptno,dname,loc)
2??values(88,'design','beijing');
1?row?created.
SQL>?insert?into?jobs
2??values('PRO','程序員',5000,10000);
1?row?created.
2、批量插入數據
語法格式：
insert?into?table_name?[(column_name1[,column_name2]...)]?select?subquery
SQL>?create?table?jobs_temp(
2??job_id?varchar2(10)?primary?key,
3??job_title?varchar2(35)?not?null,
4??min_salary?number(6),
5??max_salary?number(6));
Table?created.
SQL>?desc?jobs_temp;
Name??????????????????????????????????????Null?????Type
-----------------------------------------?--------?----------------------------
JOB_ID????????????????????????????????????NOT?NULL?VARCHAR2(10)
JOB_TITLE?????????????????????????????????NOT?NULL?VARCHAR2(35)
MIN_SALARY?????????????????????????????????????????NUMBER(6)
MAX_SALARY?????????????????????????????????????????NUMBER(6)
SQL>?insert?into?jobs_temp
2??select?*?from?jobs
3??where?jobs.max_salary>10000;
9?rows?created.
4.6.2?更新數據(update語句)
語法格式：
update?table_name
set?{column_name1=express1[,column_name2=express2...]
|(column_name1[,column_name2...])=(selectsubquery)}
[where?condition]
SQL>?update?emp
2??set?sal=sal*1.2
3??where?job='SALESMAN';
4?rows?updated.
SQL>?update?emp
2??set?sal=(select?avg(sal)?from?emp?where?job='MANAGER')
3??where?sal<2000;
8?rows?updated.
4.6.3?刪除數據(delete語句和truncate語句)
1、delete語句
刪除數據庫中的所有記錄和指定范圍的記錄
語法格式：
delete?from?table_name
[where?condition]
SQL>?delete?from?jobs
2??where?job_id='PRO';
1?row?deleted.
2、truncate語句
刪除表中的所有記錄，比delete快，不產生回滾記錄，無法使用rollback語句撤銷。
SQL>?truncate?table?jobs_temp;
Table?truncated.
總結
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