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15 MySQL stored procedures and functions

2022-07-05 23:41:00 【Old vegetable chicken still needs efforts】

15 MySQL- Stored procedures and functions

MySQL from 5. 0 The version began to support stored procedures and functions . Stored procedures and functions can transform complex SQL Logic encapsulated together , Applications don't have to pay attention to the complex problems inside stored procedures and functions SQL Logic , You just need to simply call stored procedures and functions .

1. Overview of stored procedures

1.1 understand

meaning ： save Storage process English is Stored Procedure. Its idea is very simple , It's just a group of people passing through Precompile Of SQL Encapsulation of statements .

Execution process ： Stored procedures are pre stored in MySQL Server , When it needs to be implemented , The client only needs to issue a command to the server to call the stored procedure , The server side can store the pre stored series SQL Execute all statements .

benefits ：

Simplified operation , Improved sql Statement reusability , Reduce the pressure on developers
Reduce errors in operation , Increase of efficiency
Reduce network traffic （ The client does not need to put all SQL The statement is sent to the server through the network ） 4 、 Less SQL The risk of statement exposure to the Internet , It also improves the security of data query

And views 、 Comparison of functions ：

It has the same advantages as view , Clear 、 Security , It can also reduce the amount of network transmission . But it's different from the view , View is Virtual table , Usually do not directly operate on the underlying data table , And stored procedures are programmed SQL, Sure Directly operate the underlying data table , Compared with the collection oriented operation , It can realize some more complex data processing .

Once the stored procedure is created , Using it is as simple as using a function , We can just call the stored procedure name directly . Compared to the function , The stored procedure is no return value Of .

1.2 classification

The parameter type of the stored procedure can be IN、OUT and INOUT. According to this classification is as follows ：

No parameters （ No parameters, no return ）
Just bring IN type （ No return with parameters ）
Just bring OUT type （ No parameters return ）
With both IN And bring OUT（ There are parameters and returns ）
belt INOUT（ There are parameters and returns ）

Be careful ：IN、OUT、INOUT You can take more than one in one stored procedure .

2. Create stored procedure

2.1 Syntax analysis

grammar ：

CREATE PROCEDURE  Stored procedure name (IN|OUT|INOUT  Parameter name   Parameter type ,...)
[characteristics ...]
	BEGIN
		 Stored procedure body 
	END

Be similar to Java The method in ：

 Modifier   Return type   Method name ( Parameter type   Parameter name ,...){
	 Method body ;
}

explain ：

The meaning of the symbol before the parameter
- IN： The current parameter is the input parameter , That is to say, the input parameter ;
  The stored procedure just reads the value of this parameter . If no parameter type is defined , The default is IN, Represents input parameter .
- OUT： The current parameter is the output parameter , That is to say, it shows that ;
  After the execution is complete , The client or application calling the stored procedure can read the value returned by the parameter .
- INOUT： The current parameter can be either an input parameter , It can also be an output parameter .
The formal parameter type can be MySQL Any type in the database .
characteristics Represents the constraint on the stored procedure specified when creating the stored procedure , The value information is as follows ：
```
LANGUAGE SQL
| [NOT] DETERMINISTIC
| { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA }
| SQL SECURITY { DEFINER | INVOKER }
| COMMENT 'string'
```
- LANGUAGE SQL： Note that the stored procedure execution body is composed of SQL The sentences make up , The languages supported by the current system are SQL.
- [NOT] DETERMINISTIC： Indicates whether the result of the stored procedure execution is determined .DETERMINISTIC Indicates that the result is certain . Every time a stored procedure is executed , The same input gets the same output .NOT DETERMINISTIC Indicates that the result is uncertain , The same input may get different outputs . If no value is specified , The default is NOT DETERMINISTIC.
- ```
  { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA }
```
  ： Indicates that the subroutine uses SQL Sentence restrictions .
  - CONTAINS SQL Indicates that the subroutine of the current stored procedure contains SQL sentence , But it doesn't contain read-write data SQL sentence ;
  - NO SQL Indicates that the subroutine of the current stored procedure does not contain any SQL sentence ;
  - READS SQL DATA Indicates that the subroutine of the current stored procedure contains read data SQL sentence ;
  - MODIFIES SQL DATA Indicates that the subroutine of the current stored procedure contains data to be written SQL sentence .
  - By default , The system specifies as CONTAINS SQL.
- ```
  SQL SECURITY { DEFINER | INVOKER }
```
  ： Permission to execute the current stored procedure , That is, it indicates which users can execute the current stored procedure .
  - DEFINER Indicates that only the creator or definer of the current stored procedure can execute the current stored procedure ;
  - INVOKER Indicates that a user with access to the current stored procedure can execute the current stored procedure .
  - If the relevant value is not set , be MySQL The default specified value is DEFINER.
- COMMENT 'string'： Annotation information , Can be used to describe stored procedures .

There can be more than one in the stored procedure body SQL sentence , If only one SQL sentence , You can omit BEGIN and END
Writing stored procedures is not a simple thing , It is possible that the stored procedure requires complex SQL sentence .

1. BEGIN...END：BEGIN...END  There are multiple statements in the middle , Each statement starts with （;） The sign is the Terminator .
2. DECLARE：DECLARE  Used to declare variables , The position of use is  BEGIN...END  In the middle of the sentence , And you need to declare variables before other statements are used .
3. SET： Assignment statement , Used to assign values to variables .
4. SELECT... INTO： Store the query results from the data table into variables , That is, assign values to variables .

You need to set a new end tag
```
DELIMITER  New end tag 
```
because MySQL The default statement end symbol is semicolon ‘;’. To avoid problems with stored procedures SQL Statement terminator conflicts , Need to use DELIMITER Changes the end of a stored procedure .
such as ：“DELIMITER //” The statement will MySQL Is set to //, And “END //” End stored procedure . After the stored procedure is defined, you can use “DELIMITER ;” Restore the default Terminator .DELIMITER You can also specify other symbols as endings .
When using DELIMITER On command , Backslashes should be avoided （‘\’） character , Because the backslash is MySQL The escape character of .
Example ：
```
DELIMITER $

CREATE PROCEDURE  Stored procedure name (IN|OUT|INOUT  Parameter name   Parameter type ,...)
[characteristics ...]
	BEGIN
		sql sentence 1;
		sql sentence 2;

	END $
```

2.2 The code for

give an example 1 ： Create stored procedure select_all_data(), see emps All data of table

DELIMITER $

CREATE PROCEDURE select_all_data()
	BEGIN
		SELECT * FROM emps;
	END $

DELIMITER ;

give an example 2 ： Create stored procedure avg_employee_salary(), Return the average salary of all employees

DELIMITER //

CREATE PROCEDURE avg_employee_salary ()
	BEGIN
		SELECT AVG(salary) AS avg_salary FROM emps;
	END //

DELIMITER ;

give an example 3 ： Create stored procedure show_max_salary(), To view “emps” The highest salary value in the table .

CREATE PROCEDURE show_max_salary()
	LANGUAGE SQL
	NOT DETERMINISTIC
	CONTAINS SQL
	SQL SECURITY DEFINER
	COMMENT ' View maximum salary '
	BEGIN
		SELECT MAX(salary) FROM emps;
	END //
	
DELIMITER ;

give an example 4 ： Create stored procedure show_min_salary(), see “emps” The minimum salary value of the table . And pass the minimum wage OUT Parameters “ms” Output

DELIMITER //

CREATE PROCEDURE show_min_salary(OUT ms DOUBLE)
	BEGIN
		SELECT MIN(salary) INTO ms FROM emps;
	END //

DELIMITER ;

give an example 5 ： Create stored procedure show_someone_salary(), see “emps” The salary of an employee in the table , And use IN Parameters empname Enter employee name .

DELIMITER //

CREATE PROCEDURE show_someone_salary(IN empname VARCHAR( 20 ))
	BEGIN
		SELECT salary FROM emps WHERE ename = empname;
	END //

DELIMITER ;

give an example 6 ： Create stored procedure show_someone_salary2(), see “emps” The salary of an employee in the table , And use IN Parameters empname Enter employee name , use OUT Parameters empsalary Output employee salary .

DELIMITER //

CREATE PROCEDURE show_someone_salary2(IN empname VARCHAR( 20 ),OUT empsalary DOUBLE)
	BEGIN
		SELECT salary INTO empsalary FROM emps WHERE ename = empname;
	END //
	
DELIMITER ;

give an example 7 ： Create stored procedure show_mgr_name(), Query the name of an employee leader , And use INOUT Parameters “empname” Enter employee name , Output the name of the leader .

DELIMITER //

CREATE PROCEDURE show_mgr_name(INOUT empname VARCHAR( 20 ))
	BEGIN
		SELECT ename INTO empname FROM emps
		WHERE eid = (SELECT MID FROM emps WHERE ename=empname);
	END //
	
DELIMITER ;

3. Calling stored procedure

3.1 Invocation format

Stored procedures have a variety of calling methods . Stored procedures must use CALL The statement calls , And the stored procedure is related to the database , If you want to execute stored procedures in other databases , You need to specify a database name , for example CALL dbname.procname.

CALL  Stored procedure name ( Argument list )

Format ：

call in Parameters of the pattern ：
```
CALL sp1(' value ');
```

call out Parameters of the pattern ：

SET @name;
CALL sp1(@name);
SELECT @name;

call inout Parameters of the pattern ：

SET @name= value ;
CALL sp1(@name);
SELECT @name;

3.2 The code for

give an example 1 ：

DELIMITER //

CREATE PROCEDURE CountProc(IN sid INT,OUT num INT)
	BEGIN
		SELECT COUNT(*) INTO num FROM fruits
		WHERE s_id = sid;
	END //
	
DELIMITER ;

Calling stored procedure ：

mysql> CALL CountProc ( 101 , @num);
Query OK, 1 row affected (0.00 sec)

View return results ：

mysql> SELECT @num;

The stored procedure returns the specified s_id=101 The types of fruit offered by our fruit merchants , The return value is stored in num variable , Use SELECT see , The return result is 3 .

give an example 2 ： Create stored procedure , Realize accumulation operation , Calculation 1+2+…+n How much . The specific code is as follows ：

DELIMITER //

CREATE PROCEDURE `add_num`(IN n INT)
	BEGIN
		DECLARE i INT;
		DECLARE sum INT;
		
		SET i = 1 ;
		SET sum = 0 ;
		WHILE i <= n DO
			SET sum = sum + i;
			SET i = i + 1 ;
        END WHILE;
        SELECT sum;
	END //
DELIMITER ;

If you're using a Navicat Tools , So when writing stored procedures ,Navicat It's automatically set DELIMITER For other symbols , We don't need to DELIMITER The operation of .

Use it directly CALL add_num(50); that will do . The parameter I passed in here is 50, That is statistics 1+2+…+50 The sum of accumulation .

3.3 How to debug

stay MySQL in , Stored procedures are not like ordinary programming languages （ such as VC++、Java etc. ） There is a special integrated development environment . therefore , You can go through SELECT sentence , Query the intermediate results of program execution , To debug a SQL Statement correctness . After successful debugging , hold SELECT Move to the next... After the statement SQL After statement , Debug the next SQL sentence . such Step by step , You can complete the debugging of all operations in the stored procedure . Of course , You can also put... In a stored procedure SQL Copy the statement , Separate commissioning section by section .

4. Use of storage function

I learned a lot of functions earlier , Using these functions, you can perform various processing operations on data , Greatly improve the user's management efficiency of the database .MySQL Support for custom functions , Once defined , The calling method is the same as the calling method MySQL Like predefined system functions .

4.1 Syntax analysis

The functions I've learned ：LENGTH、SUBSTR、CONCAT etc.

Grammar format ：

CREATE FUNCTION  Function name ( Parameter name   Parameter type ,...)
RETURNS  return type 
[characteristics ...]
BEGIN
	 The body of the function  # There must be... In the body of the function  RETURN  sentence 
END

explain ：

parameter list ： The specified parameter is IN、OUT or INOUT Only right PROCEDURE It's legal. ,FUNCTION It always defaults to IN Parameters .
RETURNS type Statement represents the type of data returned by the function ;
RETURNS Clause can only be used for FUNCTION Make a designation , For functions, this is mandatory Of . It is used to specify the return type of the function , And the body of the function must contain a RETURN value sentence .
characteristic The constraint on the function specified when creating the function . The value is the same as when creating the stored procedure , No more details here .
The function body can also be used BEGIN…END To express SQL The beginning and end of the code . If the function body has only one statement , You can omit it BEGIN…END.

4.2 Calling the storage function

stay MySQL in , How to use the storage function is the same as MySQL The use of internal functions is the same . In other words , User defined storage functions and MySQL The internal function is a property . The difference lies in , The storage function is User defined Of , And the inner function is MySQL Of Developer definition Of .

SELECT  Function name ( Argument list )

4.3 The code for

give an example 1 ：

Create a storage function , The name is email_by_name(), Parameter definition is null , This function queries Abel Of email, And back to , The data type is string .

DELIMITER //

CREATE FUNCTION email_by_name()
RETURNS VARCHAR( 25 )
DETERMINISTIC
CONTAINS SQL
BEGIN
	RETURN (SELECT email FROM employees WHERE last_name = 'Abel');
END //

DELIMITER ;

call ：

SELECT email_by_name();

give an example 2 ：

Create a storage function , The name is email_by_id(), Parameters of the incoming emp_id, This function queries emp_id Of email, And back to , The data type is string .

DELIMITER //

CREATE FUNCTION email_by_id(emp_id INT)
RETURNS VARCHAR( 25 )
DETERMINISTIC
CONTAINS SQL
BEGIN
	RETURN (SELECT email FROM employees WHERE employee_id = emp_id);
END //

DELIMITER ;

call ：

SET @emp_id = 102 ;
SELECT email_by_id( 102 );

give an example 3 ：

Create a storage function count_by_id(), Parameters of the incoming dept_id, This function queries dept_id Number of employees in the Department , And back to , The data type is integer .

DELIMITER //

CREATE FUNCTION count_by_id(dept_id INT)
RETURNS INT
	LANGUAGE SQL
	NOT DETERMINISTIC
	READS SQL DATA
	SQL SECURITY DEFINER
	COMMENT ' Query the average salary of the Department '
BEGIN
	RETURN (SELECT COUNT(*) FROM employees WHERE department_id = dept_id);
END //

DELIMITER ;

call ：

SET @dept_id = 50 ;
SELECT count_by_id(@dept_id);

Be careful ：

If an error is reported in creating a storage function “you might want to use the less safe log_bin_trust_function_creators variable”, There are two ways to deal with it ：

The way 1 ： Add the necessary functional features “[NOT] DETERMINISTIC” and “{CONTAINS SQL | NO SQL | READS SQL DATA |MODIFIES SQL DATA}”

The way 2 ：

mysql> SET GLOBAL log_bin_trust_function_creators = 1 ;

4.4 Compare stored functions with stored procedures

	keyword	Call syntax	Return value	Application scenarios
stored procedure	PROCEDURE	CALL stored procedure ()	Understanding for 0 One or more	Generally used for updating
Storage function	FUNCTION	SELECT function ()	It can only be one	Generally used when the query result is a value and returned

Besides , Storage functions can be used in query statements , Stored procedures don't work . conversely , Stored procedures are more powerful , Including the ability to perform operations on tables （ For example, create a table , Delete tables, etc ） And transaction operations , These functions are not available in storage functions .

5. View of stored procedures and functions 、 modify 、 Delete

5.1 see

After creation , How do we know the stored procedure we created 、 Is the storage function successful ？

MySQL It stores the state information of stored procedures and functions , Users can use SHOW STATUS Sentence or SHOW CREATE Statement to see , It can also be directly from the... Of the system information_schema Query in database . Here are 3 Methods .

1. Use SHOW CREATE Statement to view the creation information of stored procedures and functions

The basic grammatical structure is as follows ：

SHOW CREATE {PROCEDURE | FUNCTION}  Stored procedure name or function name

give an example ：

SHOW CREATE FUNCTION test_db.CountProc \G

2. Use SHOW STATUS Statement to view the status information of stored procedures and functions

The basic grammatical structure is as follows ：

SHOW {PROCEDURE | FUNCTION} STATUS [LIKE 'pattern']

This statement returns the characteristics of the subroutine , Such as a database 、 name 、 type 、 Creator and date of creation and modification .

[LIKE ‘pattern’]： Matches the name of a stored procedure or function , It can be omitted . When omitted without writing , Will list MySQL Information about all stored procedures or functions that exist in the database . give an example ：SHOW STATUS Statement example , The code is as follows ：

mysql> SHOW PROCEDURE STATUS LIKE 'SELECT%' \G
*************************** 1. row ***************************
Db: test_db
Name: SelectAllData
Type: PROCEDURE
Definer: [email protected]localhost
Modified: 2021 - 10 - 16 15 :55:
Created: 2021 - 10 - 16 15 :55:
Security_type: DEFINER
Comment:
character_set_client: utf8mb
collation_connection: utf8mb4_general_ci
Database Collation: utf8mb4_general_ci
1 row in set (0.00 sec)

3. from information_schema.Routines View the information of stored procedures and functions in the table

MySQL The information of stored procedures and functions is stored in information_schema Database based Routines In the table . You can query the information of stored procedures and functions by querying the records of the table . Its basic grammatical form is as follows ：

SELECT * FROM information_schema.Routines
WHERE ROUTINE_NAME=' The name of a stored procedure or function '[AND ROUTINE_TYPE={'PROCEDURE|FUNCTION'}];

explain ： If in MySQL The stored procedure and function names are the same in the database , It's better to designate ROUTINE_TYPE Query criteria to indicate whether the query is a stored procedure or a function .

give an example ： from Routines The query name in the table is CountProc Information about the storage function of , The code is as follows ：

SELECT * FROM information_schema.Routines
WHERE ROUTINE_NAME='count_by_id' AND ROUTINE_TYPE = 'FUNCTION' \G

5.2 modify

Modify stored procedures or functions , Does not affect stored procedure or function functions , Just modify the relevant features . Use ALTER Statements for .

ALTER {PROCEDURE | FUNCTION}  The name of a stored procedure or function  [characteristic ...]

among ,characteristic Specify the properties of the stored procedure or function , Its value information is the same as that of creating a stored procedure 、 The value information of function is slightly different .

{ CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA }
| SQL SECURITY { DEFINER | INVOKER }
| COMMENT 'string'

CONTAINS SQL, Indicates that the subroutine contains SQL sentence , But does not contain statements that read or write data .
NO SQL, Indicates that the subroutine does not contain SQL sentence .
READS SQL DATA, A statement that contains read data in a subroutine .
MODIFIES SQL DATA, Represents a statement in a subroutine that contains data to be written .
```
  SQL SECURITY { DEFINER | INVOKER }
```
, Indicate who has authority to execute .
- DEFINER, It means that only the definer himself can execute .
- INVOKER, Indicates that the caller can execute .
COMMENT 'string', Represents annotation information .

Modify stored procedures to use ALTER PROCEDURE sentence , Modify the storage function to use ALTER FUNCTION sentence . however , The structure of these two statements is the same , All parameters in the statement are the same .

give an example 1 ：

Modify stored procedure CountProc The definition of . Change the read and write permissions to MODIFIES SQL DATA, And indicate that the caller can execute , The code is as follows ：

ALTER PROCEDURE CountProc
MODIFIES SQL DATA
SQL SECURITY INVOKER ;

Query the modified information ：

SELECT specific_name,sql_data_access,security_type
FROM information_schema.`ROUTINES`
WHERE routine_name = 'CountProc' AND routine_type = 'PROCEDURE';

Results show , The stored procedure was modified successfully . From the results of the query, we can see , Access to data （SQL_DATA_ ACCESS） Has become a MODIFIES SQL DATA, Security type （SECURITY_TYPE） Has become a INVOKER.

give an example 2 ：

Modify storage function CountProc The definition of . Change the read and write permissions to READS SQL DATA, And add the comment information “FIND NAME”, The code is as follows ：

ALTER FUNCTION CountProc
READS SQL DATA
COMMENT 'FIND NAME' ;

Storage function modified successfully . From the results of the query, we can see , Access to data （SQL_DATA_ACCESS） Has become a READS SQL DATA, Function Comments （ROUTINE_COMMENT） Has become a FIND NAME.

5.3 Delete

Deletes stored procedures and functions , have access to DROP sentence , The syntax is as follows ：

DROP {PROCEDURE | FUNCTION} [IF EXISTS]  The name of a stored procedure or function

IF EXISTS： If a program or function does not store , It can prevent errors , Make a use of SHOW WARNINGS View warnings for .

give an example ：

DROP PROCEDURE CountProc;
DROP FUNCTION CountProc;

6. Disputes over the use of stored procedures

Although stored procedures have many advantages , But for the use of stored procedures , There has always been a lot of controversy , For example, some companies require the use of stored procedures for large projects , Some companies explicitly prohibit the use of stored procedures in manuals , Why do these companies have such different requirements for stored procedures ？

6.1 advantage

** Stored procedures can be compiled and used more than once .** Stored procedures are compiled only at creation time , There is no need to recompile later , That's a step up SQL Efficiency of execution .
It can reduce the development workload . Put the code encapsulation Modular , It's actually one of the core ideas of programming , In this way, complex problems can be broken down into different modules , Then the modules can Reuse , While reducing development effort , It also keeps the structure of the code clear .
The security of stored procedure is strong . When setting up stored procedures, we can Set user permissions , This is as secure as the view .
It can reduce the amount of network transmission . Because the code is encapsulated in stored procedures , Each time you use it, you just need to call the stored procedure , This reduces the amount of network traffic .
Good encapsulation . When performing relatively complex database operations , We used to use one by one SQL sentence , Operations that may require multiple database connections to complete , Now it's a stored procedure , It only needs Connect once .

6.2 shortcoming

Based on the above advantages , Many large companies require large projects to use stored procedures , Like Microsoft 、IBM Companies such as . But domestic Alibaba does not recommend developers to use stored procedures , Why is that ？

Ali Development Specification
【 mandatory 】 Stored procedures are not allowed , Stored procedures are difficult to debug and extend , There is no portability .

Although stored procedures have advantages like the above , But the disadvantages are obvious .

Poor portability . Stored procedures cannot be migrated across databases , For example MySQL、Oracle and SQL Server Stored procedures written in , It needs to be rewritten when changing to other databases .
Debugging difficulty . Only a few DBMS Supports debugging of stored procedures . For complex stored procedures , Development and maintenance are not easy . Although there are some third-party tools that can debug stored procedures , But there's a charge .
Version management of stored procedures is difficult . For example, the index of the data table has changed , Can cause stored procedures to fail . We often need version management when we develop software , But the stored procedure itself has no version control , It's troublesome to update the version iteratively .
It is not suitable for high concurrency scenarios . High concurrency scenarios need to reduce the pressure on the database , Sometimes the database will adopt the way of dividing database and table , And it's very scalable , under these circumstances , Stored procedures can become difficult to maintain , Increase the pressure on the database , Obviously not .

Summary ：

Stored procedures are convenient , There are limitations . Although different companies have different attitudes towards stored procedures , But for us developers , No matter what , Mastering stored procedures is one of the necessary skills .

7. Exercise

7.1 Exercise1

-- 5. Exercise
-- ---------------------- ---------------------- ----------------------
-- 5.1 Exercise1
# 0.  preparation 
CREATE DATABASE test15_pro_func;
USE test15_pro_func;
CREATE TABLE admin
(
    id        INT PRIMARY KEY AUTO_INCREMENT,
    user_name VARCHAR(15) NOT NULL,
    pwd       VARCHAR(25) NOT NULL
);

CREATE TABLE beauty
(
    id    INT PRIMARY KEY AUTO_INCREMENT,
    NAME  VARCHAR(15) NOT NULL,
    phone VARCHAR(15) UNIQUE,
    birth DATE
);

INSERT INTO beauty(NAME, phone, birth)
VALUES (' Athena Chu ', '13201233453', '1982-02-12'),
       (' Stefanie Sun ', '13501233653', '1980-12-09'),
       (' Hebe ', '13651238755', '1983-08-21'),
       (' Deng Zi chess ', '17843283452', '1991-11-12'),
       (' Liu Ruoying ', '18635575464', '1989-05-18'),
       (' Mr Yang, the more ', '13761238755', '1994-05-11');
SELECT *
FROM beauty;

# 1.  Create stored procedure insert_user(), Implement the incoming user name and password , Insert into admin In the table 
DELIMITER //
CREATE PROCEDURE insert_user(IN uname varchar(15), IN pwd varchar(25))
BEGIN
    INSERT INTO admin(user_name, pwd)
    VALUES (uname, pwd);
END //
DELIMITER ;

# 2.  Create stored procedure get_phone(), Realize the incoming goddess number , Return the goddess name and goddess phone number 
DELIMITER //
CREATE PROCEDURE get_phone(IN bid int, OUT bname varchar(15), OUT phone varchar(15))
BEGIN
    SELECT NAME, phone
    INTO bname, phone
    FROM beauty
    WHERE id = bid;
END //
DELIMITER ;

CALL get_phone(2, @bname, @phone);
SELECT @bname, @phone;

# 3.  Create stored procedure date_diff(), Realize the introduction of two goddess birthdays , Return date interval size 
DELIMITER //
CREATE PROCEDURE date_diff(IN adate datetime, IN bdate datetime, OUT res int)
BEGIN
    SELECT DATEDIFF(adate, bdate)
    INTO res;
END //
DELIMITER ;

DROP PROCEDURE date_diff;

SET @birth1 = '1992-09-08';
SET @birth2 = '1989-01-03';
CALL date_diff(@birth1, @birth2, @result);
SELECT @result;

# 4.  Create stored procedure format_date(), Pass in a date , Format as xx year xx month xx And return to 
DELIMITER //
CREATE PROCEDURE format_date(IN para datetime, OUT res varchar(30))
BEGIN
    SELECT CONCAT(YEAR(para), ' year ', MONTH(para), ' month ', DAY(para), ' Japan ')
    INTO res;
END //
DELIMITER ;

SET @paraDate = '1992-12-15';
CALL format_date(@paraDate, @res);
SELECT @res;

# 5.  Create stored procedure beauty_limit(), According to the incoming starting index and number of entries , Query the records of the goddess table 
#  Create a inout Stored procedure of mode parameters 
DELIMITER //
CREATE PROCEDURE beauty_limit(IN startIndex int, IN size int)
BEGIN
    SELECT *
    FROM beauty
    LIMIT startIndex , size;
END //
DELIMITER ;

CALL beauty_limit(1, 3);

# 6.  Pass in a and b Two values , Final a and b All double and return 
DELIMITER //
CREATE PROCEDURE add_pro(INOUT a double, INOUT b double)
BEGIN
    SET a = a * 2;
    SET b = b * 2;
END //
DELIMITER ;

SET @a = 5.5;
SET @b = 3.3;
CALL add_pro(@a, @b);
SELECT @a, @b;

# 7.  Delete title 5 Stored procedure 
DROP PROCEDURE IF EXISTS beauty_limit;

# 8.  Check the title 6 Information about stored procedures in 
SHOW CREATE PROCEDURE add_pro;

7.2 Exercise2

-- 5.2 Exercise2
# 0.  preparation 
USE test15_pro_func;
CREATE TABLE employees
AS
SELECT *
FROM study_mysql.employees;
CREATE TABLE departments
AS
SELECT *
FROM study_mysql.departments;

# Return without reference 
# 1.  Create a function get_count(), Number of employees returned to the company 
DELIMITER //
CREATE FUNCTION get_count()
    RETURNS int
    DETERMINISTIC
    CONTAINS SQL
BEGIN
    RETURN (SELECT COUNT(*) FROM employees);
END //
DELIMITER ;

SELECT get_count();

#  You can go back to 
# 2.  Create a function ename_salary(), According to the name of the employee , Return its wages 
DELIMITER //
CREATE FUNCTION ename_salary(ename varchar(20))
    RETURNS double
    DETERMINISTIC
    CONTAINS SQL
BEGIN
    RETURN (SELECT salary
            FROM employees
            WHERE last_name = ename);
END //
DELIMITER ;

SELECT ename_salary('abel');

# 3.  Create a function dept_sal() , According to the Department name , Return the average wage of the Department 
DELIMITER //
CREATE FUNCTION dept_sal(did int)
    RETURNS decimal(10, 2)
    DETERMINISTIC
    CONTAINS SQL
BEGIN
    RETURN (SELECT AVG(salary)
            FROM employees
            GROUP BY department_id
            HAVING department_id = did);
END //
DELIMITER ;

SELECT dept_sal(90);

# 4.  Create a function add_float(), The implementation passes in two float, Return to the sum of the two 
DELIMITER //
CREATE FUNCTION add_float(num1 float, num2 float)
    RETURNS float
    NOT DETERMINISTIC
    NO SQL
BEGIN
    RETURN num1 + num2;
END //
DELIMITER ;

SELECT add_float(2,34);

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