Oracle stored procedures and functions

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One 、 stored procedure

A stored procedure is a named PL/SQL Data blocks , Stored in Oracle In the database , Can be called by user . Stored procedures can contain parameters , There can be no parameters , It usually has no return value . Stored procedures are pre compiled code , There is no need to compile again when calling again , Therefore, the operation efficiency of the program is very high .

1、 Creation of stored procedures

The grammar is as follows

create [or replace]  The process of 
[< Parameters 1> inioutin out < Parameter type >[ The default value is |:= Initial value ]]
[,< Parameters 2> inioutin out < Parameter type >[ The default value is |:= Initial value ],...]
isias
[ Local variable declaration ]
begin
 Program statement sequence 
[exception]
 Exception handling statement sequence 
end  The process of 

The parameters are described as follows ：
1、or replace Optional parameters , Indicates that if the process to be created already exists in the database , Delete the original process first , Re establish the process , Or cover the original process .
2、 If there are parameters in the process , You need to use “inioutin out” keyword . If it's an input parameter , Then the parameter is followed by “in” keyword , It means to accept the value passed by the external process ; If it's an output parameter , Then the parameter is followed by “out” keyword , Indicates that this parameter will be copied in the process , And pass it to the process outside ; If it is “in out” Keyword indicates that the parameter has the characteristics of input parameter , It also has the characteristics of output parameters . The default is in Parameters , That is, if you don't write it, it defaults to in Parameters .
3、 Parameter type cannot specify length , Just give the type .
4、 Variables defined in the local variable declaration are only valid in this procedure .
5、 Local variable declaration , The definition and use of program statement sequence and exception handling statement sequence are the same as in the previous chapter PL/SQL block .

2、 Calling and deleting stored procedures

After a stored procedure is created , Exist in the form of compilation oracle In the database , Can be in sql plus Medium or pl/sql Call in block .
1、 stay sql plus Calling stored procedure in
The grammar is as follows ：

execute  The process of  [ Parameter sequence ]

among execute It can be abbreviated as exec.
2、 stay pl/sql Call stored procedure in block
Write the process name directly to other pl/sql Block can be called , There is no need to use execute command .
3、 Deletion of stored procedure
Deleting a stored procedure is similar to deleting a table , The basic syntax is as follows .

drop procdure  The process of 

3、 Use of stored procedures

1、 Stored procedure without parameters

1、 Create a stored procedure , towards student Insert a record in the table

create or replace procedure pro_stu is 
begin
	insert into student<id,name,class> values<10,' Zhang San ',' the fifth class '>;
	commit;
	dbms_output.put_line<' Insert a new record ！！！'>;
end pro_stu;

The above stored procedure has been successfully created , But it didn't execute , The execution statement is as follows .

exec pro_stu;

It's on it exec Command execution , We can also do that PL/SQL Directly call in the block , The grammar is as follows .

begin
	pro_stu;
end;

2、 belt in Parameter stored procedure
Use in Parameters can input data to program units in stored procedures , Provide parameter values when calling , Read by stored procedure . This mode is the default parameter mode . Here is an example .

2、 Create a stored procedure , Receive values from the outside , Judge whether the value is greater than zero in the stored procedure and display .

create or replace procedure pro_decide<
	var_num in number
> is
begin
	if var_num>=0 then
		dbms_output.put_line<' The parameter passed in is greater than or equal to 0'>;
	else
		dbms_output.put_line<' The parameter passed in is less than 0'>;
	end if;
end pro_decide;

Execute stored procedures

exec pro_decide<3>;

Results show ：
The parameter passed in is greater than or equal to 0

3、 Enter a number , Inquire about student Is there this number in the table , If yes, the name of the corresponding student will be displayed , If not, it will prompt that there is no corresponding student .

create or replace procedure pro_show<
	var_stuid in student.id%type	-- Definition in Parameters 
> is
	var_name student.name%type;	-- Define stored procedure internal variables 
	no_result exception;
begin
	select name into var_name from student where id = var_stuid;	-- Value 
	if sql%found then
		dbms_output.put_line<' The student name inquired is ：' || var_name>;	-- Show 
	end if;
		when no_data_found then
			dbms_output.put_line<' There is no student corresponding to this number '>;	-- Error handling 
	end pro_show;

Execute stored procedures .

exec pro_show<10>

4、 Create a stored procedure , To the data table student Insert a record in .

create or replace procedure pro_add<
	var_id in number,
	var_name in varchar2,
	var_class in varchar2> is
begin
	insert into student values<var_id,var_name,var_class>;	-- insert record 
	commit;
	dbms_output.put_line<' Insert a new record ！！！'>;
end pro_add;

Execute stored procedures

exec pro_add<10,' Zhang San ',' the fifth class '>;

5、 Enter a number , Inquire about student Is there this number in the table , If yes, return the name of the corresponding student , If not, it will prompt that there is no corresponding student .

We use in Is to display the student's name , Now we want to return the student's name and use out, The grammar is as follows

create or replace procedure pro_show1<
	var_id in student.id%type,	-- Definition in Parameters 
	var_name out student.name%type	-- Definition out Parameters 
> is
	no_result exception;
begin
	select name init var_name from student where id = var_id;	-- Value 
exception
	when no_data_found then
		dbms_output.put_line<' There is no student corresponding to this number '>;	-- Error handling 
end pro_show1;

Call contains out The stored procedure of parameters needs to declare a variable of corresponding type in advance , Then it is used to receive .

variable var_name varchar2<10>;
exec pro_show1<10,:var_name>;

At call time , Use “：” Followed by the variable name .

4、 Query of stored procedure

The query of stored procedure needs to use data dictionary user_source, The grammar is as follows

select distinct name from user_source where type=upper('procedure');

The above statement queries the names of all stored procedures under the current user .
Besides , We can also query the contents of stored procedures , The query statement is shown below .

select text from user_source where name = upper('pro_aa');

Two 、 function

The above stored procedure has input parameters and output parameters , But there is no return value , Functions are very similar to stored procedures , It can also be stored in oracle In the database PL/SQL Code block , But there is a return value , You can define a frequently used function as a function , Just like the function of the system （ For example, case conversion , Find the absolute value and other functions ） The use of .

1、 Function creation

The basic syntax format of function creation is as follows .

create or replace function  Function name 
[< Parameters 1> inioutin out < Parameter type >[ The default value is |:= Initial value ]]
return  Return data type 
isias
[ Local variable declaration ]
begin
 Program statement sequence 
[exception]
 Exception handling statement sequence 
end  The process of 

The parameters are described as follows .
1、or replace Optional parameters , Indicates that if the function to be created already exists in the database , Delete the original function first , Then rebuild the function , Or overwrite the original function .
2、 If there are parameters in the process , You need to use “inioutin out” keyword . If it's an input parameter , Then the parameter is followed by “in” keyword , It means to accept the value passed by the external process ; If it's an output parameter , Then the parameter is followed by “out” keyword , Indicates that this parameter will be copied in the process , And pass it to the process outside ; If it is “in out” Keyword indicates that the parameter has the characteristics of input parameter , It also has the characteristics of output parameters . The default is in Parameters , That is, if you don't write it, it defaults to in Parameters .
3、 Parameter type cannot specify length , Just give the type .
4、 The return value type of the function is required .
5、 The variables defined in the local variable declaration are only valid in this function .
6、 Local variable declaration 、 Definition and use of program statement sequence and exception handling statement sequence PL/SQL block .
In the main program of the function , You have to use return Statement returns the final function value , And the data type of the return value should be the same as the type specified when declaring .

## 2、 The creation and use of implicit cursors 
> Different from the display cursor , Implicit cursors are automatically created by the system , Used for processing DML sentence （ for example insert、update、delete Such as instruction ） Or select Query the single row data returned , In this case, the implicit cursor is a pointer to the buffer . There is no need to declare when using 、 Open and close , So you don't need open、fetch、close Such operation instructions . Implicit cursors are also described above 4 Species attribute , When using, you need to add the default name of the implicit cursor in front of the attribute SQL, Therefore, implicit cursors are also called SQL The cursor .

###  1、 take student The age of Zhang San's students in the table increases 10 year , Then use an implicit cursor %rowcount Number of employees involved in attribute output 
```go
begin
	update student set age=age+10	-- Increase in age 10
	where name = ' Zhang San ';
	if sql%notfound then	-- Whether there are qualified records 
		dbms_output.put_line<' No eligible students '>;
	else
		dbms_output.put_line<' The number of eligible students is ：' || sql%rowcount>;
	end if;
end;

2、 Function call and deletion

The calling method of function is basically the same as that of system built-in function . Can be directly in SQL plus Use in , It can also be used in stored procedures .
Deleting functions is similar to deleting stored procedures , The grammar is as follows ：

drop function  Function name 

3、 Use of functions

1、 Create a function , If it is an even number, calculate its square , If it is an odd number, calculate its square root

create or replace function fun_cal
	<var_num number>	-- Declare function parameters 
	return number		-- Declare the function return type 
is
i int:=2;
begin
	if mod<var_num,2>=0 then	-- Judge parity 
		return power<var_num,i>;	-- Return square 
	flse
		return round<sqrt<var_num>,2>;	-- Return square root 
	end if;
end fun_cal;

4、 Function query

In actual use, it is often necessary to query the existing functions in the database or the contents of a certain function , The method used is similar to that of stored procedures , You also need to use a data dictionary user_source, The query statements used are as follows .

select distinct name from user_source where type=upper('function');

The above statement queries the names of all user-defined functions under the current user .
Besides , We can also query the content of the function , The query statement is shown below .

select text from user_source where name=upper('fun_cal') and type=upper('function')

3、 ... and 、 summary

The relevant contents here have not been sorted out yet , The article continues to be updated later , Recommended collection .

The commands involved in the article must be typed several times each like me , Only in the process of knocking can you find out whether you really master the command .

You can search by wechat 【 Xiaoqi JAVA interview 】 First time reading , reply 【 Information 】 Access to benefits , reply 【 project 】 Get the source code of the project , reply 【 The resume template 】 Get resume template , reply 【 Learning Roadmap 】 Get a learning roadmap .