MySQL 05 stored procedure

One 、 Learning goals

1. Understand the concept of stored procedures
2. Will create 、 modify 、 Delete 、 View stored procedures
3. Master the flow control statements of stored procedures

Two 、 stored procedure

2.1 Why do I need to use stored procedures

problem ：

• Online bookstore Application , Different publishers need to count their book sales every month , And hope to store the data in the temporary table for analysis .

Basic steps

1. Use DROP Statement to delete existing temporary table data
2. Set the publisher name
3. Get the number of the publishing house according to the name of the publishing house
4. Query the sales data of the current month according to the publishing house number , And use the query results to create a new temporary table

analysis ：

• Each step requires a SQL sentence
• Check the book sales of different publishers , You need to dynamically set the name of the publishing house
• Perform the same operation for data analysis every month
• In order to solve this problem more conveniently , have access to MySQL Of stored procedure

2.2 What is stored procedure

• Stored Procedure

• It's a group of people who do certain functions SQL Statement set

• After compilation, it is saved in the database

• By specifying the name of the stored procedure and giving the value of the parameter

• MySQL5.0 The version starts to support stored procedures , Make the database engine more flexible and powerful

• With parameters , You can also return the result

• It can contain data manipulation statements 、 Variable 、 Logic control statements, etc

  

2.3 Advantages and disadvantages of stored procedures

advantage

1. Reduce network traffic
2. Improve execution speed
3. Reduce the number of database connections
4. High safety
5. High reusability

shortcoming

• Poor portability

Experience

• In practical application development , Decide whether to use stored procedures according to business requirements , For particularly complex data processing in applications , You can choose stored procedures to implement
• for example ： Complex report statistics , Joint queries involving multiple conditions and tables

3、 ... and 、 Create stored procedure

3.1 Grammar and characteristics ：

grammar ：

CREATE PROCEDURE  The process of  ([ Process parameters [,…]])
    [ characteristic ] # optional , Used to set the behavior of stored procedures 
     Stored procedure body   

Common features ：

characteristic	explain
LANGUAGE SQL	Represents stored procedure language , Default SQL
{CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA}	Indicates the type of work to be done by the stored procedure The default value is CONTAINS SQL
SQL SECURITY { DEFINER | INVOKER }	Specify the execution permission of the stored procedure The default value is DEFINER •DEFINDER： Use the permissions of the creator •INVOKER： With the authority of the executor
COMMENT ‘string’	Annotation information of stored procedure

Example ：

• Writing stored procedures , Output the total number of patients

# Delete... If it exists 
drop procedure if exists proc_patient_countPatient; 
# Create stored procedure 
create procedure proc_patient_countPatient()
begin # The process body starts  
    select count(0) as totalCount from patient;
end # The process body ends  

problem ：

• The compiler treats it as normal SQL Statement processing , Error will be reported in compilation , What do I do ？

3.2 Declaration statement separator

• Use DELIMITER Keyword set the delimiter to “$$” or “//”

DELIMITER $$  
# perhaps   
DELIMITER //

• Revert to the default separator “;”

DELIMITER ; 

3.3 Identification of process body

• When defining the body of a stored procedure , Need to identify the beginning and end

BEGIN
    # … 
END
DELIMITER ; #END after , You have to use DELIMITER The delimiter set in the statement is end 

matters needing attention ：

// If no delimiter is declared , The compiler will treat it as normal SQL Statement processing , An error will be reported during compilation 
// Proper use ： First use DELIMITER Keyword declares the separator of the current segment , Finally, restore the delimiter to the default character 

Example ：

# Delete... If it exists 
drop procedure if exists proc_patient_countPatient; 
delimiter//      # Declaration separator 
create procedure proc_patient_countPatient()
begin # The process body starts  
    select count(0) as totalCount from patient;
end// # The process body ends  
delimiter;       # Restore the default delimiter 

# call 
call proc_patient_countPatient();

3.4 Stored procedure parameter settings

Define the parameters of the stored procedure

grammar ：

[IN | OUT | INOUT]  Parameter name   data type 

Example ：

DELIMITER //      # Declaration separator 
CREATE PROCEDURE proc_patient_countPatient2(OUT patientNum INT)
    # Omit ...
DELIMITER ;      # Restore the default separator 

Be careful ：

• If you need to define more than one parameter , Need to use “,” separation

IN： Refers to input parameters

• The value of this parameter must be specified when calling the stored procedure
• This parameter can be used in stored procedures , But it cannot be returned

OUT： Refers to the output parameter

• This parameter can be changed in the stored procedure , And can return

INOUT： Refers to input and output parameters

• The value of this parameter is specified when calling the stored procedure
• Can be changed and returned in stored procedures

Call to execute stored procedure

CALL  Stored procedure name ([ Parameters 1, Parameters 2, …]);

Stored procedure calls are similar to Java Method calls in

call proc_patient_countPatient();

3.5 establish 、 Call stored procedure example

• Use stored procedure query to obtain and output the total number of patients

delimiter //
create procedure proc_patient_countPatient2(out patientCount int)
begin
	select count(0) into patientCount from patient;
end //
delimiter ;

# Call and output the total number of patients 
call proc_patient_countPatient2(@patientCount);
select @patientCount as ' Total number of patients ';

Four 、 Variables in stored procedures

• And Java Language is similar to , Variables can be used when defining stored procedures

DECLARE  Variable name [, Variable name ...]  data type  [DEFAULT  value ];

• Assign values to variables

SET  Variable name  =  Expression value [, Variable name = expression ...] ;

• Declare the transaction time variable trade_time, And set the default value to 2020-07-10

DECLARE trade_time date DEFAULT '2020-07-10';

• Set a variable total The value of is 100

SET total=100;

• matters needing attention ：

When defining a stored procedure , The declaration of all local variables must be placed at the beginning of the stored procedure body ; otherwise , Will prompt grammatical errors

5、 ... and 、MySQL Variable

System variables

• finger MySQL Global variables , With “@@” start , In the form of “@@ Variable name ”

User defined variables

• local variable

  • Commonly used in SQL In the statement block of , Such as ： In a stored procedure BEGIN and END Sentence block
  • The scope is limited to the statement block that defines the variable
  • The life cycle is also limited to the call period of the stored procedure
  • In stored procedures Execute to END when , Local variables will be released

• Session variables

  • It is a variable maintained by the server for each client connection , And MySQL The client is bound
  • Also known as User variables
  • Values can be temporarily stored , And pass it to others in the same connection SQL Statement to use
  • When MySQL When the client connection exits , User variables will be released
  • When creating user variables , General with “@” start , In the form of “@ Variable name ”

MySQL Variable examples

demand ：

• Create stored procedure , Through the department number and patient name entered by the user , Query the last examination time of the patient in the Department

analysis ：

• Input parameters ： Department number and patient name
• Output parameters ： The last examination time of the patient in the Department
• The last examination time of the specified patient in the Department is obtained by dynamic query according to the entered parameter value

Define stored procedures ：

delimiter //
create procedure proc_exam_GetLastExamDateByPatientNameAndDepID
(in patient_name varchar(50), in dep_id int,out last_exam_date datetime)
begin
  declare patient_id int;  # Declare local variables 
	
  select patientid into patient_id from patient 
  where patientname= patient_name;
	
  select patient_id; # Output patient's id
  
  # Use SELECT INTO Statement can assign values to multiple variables at once 
  select max(examdate) into last_exam_date 
  from prescription 
  where patientid = patient_id and depid = dep_id;
end //
delimiter ;

Calling stored procedure ：

# Set user variables @patientName by ' Xia Ying '
set @patientName=' Xia Ying ';
# Set user variables @dep_id by 1 
set @dep_id=1;
# Calling stored procedure 
call proc_exam_GetLastExamDateByPatientNameAndDepID
(@patientName,@dep_id,@last_exam_date);
# Output the last examination time of the patient in a department 
select @last_exam_date;

6、 ... and 、 User variables are passed between stored procedures

User variables can not only be in stored procedures and MySQL Set in the client , You can also pass values between different stored procedures

• Create stored procedure proc1, Set the user variable and assign it “ Wang Ming ”
• Create another stored procedure proc2, Output the assigned user variable information

# The transfer of user variables between two stored procedures 
# Create stored procedure proc1
delimiter //
create procedure `proc1`( )
begin
  set @name = ' Wang Ming ';
end //
delimiter ;

# Create stored procedure proc2
delimiter //
create procedure `proc2`( )
begin
   select concat('name:',@name);
end //
delimiter ;

7、 ... and 、Navicat Created in 、 Calling stored procedure

Navicat Provides a good development environment , Than MySQL Command line operation is more convenient

The basic steps of creating and invoking stored procedures

• Create stored procedure

  • Right click... Under the selected database “ function ” node , Select... From the pop-up drop-down menu “ New function ”
  • In the right area, it will be automatically created Stored procedure template , And write stored procedure code in it

• Run stored procedures

  • Click on “ preservation ” Button , The stored procedure will be automatically saved in the selected database “ function ” Under the node
  • Click on “ function ” Button calls stored procedure
  • According to the definition of stored procedure , Enter the set user parameter value in the pop-up dialog box
  • Click on “ determine ” Button , Execute stored procedures , And output the result

matters needing attention ：

• Stored procedure templates are automatically added DEFINER Assignment statement

• Navicat in , When writing stored procedures, you do not need to use DELIMITER Declare a new delimiter

8、 ... and 、 Set user permission to execute stored procedures

adopt DEFINER and SQL SECURITY Features control the execution permission of stored procedures

grammar ：

CREATE
    [DEFINER = { user | CURRENT_USER }]  # Definition DEFINER, Default to current user 
PROCEDURE  Stored procedure name 
    [SQL SECURITY { DEFINER | INVOKER } | …]# Appoint DEFINER or INVOKER jurisdiction 
BEGIN
    …
END

DEFINER

• Default DEFINER = CURRENT_USER
• Check ‘user_name’@‘host_name’ Authority

INVOKER

• When executing a stored procedure , The caller's permission will be checked

matters needing attention ：

• If omitted sql security characteristic , Then use definer Property specifies the caller , And the caller must have EXECUTE jurisdiction , Must be in mysql.user In the table
• If you will sql security The property is specified as invoker, be definer attribute invalid

Example ：

# For stored procedures p1 Users with execution permission can call it 
create definer = 'admin'@'localhost' procedure p1()
sql security definer
begin
    update t1 set counter = counter + 1;
end;

• ‘admin’@‘localhost’ Users must also have p1 The execution authority of and data table t1 Of UPDATE jurisdiction , To execute the stored procedure ; Otherwise, the execution fails

# Call to execute stored procedure p2 Depends on the caller's permissions 
create definer = 'admin'@'localhost' procedure p2()
sql security invoker
begin
  update t1 set counter = counter + 1;
end;

• If the caller does not have permission to execute the stored procedure or does not have access to the data table t1 Of UPDATE jurisdiction , The stored procedure call fails

Nine 、 Viewing the status of stored procedures

View the stored procedures that have been created in the database

grammar ：

show procedure status;

see hosptal Stored procedures created in the database

# Specify the database name to query the stored procedure 
show procedure status where DB = 'hospital';

# Use LIKE Keyword matches the stored procedure name 
show procedure status like '%patient%';

Ten 、 Look at the creation code of the stored procedure

View the stored procedure code created in the database

SHOW CREATE PROCEDURE  Stored procedure name ;

View stored procedures “proc_patient_countPatient” Create code for

show create procedure proc_patient_countPatient;

11、 ... and 、 Modify stored procedure

Use ALTER PROCEDURE Statement to modify the properties defined when creating a stored procedure

ALTER PROCEDURE  Stored procedure name  [ characteristic ……] ;

Store procedure proc_patient_countPatient Of SQL SECURITY Change the property to INVOKER

alter procedure proc_patient_countPatient
sql security invoker;

Experience

• Use ALTER Keywords can only modify the characteristics of stored procedures , If you want to modify the contents of the procedure body in the stored procedure , You need to delete the stored procedure first , Re create
• stay Navicat in , After modifying the contents of the stored procedure , It can be saved directly

Twelve 、 Delete stored procedure

Use DROP PROCEDURE Statement to delete the created stored procedure

DROP PROCEDURE  Stored procedure name ;

Delete the created stored procedure proc_patient_countPatient

drop procedure if exists;

Be careful ：

• Before creating a stored procedure , have access to IF EXISTS Statement to check whether it already exists , If it doesn't exist , Then create

13、 ... and 、 Control statement of stored procedure

And Java The flow control statements of the language are similar ,MySQL Control statements provided

Conditional statements

1. IF-ELSEIF-ELSE Conditional statements
2. CASE Conditional statements

Loop statement

1. WHILE loop
2. LOOP loop
3. REPEAT loop

Iteration statement

fourteen 、IF-ELSEIF-ELSE Conditional statements

grammar ：

IF  Conditions  THEN  Statement list 
   [ELSEIF  Conditions  THEN  Statement list ]
   [ELSE  Statement list ]
END IF;

Example ：

• According to the patient's family income , Refund medical expenses with different proportions of subsidies
  • Annual household income 5000 If the amount is less than yuan, the total medical expenses of the current year will be refunded 20%
  • Annual household income 10000 The following will be refunded to the total medical expenses of the current year 15%
  • Annual household income 30000 The following will be refunded of the total medical expenses 5%
  • 30000 Those who are more than RMB yuan or not registered will not enjoy the return of medical expenses
  • Enter the patient number and year , Calculate the refundable medical expenses of the patient in the current year

# Example 10： Calculate the returned medical expenses obtained by the patient 
create definer=`root`@`localhost` procedure `proc_income_calSubsidy`
(in i_patientid int ,in i_year varchar(10), out o_subsidy float)
begin
	declare t_totalCost float;
	declare t_income float default -1;
	select sum(checkItemCost) into t_totalCost 
	from prescription p1 
	inner join checkitem on p1.checkItemID = checkitem.checkItemID 
	where patientID = i_patientID 
	and examDate >= concat(i_year,'-01-01') 
	and examDate <= concat(i_year,'-12-31');
	select income into t_income from subsidy 
	where patientID = i_patientID;
# Calculate the return amount according to the rules 
	if t_income >=0 and t_income < 5000 then 
		set o_subsidy = t_totalcost * 0.2;
	elseif t_income >= 5000 and t_income < 10000 then 
		set o_subsidy = t_totalcost * 0.15;
	elseif t_income >= 10000 and t_income < 30000 then 
		set o_subsidy = t_totalcost * 0.05;
	else 
		set o_subsidy = 0;
	end if;
end

15、 ... and 、CASE Conditional statements

grammar 1：

CASE
   WHEN  Conditions  THEN  Statement list 
   [WHEN  Conditions  THEN  Statement list ]
   [ELSE  Statement list ]
END CASE;

grammar 2：

CASE  Name 
   WHEN  Conditional value  THEN  Statement list 
   [WHEN  Conditional value  THEN  Statement list ]
   [ELSE  Statement list ]
END CASE;

Example ：

# Example 11： Use CASE Realize the calculation of the returned medical expenses obtained by patients 
create definer=`root`@`localhost` procedure `proc_income_calsubsidy`
(in i_patientid int ,in i_year varchar(10), out o_subsidy float)
begin
	declare t_totalcost float;
	declare t_income float default -1;
	select sum(checkitemcost) into t_totalcost from prescription p1 
	inner join checkitem on p1.checkitemid = checkitem.checkitemid 
	where patientid = i_patientid 
	and examdate >= concat(i_year,'-01-01') 
	and examdate <= concat(i_year,'-12-31');
	select income into t_income from subsidy 
	where patientid = i_patientid;
# Calculate the return amount according to the rules 
	case 
		when t_income >=0 and t_income < 5000 then set o_subsidy = t_totalcost * 0.2;
		when t_income < 1000 then set o_subsidy = t_totalcost * 0.15;
		when t_income < 30000 then set o_subsidy = t_totalcost * 0.05;
		when t_income >= 30000 or t_income < 0 then set o_subsidy = 0;
	end case;
end

Be careful ： In some cases （ for example , Make an equivalent judgment ）, Using the second way of writing is more concise, but , because CASE There are column names behind , There will be some restrictions on the function

sixteen 、WHILE Loop statement

First, judge whether the condition is true . If set up , Then execute the loop body

[label:] WHILE  Conditions  DO
    Statement list 
END WHILE [label]

• label Label , Used to distinguish between different loops , Omission
  • Use in begin、repeat、while perhaps loop Statement before

Suppose there is a test table test, Yes Id Field 、Val Field

According to the number of lines entered , Batch insert test data

seventeen 、LOOP Loop statement

There is no need to judge the initial conditions , Directly execute the loop body

[label:] LOOP
    Statement list 
END LOOP [label] ;

encounter LEAVE sentence , Exit loop

leave lable

Example ：

• Inspection items , The name of the examination item is gastroscope 、 Enteroscope and bronchofibroscope , Insert in batches 3 The prices of the new items are 70 element

analysis ：

• Save multiple inspection item names with strings , Input parameters as stored procedures
• Check the comma between item names “,” separation

LEAVE Statement leave label The program block identified by the label , Be similar to Java Of break sentence

# Example 13： Batch add inspection items 
create definer=`root`@`localhost` procedure `proc_checkitem_insert`
( in checkitems varchar(100))
begin
 	declare comma_pos int;
     declare current_checkitem varchar(20);
	loop_label: loop
		set comma_pos = locate(',', checkitems);
		set current_checkitem = substr(checkitems, 1, comma_pos-1);
		if current_checkitem <> '' then
			set checkitems = substr(checkitems, comma_pos+1);
    else
      set current_checkitem = checkitems;
    end if;
    insert into checkitem(checkitemname,checkitemcost) values(current_checkitem,70);
		if comma_pos=0 or current_checkitem='' then
      leave loop_label;
    end if;
	end loop loop_label;
end

eighteen 、REPEAT Loop statement

Execute the cycle operation first, and then judge the cycle condition

# And Java Of do-while Loop statements are similar to 
[label:] REPEAT 
    Statement list 
UNTIL  Conditions 
END REPEAT [label]

And LOOP Compare loop statements

• The same thing ： It does not need initial conditions to enter the circulation body directly
• Difference ：REPEAT Statement can set exit conditions

Use REPEAT Loop statement coding implementation

• According to the number of lines entered , To the test table test Insert test data in medium batch

nineteen 、 Iteration statement

Return to the beginning of the block from the current code , Re execution

ITERATE label;

• ITERATE Keywords can be embedded in LOOP、WHILE and REPEAT In the program block

Input the number of data rows to be increased , The randomly generated test data must be greater than 0.5

delimiter //
create definer=`root`@`localhost` procedure `proc_test_insert2`( in rows int)
begin
  	declare rand_val float;
	     loop_label:while rows > 0 do
         select rand() into rand_val;
			if rand_val<0.5 then 
				iterate loop_label;
			end if;
         insert into test values(null, rand_val);
         set rows = rows - 1;
     end while loop_label;
end //
delimiter ;

twenty 、 Summary of this chapter