PLSQL语言基础

结构：
DECLARE //标记声明部分
//此处用来定义常量，变量，类型和游标

BEGIN //标记程序体开头部分
//编写各种PL/SQL语句，函数，存储过程

EXCEPTION //异常处理开始
//编写异常处理代码

END; //程序体结束

PL/SQL可以独立编译并存储在数据库中，有4种可存储的程序：函数，存储过程，包和触发器
例如：
SYS AS SYSDBA@ORCL>SET SERVEROUTPUT ON;
SYS AS SYSDBA@ORCL>DECLARE
2 VAR_DEPNAME VARCHAR2(100);
3 BEGIN
4 SELECT DEPARTMENT_NAME INTO VAR_DEPNAME
5 FROM HR.DEPARTMENTS WHERE DEPARTMENT_ID=270;
6 DBMS_OUTPUT.PUT_LINE(VAR_DEPNAME);
7 END;
8 /
声明变量和常量：
DECLARE
<变量名1> <数据类型1>;
<变量名N> <数据类型N>;

PL/SQL常用的数据类型：
BLOB 二进制大对象，可以用来存储图像和文档等二进制数据
BOOLEAN 布尔数据类型，支持TRUE/FALSE
CHAR 固定长度字符串
CLOB 字符大对象，最大保存4G字符数据
DATE 存储全部日期的固定长度字符串
LONG 可变长度字符串
NUMBER 可变长度数值
RAW 二进制数据的可变长度字符串
VARCHAR2 可变长度字符串

声明常量：
<常量名> CONSTANT <数据类型> := <值>
SYS AS SYSDBA@ORCL>SET SERVEROUTPUT ON;
SYS AS SYSDBA@ORCL>DECLARE
2 CONVERSION CONSTANT VARCHAR2(20) :='1.0';
3 BEGIN
4 DBMS_OUTPUT.PUT_LINE(CONVERSION);
5 END;
6 /

声明变量：
<变量名> <数据类型> [(宽度):=<初始值>]
SYS AS SYSDBA@ORCL>SET SERVEROUTPUT ON
SYS AS SYSDBA@ORCL>DECLARE
2 DEPNAME VARCHAR2(20):='HR DEPARTMENT';
3 BEGIN
4 DBMS_OUTPUT.PUT_LINE(DEPNAME);
5 END;
6 /
HR DEPARTMENT

使用赋值语句
SYS AS SYSDBA@ORCL>SET SERVEROUTPUT ON;
SYS AS SYSDBA@ORCL>DECLARE
2 BOOKNAME VARCHAR2(50);
3 BEGIN
4 BOOKNAME:='ORACLE BOOKS';
5 DBMS_OUTPUT.PUT_LINE(BOOKNAME);
6 END;
7 /
ORACLE BOOKS

使用条件语句(IF)
IF<条件表达式> THEN
<执行语句>....<执行语句>
[ELSIF<条件表达式> THEN
<执行语句>....<执行语句>
...
ELSE
<执行语句>]
END IF;
SYS AS SYSDBA@ORCL>SET SERVEROUTPUT ON;
SYS AS SYSDBA@ORCL>DECLARE
2 NUM INTEGER:=-11;
3 BEGIN
4 IF NUM<0 THEN
5 DBMS_OUTPUT.PUT_LINE('FUSHU');
6 ELSIF NUM>0 THEN
7 DBMS_OUTPUT.PUT_LINE('ZHENGSHU');
8 ELSE
9 DBMS_OUTPUT.PUT_LINE('0');
10 END IF;
11 END;
12 /
FUSHU

分支语句CASE
CASE <变量>
WHEN <表达式1> THEN 值1
WHEN <表达式n> THEN 值n
ELSE 值n + 1
END;

SYS AS SYSDBA@ORCL>SET SERVEROUTPUT ON;
SYS AS SYSDBA@ORCL>DECLARE
2 VARDAY INTEGER:=3;
3 RESULT VARCHAR2(20);
4 BEGIN
5 RESULT:=CASE VARDAY
6 WHEN 1 THEN '1'
7 WHEN 2 THEN '2'
8 WHEN 3 THEN '3'
9 ELSE '0'
10 END;
11 DBMS_OUTPUT.PUT_LINE(RESULT);
12 END;
13 /
3

循环语句LOOP....EXIT....END
LOOP
<程序块1>
IF<条件表达式>THEN
EXIT
END IF
<程序块2>
END LOOP;

SYS AS SYSDBA@ORCL>SET SERVEROUTPUT ON;
SYS AS SYSDBA@ORCL>DECLARE
2 V_NUM INTEGER:=1;
3 V_SUM INTEGER:=0;
4 BEGIN
5 LOOP
6 V_SUM:=V_SUM+V_NUM;
7 DBMS_OUTPUT.PUT_LINE(V_NUM);
8 IF V_NUM=4 THEN
9 EXIT;
10 END IF ;
11 DBMS_OUTPUT.PUT_LINE('+');
12 V_NUM:=V_NUM+1;
13 END LOOP;
14 DBMS_OUTPUT.PUT_LINE('=');
15 DBMS_OUTPUT.PUT_LINE(V_SUM);
16 END;
17 /
1
+
2
+
3
+
4
=
10

循环语句LOOP....EXIT...WHEN...END

LOOP
<程序块1>
EXIT WHEN <条件表达式>
<程序块2>
END LOOP;

SYS AS SYSDBA@ORCL>SET SERVEROUTPUT ON;
SYS AS SYSDBA@ORCL>DECLARE
2 V_NUM INTEGER:=1;
3 V_SUM INTEGER:=0;
4 BEGIN
5 LOOP
6 V_SUM:=V_SUM+V_NUM;
7 DBMS_OUTPUT.PUT_LINE(V_NUM);
8 EXIT WHEN V_NUM=4;
9 DBMS_OUTPUT.PUT_LINE('+');
10 V_NUM:=V_NUM+1;
11 END LOOP;
12 DBMS_OUTPUT.PUT_LINE('=');
13 DBMS_OUTPUT.PUT_LINE(V_SUM);
14 END;
15 /
1
+
2
+
3
+
4
=
10

循环语句WHILE....LOOP....END LOOP

WHILE<条件表达式>
LOOP
<程序块>
END LOOP;

SYS AS SYSDBA@ORCL>SET SERVEROUTPUT ON;
SYS AS SYSDBA@ORCL>DECLARE
2 V_NUM INTEGER:=1;
3 V_SUM INTEGER:=0;
4 BEGIN
5 WHILE V_NUM<=4
6 LOOP
7 V_SUM:=V_SUM+V_NUM;
8 DBMS_OUTPUT.PUT_LINE(V_NUM);
9 IF V_NUM<4 THEN
10 DBMS_OUTPUT.PUT_LINE('+');
11 END IF;
12 V_NUM:=V_NUM+1;
13 END LOOP;
14 DBMS_OUTPUT.PUT_LINE('=');
15 DBMS_OUTPUT.PUT_LINE(V_SUM);
16 END;
17 /
1
+
2
+
3
+
4
=
10

循环语句FOR...IN...LOOP...END LOOP
FOR <循环变量> IN <初始值>...<终止值>
LOOP
<程序块>
END LOOP;

SYS AS SYSDBA@ORCL>SET SERVEROUTPUT ON
SYS AS SYSDBA@ORCL>DECLARE
2 V_NUM INTEGER;
3 V_SUM INTEGER:=0;
4 BEGIN
5 FOR V_NUM IN 1..4
6 LOOP
7 V_SUM:=V_SUM+V_NUM;
8 DBMS_OUTPUT.PUT_LINE(V_NUM);
9 IF V_NUM<4 THEN
10 DBMS_OUTPUT.PUT_LINE('+');
11 END IF ;
12 END LOOP;
13 DBMS_OUTPUT.PUT_line('=');
14 DBMS_OUTPUT.PUT_LINE(V_SUM);
15 END;
16 /
1
+
2
+
3
+
4
=
10

数值型函数：
ABS函数：
SYS AS SYSDBA@ORCL>SET SERVEROUTPUT ON;
SYS AS SYSDBA@ORCL>BEGIN
2 DBMS_OUTPUT.PUT_LINE(ABS(-450));
3 END;
4 /
450

CEIL函数
SYS AS SYSDBA@ORCL>BEGIN
2 DBMS_OUTPUT.PUT_LINE(CEIL(0));
3 DBMS_OUTPUT.PUT_LINE(CEIL(-112.74));
4 DBMS_OUTPUT.PUT_LINE(CEIL(116.34));
5 END;
6 /
0
-112
117

FLOOR函数
SYS AS SYSDBA@ORCL>SET SERVEROUTPUT ON;
SYS AS SYSDBA@ORCL>BEGIN
2 DBMS_OUTPUT.PUT_LINE(FLOOR(116.34));
3 DBMS_OUTPUT.PUT_LINE(FLOOR(-112.74));
4 DBMS_OUTPUT.PUT_LINE(FLOOR(0));
5 END;
6 /
116
-113
0

POWER 函数
SYS AS SYSDBA@ORCL>SET SERVEROUTPUT ON
SYS AS SYSDBA@ORCL>BEGIN
2 DBMS_OUTPUT.PUT_LINE(POWER(10,3));
3 END;
4 /
1000
ROUND函数
SYS AS SYSDBA@ORCL>SET SERVEROUTPUT ON
SYS AS SYSDBA@ORCL>BEGIN
2 DBMS_OUTPUT.PUT_LINE(ROUND(123.45,2));
3 DBMS_OUTPUT.PUT_LINE(ROUND(123.45,0));
4 DBMS_OUTPUT.PUT_LINE(ROUND(123.45,-1));
5 END;
6 /
123.45
123
120

字符型函数
ASCII函数：(返回首字母的ASCII值)
SYS AS SYSDBA@ORCL>SET SERVEROUTPUT ON
SYS AS SYSDBA@ORCL>BEGIN
2 DBMS_OUTPUT.PUT_LINE(ASCII('ABC'));
3 END;
4 /
65

PL/SQL procedure successfully completed.

Elapsed: 00:00:00.05
SYS AS SYSDBA@ORCL>BEGIN
2 DBMS_OUTPUT.PUT_LINE(ASCII('BC'));
3 END;
4 /
66

LENGTH函数（返回指定字段的长度）
SYS AS SYSDBA@ORCL>SELECT DEPARTMENT_NAME,LENGTH(DEPARTMENT_NAME) FROM HR.DEPARTMENTS WHERE ROWNUM<3;

DEPARTMENT_NAME LENGTH(DEPARTMENT_NAME)
------------------------------ -----------------------
Administration 14
Marketing 9

UPPER函数：（将字符串转换为大写字母）
SYS AS SYSDBA@ORCL>SET SERVEROUTPUT ON
SYS AS SYSDBA@ORCL>BEGIN
2 DBMS_OUTPUT.PUT_LINE(UPPER('abc'));
3 END;
4 /
ABC

日期型函数：
SYSDATE函数
SYS AS SYSDBA@ORCL>SET SERVEROUTPUT ON;
SYS AS SYSDBA@ORCL>BEGIN
2 DBMS_OUTPUT.PUT_LINE(SYSDATE);
3 END;
4 /

TO_CHAR函数(将日期型数据DATE，转换成FORMAT指定格式的字符串) TO_CHAR(DATE,FORMAT)
SYS AS SYSDBA@ORCL>SET SERVEROUTPUT ON
SYS AS SYSDBA@ORCL>BEGIN
2 DBMS_OUTPUT.PUT_LINE(TO_CHAR(SYSDATE));
3 END;
4 /
22-DEC-14

LAST_DAY函数（返回指定日期所在月的最后一天）
SYS AS SYSDBA@ORCL>BEGIN
2 DBMS_OUTPUT.PUT_LINE(LAST_DAY(SYSDATE));
3 END;
4 /
31-DEC-14

TO_DATE函数TO_DATE(STRING,FORMAT)将字符串STRING转换成以FORMAT指定格式的日期型数据
1 BEGIN
2 DBMS_OUTPUT.PUT_LINE(TO_DATE('2010-2-5','YYYY-MM-DD'));
3* END;
SYS AS SYSDBA@ORCL>/
05-FEB-10

MONTHS_BETWEEN函数(返回DATE1减去DATE2得到的月份整数)
SYS AS SYSDBA@ORCL>DECLARE
2 DATE1 VARCHAR2(20):='2010-05-05';
3 DATE2 VARCHAR2(20):='2010-10-05';
4 BEGIN
5 DBMS_OUTPUT.PUT_LINE(MONTHS_BETWEEN(TO_DATE(DATE2,'YYYY-MM-DD'),TO_DATE(DATE1,'YYYY-MM-DD')));
6 END;
7 /
5

统计函数：
COUNT()统计总数量
SYS AS SYSDBA@ORCL>SELECT COUNT(DEPARTMENT_ID) FROM HR.DEPARTMENTS;

COUNT(DEPARTMENT_ID)
--------------------
27

MAX函数，统计最大值
SYS AS SYSDBA@ORCL>SELECT MAX(DEPARTMENT_ID) FROM HR.DEPARTMENTS;

MAX(DEPARTMENT_ID)
------------------
270

MIN函数(统计最小值)
SYS AS SYSDBA@ORCL>SELECT MIN(DEPARTMENT_ID) FROM HR.DEPARTMENTS;

MIN(DEPARTMENT_ID)
------------------
10

AVG()函数统计平均值：
SYS AS SYSDBA@ORCL>SELECT AVG(DEPARTMENT_ID) FROM HR.DEPARTMENTS;

AVG(DEPARTMENT_ID)
------------------
140
SUM()求总和
SYS AS SYSDBA@ORCL>SELECT sum(DEPARTMENT_ID) FROM HR.DEPARTMENTS;

SUM(DEPARTMENT_ID)
------------------
3780

异常处理：
EXCEPTION
WHEN <异常情况名> THEN //异常情况名由ORACLE系统定义好的名字
异常处理代码
WHEN <异常情况名> THEN
异常处理代码
WHEN OTHERS THEN
异常处理代码

SYS AS SYSDBA@ORCL>DECLARE
2 X NUMBER;
3 BEGIN
4 X:='ABC';
5 EXCEPTION
6 WHEN VALUE_ERROR THEN
7 DBMS_OUTPUT.PUT_LINE('1223323');
8 END;
9 /
1223323