Oracle Procedure (PL/SQL) 实践归纳

基本格式：

例：

create or replace procedure validateUser(USERNAME in VARCHAR2, USERPASSWORD in VARCHAR2, USERTYPE OUT VARCHAR2, VALID OUT CHAR) //头声明，参数以“参数名 in/out 类型”格式声明

 is //过程开始

v_temp number; //变量声明，格式为“变量名 类型”，“；”结尾

begin //过程体开始
  select count(1) INTO v_temp from MANAGER //一种赋值的方式是用select into的形式
  where ma_name=USERNAME and ma_password=USERPASSWORD; //写完一个语句用“；”结尾
 
  if(v_temp=0) then //这里是“if-then-else-end if”的格式
  usertype:='not legal user'; //直接赋值
  valid:='0';
  else
  select ma_type into usertype from manager
  where ma_name=USERNAME and ma_password=USERPASSWORD;
  valid:='1';
 
  end if; 
 
end ; //过程体结束

 

 

           

为适应select * 的情况，在变量声明时，可以使用variable_name tbl_name%rowtype;这样的形式，意思相似于variable_name为由tbl_name中各个column名为属性构成的struct.

 

 

%的奇特用途一：

在Oracle Tutorial中有这样一段话：

Instead of specifying a data type, one can also refer to the data type of a table column (so-called anchored declaration). For example, EMP.Empno%TYPE refers to the data type of the column Empno in the relation EMP. Instead of a single variable, a record can be declared that can store a complete tuple from a given table (or query result). For example, the data type DEPT%ROWTYPE specifies a record suitable to store all attribute values of a complete row from the table DEPT. Such records are typically used in combination with a cursor. A field in a record can be accessed using <record name>.<column name>, for example, DEPT.Deptno.

简单说来就是在声明变量时，不只可以用Oracle的类型名定义，还可以用表中的字段相应类型定义。比如：

v_name tblName.colName%Type; 这一句的意思就是将v_name定义成表tblName中colName列的类型；而它后面的%Type是说明这种用法的固定写法。

另外一种是在变量声明时，可以使用：

variable_name tbl_name%rowtype;

这样的形式，意思相似于variable_name是一个由tbl_name中各个column名为属性构成的struct. （比如为适应select *  into variable_name的情况）。其中%rowtype是这种用法的固定写法。而要调用这个struct的属性，则直接以variable_name.col_name就可以了（这个与一般编程语言一样）。

 

 

 

 

有关于Exception：

Oracle Procedure里的Excpetion部分很像Java里的catch块，即实现了出现异常后的处理。例如：

exception
when NO_DATA_FOUND then //是when而不是if
o_dataExist:=0;

格式“when – then”表示在某种异常的情况下应该进行的操作。 When后面的异常情况见表：

Oracle Exception Name	Oracle Error	Explanation
DUP_VAL_ON_INDEX	ORA-00001	You tried to execute an INSERT or UPDATE statement that has created a duplicate value in a field restricted by a unique index.
TIMEOUT_ON_RESOURCE	ORA-00051	You were waiting for a resource and you timed out.
TRANSACTION_BACKED_OUT	ORA-00061	The remote portion of a transaction has rolled back.
INVALID_CURSOR	ORA-01001	You tried to reference a cursor that does not yet exist. This may have happened because you've executed a FETCH cursor or CLOSE cursor before OPENing the cursor.
NOT_LOGGED_ON	ORA-01012	You tried to execute a call to Oracle before logging in.
LOGIN_DENIED	ORA-01017	You tried to log into Oracle with an invalid username/password combination.
NO_DATA_FOUND	ORA-01403	You tried one of the following: 1.       You executed a SELECT INTO statement and no rows were returned. 2.       You referenced an uninitialized row in a table. 3.       You read past the end of file with the UTL_FILE package.
TOO_MANY_ROWS	ORA-01422	You tried to execute a SELECT INTO statement and more than one row was returned.
ZERO_DIVIDE	ORA-01476	You tried to divide a number by zero.
INVALID_NUMBER	ORA-01722	You tried to execute an SQL statement that tried to convert a string to a number, but it was unsuccessful.
STORAGE_ERROR	ORA-06500	You ran out of memory or memory was corrupted.
PROGRAM_ERROR	ORA-06501	This is a generic "Contact Oracle support" message because an internal problem was encountered.
VALUE_ERROR	ORA-06502	You tried to perform an operation and there was an error on a conversion, truncation, or invalid constraining of numeric or character data.
CURSOR_ALREADY_OPEN	ORA-06511	You tried to open a cursor that is already open.

除了上面所示的，还有其他的Exception可以用when others来捕获。