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MySQL 存储过程经常使用语法

發布時間：2023/12/13 综合教程 22 生活家

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MySQL 存儲過程是從 MySQL 5.0 開始添加的新功能。存儲過程的長處有一籮筐。只是最基本的還是運行效率和SQL 代碼封裝。特別是 SQL 代碼封裝功能，假設沒有存儲過程，在外部程序訪問數據庫時（比如 PHP），要組織非常多 SQL 語句。特別是業務邏輯復雜的時候，一大堆的 SQL 和條件夾雜在 PHP 代碼中，讓人不寒而栗。如今有了 MySQL 存儲過程，業務邏輯能夠封裝存儲過程中，這樣不僅easy維護，并且運行效率也高。
一、MySQL 創建存儲過程
“pr_add” 是個簡單的 MySQL 存儲過程，這個存儲過程有兩個 int 類型的輸入參數 “a”、“b”，返回這兩個參數的和。
drop procedure if exists pr_add;
-- 計算兩個數之和
create procedure pr_add
(
a int,
b int
)
begin
declare c int;
if a is null then
set a = 0;
end if;
if b is null then
set b = 0;
end if;
set c = a + b;
select c as sum;
/*
return c;- 不能在 MySQL 存儲過程中使用。return 僅僅能出如今函數中。
/
end;
二、調用 MySQL 存儲過程
call pr_add(10, 20);
運行 MySQL 存儲過程，存儲過程參數為 MySQL 用戶變量。
set @a = 10;
set @b = 20;
call pr_add(@a, @b);
三、MySQL 存儲過程特點
創建 MySQL 存儲過程的簡單語法為：
create procedure 存儲過程名字()
(
[in|out|inout] 參數 datatype
)
begin
MySQL 語句;
end;
MySQL 存儲過程參數假設不顯式指定“in”、“out”、“inout”，則默覺得“in”。習慣上，對于是“in” 的參數，我們都不會顯式指定。
1. MySQL 存儲過程名字后面的“()”是必須的，即使沒有一個參數，也須要“()”
2. MySQL 存儲過程參數，不能在參數名稱前加“@”，如：“@a int”。以下的創建存儲過程語法在 MySQL 中是錯誤的（在 SQL Server 中是正確的）。 MySQL 存儲過程中的變量，不須要在變量名字前加“@”，盡管 MySQL client用戶變量要加個“@”。
create procedure pr_add
(
@a int,- 錯誤
b int - 正確
)
3. MySQL 存儲過程的參數不能指定默認值。
4. MySQL 存儲過程不須要在 procedure body 前面加 “as”。而 SQL Server 存儲過程必須加 “as” keyword。
create procedure pr_add
(
a int,
b int
)
as - 錯誤，MySQL 不須要 “as”
begin
mysql statement ...;
end;
5. 假設 MySQL 存儲過程中包括多條 MySQL 語句，則須要 begin end keyword。
create procedure pr_add
(
a int,
b int
)
begin
mysql statement 1 ...;
mysql statement 2 ...;
end;
6. MySQL 存儲過程中的每條語句的末尾，都要加上分號 “;”
...
declare c int;
if a is null then
set a = 0;
end if;
...
end;
7. MySQL 存儲過程中的凝視。
/*
這是個
多行 MySQL 凝視。
/
declare c int; - 這是單行 MySQL 凝視（注意- 后至少要有一個空格）
if a is null then 這也是個單行 MySQL 凝視
set a = 0;
end if;
...
end;
8. 不能在 MySQL 存儲過程中使用 “return” keyword。
set c = a + b;
select c as sum;
/*
return c;- 不能在 MySQL 存儲過程中使用。return 僅僅能出如今函數中。
/
end;
9. 調用 MySQL 存儲過程時候，須要在過程名字后面加“()”，即使沒有一個參數，也須要“()”
call pr_no_param();
10. 由于 MySQL 存儲過程參數沒有默認值，所以在調用 MySQL 存儲過程時候，不能省略參數。能夠用 null 來替代。
call pr_add(10, null);

1，前提
須要MySQL 5

2，Hello World
MySQL存儲過程之Hello World

Java代碼

DELIMITER$$

DROPPROCEDUREIFEXISTSHelloWorld$$
CREATEPROCEDUREHelloWorld()
BEGIN
SELECT"HelloWorld!";
END$$

DELIMITER;

DELIMITER $$

DROP PROCEDURE IF EXISTS HelloWorld$$
CREATE PROCEDURE HelloWorld()
BEGIN
    SELECT "Hello World!";
END$$

DELIMITER ;

3，變量
使用DECLARE來聲明，DEFAULT賦默認值，SET賦值

Java代碼

DECLAREcounterINTDEFAULT0;
SETcounter=counter+1;

DECLARE counter INT DEFAULT 0;
SET counter = counter+1;

4，參數
IN為默認類型，值必須在調用時指定，值不能返回（值傳遞）
OUT值能夠返回（指針傳遞）
INOUT值必須在調用時指定，值能夠返回

Java代碼

CREATEPROCEDUREtest(aINT,OUTbFLOAT,INOUTcINT)

CREATE PROCEDURE test(a INT, OUT b FLOAT, INOUT c INT)

5，條件推斷
IF THEN、ELSEIF、ELSE、END IF

Java代碼

DELIMITER$$

DROPPROCEDUREIFEXISTSdiscounted_price$$
CREATEPROCEDUREdiscunted_price(normal_priceNUMERIC(8,2),OUTdiscount_priceNUMERIC(8,2))
BEGIN
IF(normal_price>500)THEN
SETdiscount_price=normal_price*.8;
ELSEIF(normal_price>100)THEN
SETdiscount_price=normal_price*.9;
ELSE
SETdiscount_price=normal_price;
ENDIF;
END$$

DELIMITER;

DELIMITER $$

DROP PROCEDURE IF EXISTS discounted_price$$
CREATE PROCEDURE discunted_price(normal_price NUMERIC(8, 2), OUT discount_price NUMERIC(8, 2))
BEGIN
    IF (normal_price > 500) THEN
        SET discount_price = normal_price * .8;
    ELSEIF (normal_price > 100) THEN
        SET discount_price = normal_price * .9;
    ELSE
        SET discount_price = normal_price;
    END IF;
END$$

DELIMITER ;

6，循環
LOOP、END LOOP

Java代碼

DELIMITER$$

DROPPROCEDUREIFEXISTSsimple_loop$$

CREATEPROCEDUREsimple_loop(OUTcounterINT)
BEGIN
SETcounter=0;
my_simple_loop:LOOP
SETcounter=counter+1;
IFcounter=10THEN
LEAVEmy_simple_loop;
ENDIF;
ENDLOOPmy_simple_loop;
END$$

DELIMITER;

DELIMITER $$

DROP PROCEDURE IF EXISTS simple_loop$$

CREATE PROCEDURE simple_loop(OUT counter INT)
BEGIN
    SET counter = 0;
    my_simple_loop: LOOP
        SET counter = counter+1;
        IF counter = 10 THEN
            LEAVE my_simple_loop;
        END IF;
    END LOOP my_simple_loop;
END$$

DELIMITER ;

WHILE DO、END WHILE

Java代碼

DELIMITER$$

DROPPROCEDUREIFEXISTSsimple_while$$

CREATEPROCEDUREsimple_while(OUTcounterINT)
BEGIN
SETcounter=0;
WHILEcounter!=10DO
SETcounter=counter+1;
ENDWHILE;
END$$

DELIMITER;

DELIMITER $$

DROP PROCEDURE IF EXISTS simple_while$$

CREATE PROCEDURE simple_while(OUT counter INT)
BEGIN
    SET counter = 0;
    WHILE counter != 10 DO
        SET counter = counter+1;
    END WHILE;
END$$

DELIMITER ;

REPEAT、UNTILL

Java代碼

DELIMITER$$

DROPPROCEDUREIFEXISTSsimple_repeat$$

CREATEPROCEDUREsimple_repeat(OUTcounterINT)
BEGIN
SETcounter=0;
REPEAT
SETcounter=counter+1;
UNTILcounter=10ENDREPEAT;
END$$

DELIMITER;

DELIMITER $$

DROP PROCEDURE IF EXISTS simple_repeat$$

CREATE PROCEDURE simple_repeat(OUT counter INT)
BEGIN
    SET counter = 0;
    REPEAT
        SET counter = counter+1;
    UNTIL counter = 10 END REPEAT;
END$$

DELIMITER ;

7，異常處理
假設用cursor獲取SELECT語句返回的全部結果集時應該定義NOT FOUND error handler來防止存儲程序提前終結
假設SQL語句可能返回constraint violation等錯誤時應該創建一個handler來防止程序終結

8，數據庫交互
INTO用于存儲單行記錄的查詢結果

Java代碼

DECLAREtotal_salesNUMERIC(8,2);
SELECTSUM(sale_value)INTOtotal_salesFROMsalesWHEREcustomer_id=in_customer_id;

DECLARE total_sales NUMERIC(8, 2);
SELECT SUM(sale_value) INTO total_sales FROM sales WHERE customer_id=in_customer_id;

CURSOR用于處理多行記錄的查詢結果

Java代碼

DELIMITER$$

DROPPROCEDUREIFEXITScursor_example$$
CREATEPROCEDUREcursor_example()
READSSQLDATA
BEGIN
DECLAREl_employee_idINT;
DECLAREl_salaryNUMERIC(8,2);
DECLAREl_department_idINT;
DECLAREdoneINTDEFAULT0;
DECLAREcur1CURSORFORSELECTemployee_id,salary,department_idFROMemployees;
DECLARECONTINUEHANDLERFORNOTFOUNDSETdone=1;

OPENcur1;
emp_loop:LOOP
FETCHcur1INTOl_employee_id,l_salary,l_department_id;
IFdone=1THEN
LEAVEemp_loop;
ENDIF;
ENDLOOPemp_loop;
CLOSEcur1;
END$$
DELIMITER;

DELIMITER $$

DROP PROCEDURE IF EXITS cursor_example$$
CREATE PROCEDURE cursor_example()
    READS SQL DATA
BEGIN
    DECLARE l_employee_id INT;
    DECLARE l_salary NUMERIC(8,2);
    DECLARE l_department_id INT;
    DECLARE done INT DEFAULT 0;
    DECLARE cur1 CURSOR FOR SELECT employee_id, salary, department_id FROM employees;
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done=1;

    OPEN cur1;
    emp_loop: LOOP
        FETCH cur1 INTO l_employee_id, l_salary, l_department_id;
        IF done=1 THEN
            LEAVE emp_loop;
        END IF;
    END LOOP emp_loop;
    CLOSE cur1;
END$$
DELIMITER ;

unbounded SELECT語句用于存儲過程返回結果集

Java代碼

DELIMITER$$
DROPPROCEDUREIFEXISTSsp_emps_in_dept$$
CREATEPROCEDUREsp_emps_in_dept(in_employee_idINT)
BEGIN
SELECTemployee_id,surname,firstname,address1,address2,zipcode,date_of_birthFROMemployeesWHEREdepartment_id=in_employee_id;
END$$

DELIMITER;

DELIMITER $$
DROP PROCEDURE IF EXISTS sp_emps_in_dept$$
CREATE PROCEDURE sp_emps_in_dept(in_employee_id INT)
BEGIN
    SELECT employee_id, surname, firstname, address1, address2, zipcode, date_of_birth FROM employees WHERE department_id=in_employee_id;
END$$

DELIMITER ;

UPDATE、INSERT、DELETE、CREATE TABLE等非查詢語句也能夠嵌入存儲過程里

Java代碼

DELIMITER$$

DROPPROCEDUREIFEXITSsp_update_salary$$
CREATEPROCEDUREsp_update_salary(in_employee_idINT,in_new_salaryNUMERIC(8,2))
BEGIN
IFin_new_salary<5000ORin_new_salary>500000THEN
SELECT"Illegalsalary:salarymustbebetween$5000and$500,000";
ELSE
UPDATEemployeesSETsalary=in_new_salaryWHEREemployee_id=in_employee_id;
ENDIF:
END$$

DELIMITER;

DELIMITER $$

DROP PROCEDURE IF EXITS sp_update_salary$$
CREATE PROCEDURE sp_update_salary(in_employee_id INT, in_new_salary NUMERIC(8,2))
BEGIN
    IF in_new_salary < 5000 OR in_new_salary > 500000 THEN
        SELECT "Illegal salary: salary must be between $5000 and $500, 000";
    ELSE
        UPDATE employees SET salary=in_new_salary WHERE employee_id=in_employee_id;
    END IF:
END$$

DELIMITER ;

9，使用CALL調用存儲程序

Java代碼

DELIMITER$$

DROPPROCEDUREIFEXISTScall_example$$
CREATEPROCEDUREcall_example(employee_idINT,employee_typeVARCHAR(20))
NOSQL
BEGIN
DECLAREl_bonus_amountNUMERIC(8,2);

IFemployee_type='MANAGER'THEN
CALLcalc_manager_bonus(employee_id,l_bonus_amount);
ELSE
CALLcalc_minion_bonus(employee_id,l_bonus_amount);
ENDIF;
CALLgrant_bonus(employee_id,l_bonus_amount);
END$$
DELIMITER;

DELIMITER $$

DROP PROCEDURE IF EXISTS call_example$$
CREATE PROCEDURE call_example(employee_id INT, employee_type VARCHAR(20))
    NO SQL
BEGIN
    DECLARE l_bonus_amount NUMERIC(8,2);

    IF employee_type='MANAGER' THEN
        CALL calc_manager_bonus(employee_id, l_bonus_amount);
    ELSE
        CALL calc_minion_bonus(employee_id, l_bonus_amount);
    END IF;
    CALL grant_bonus(employee_id, l_bonus_amount);
END$$
DELIMITER ;

10，一個復雜的樣例

Java代碼

CREATEPROCEDUREputting_it_all_together(in_department_idINT)
MODIFIESSQLDATA
BEGIN
DECLAREl_employee_idINT;
DECLAREl_salaryNUMERIC(8,2);
DECLAREl_department_idINT;
DECLAREl_new_salaryNUMERIC(8,2);
DECLAREdoneINTDEFAULT0;

DECLAREcur1CURSORFOR
SELECTemployee_id,salary,department_id
FROMemployees
WHEREdepartment_id=in_department_id;

DECLARECONTINUEHANDLERFORNOTFOUNDSETdone=1;

CREATETEMPORARYTABLEIFNOTEXISTSemp_raises
(employee_idINT,department_idINT,new_salaryNUMERIC(8,2));

OPENcur1;
emp_loop:LOOP
FETCHcur1INTOl_employee_id,l_salary,l_department_id;
IFdone=1THEN/*Nomorerows*/
LEAVEemp_loop;
ENDIF;
CALLnew_salary(1_employee_id,l_new_salary);/*Getnewsalary*/
IF(l_new_salary<>l_salary)THEN/*Salarychanged*/
UPDATEemployees
SETsalary=l_new_salary
WHEREemployee_id=l_employee_id;
/*Keeptrackofchangedsalaries*/
INSERTINTOemp_raises(employee_id,department_id,new_salary)
VALUES(l_employee_id,l_department_id,l_new_salary);
ENDIF:
ENDLOOPemp_loop;
CLOSEcur1;
/*Printoutthechangedsalaries*/
SELECTemployee_id,department_id,new_salaryfromemp_raises
ORDERBYemployee_id;
END;

CREATE PROCEDURE putting_it_all_together(in_department_id INT)
    MODIFIES SQL DATA
BEGIN
    DECLARE l_employee_id INT;
    DECLARE l_salary NUMERIC(8,2);
    DECLARE l_department_id INT;
    DECLARE l_new_salary NUMERIC(8,2);
    DECLARE done INT DEFAULT 0;

    DECLARE cur1 CURSOR FOR
        SELECT employee_id, salary, department_id
        FROM employees
        WHERE department_id=in_department_id;

    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done=1;

    CREATE TEMPORARY TABLE IF NOT EXISTS emp_raises
        (employee_id INT, department_id INT, new_salary NUMERIC(8,2));

    OPEN cur1;
    emp_loop: LOOP
        FETCH cur1 INTO l_employee_id, l_salary, l_department_id;
        IF done=1 THEN    /* No more rows */
            LEAVE emp_loop;
        END IF;
        CALL new_salary(1_employee_id, l_new_salary); /* Get new salary */
        IF (l_new_salary <> l_salary) THEN  /* Salary changed */
            UPDATE employees
                SET salary=l_new_salary
            WHERE employee_id=l_employee_id;
            /* Keep track of changed salaries */
            INSERT INTO emp_raises(employee_id, department_id, new_salary)
                VALUES (l_employee_id, l_department_id, l_new_salary);
        END IF:
    END LOOP emp_loop;
    CLOSE cur1;
    /* Print out the changed salaries */
    SELECT employee_id, department_id, new_salary from emp_raises
        ORDER BY employee_id;
END;

11，存儲方法
存儲方法與存儲過程的差別
1，存儲方法的參數列表僅僅同意IN類型的參數，并且不是必需也不同意指定INkeyword
2，存儲方法返回一個單一的值，值的類型在存儲方法的頭部定義
3，存儲方法能夠在SQL語句內部調用
4，存儲方法不能返回結果集
語法：

Java代碼

CREATE
[DEFINER={user|CURRENT_USER}]
PROCEDUREsp_name([proc_parameter[,...]])
[characteristic...]routine_body

CREATE
[DEFINER={user|CURRENT_USER}]
FUNCTIONsp_name([func_parameter[,...]])
RETURNStype
[characteristic...]routine_body

proc_parameter:
[IN|OUT|INOUT]param_nametype

func_parameter:
param_nametype

type:
AnyvalidMySQLdatatype

characteristic:
LANGUAGESQL
|[NOT]DETERMINISTIC
|{CONTAINSSQL|NOSQL|READSSQLDATA|MODIFIESSQLDATA}
|SQLSECURITY{DEFINER|INVOKER}
|COMMENT'string'

routine_body:
ValidSQLprocedurestatement

CREATE
    [DEFINER = { user | CURRENT_USER }]
    PROCEDURE sp_name ([proc_parameter[,...]])
    [characteristic ...] routine_body

CREATE
    [DEFINER = { user | CURRENT_USER }]
    FUNCTION sp_name ([func_parameter[,...]])
    RETURNS type
    [characteristic ...] routine_body
    
proc_parameter:
    [ IN | OUT | INOUT ] param_name type
    
func_parameter:
    param_name type

type:
    Any valid MySQL data type

characteristic:
    LANGUAGE SQL
  | [NOT] DETERMINISTIC
  | { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA }
  | SQL SECURITY { DEFINER | INVOKER }
  | COMMENT 'string'

routine_body:
    Valid SQL procedure statement

各參數說明見CREATE PROCEDURE and CREATE FUNCTION Syntax
樣例：

Java代碼

DELIMITER$$

DROPFUNCTIONIFEXISTSf_discount_price$$
CREATEFUNCTIONf_discount_price
(normal_priceNUMERIC(8,2))
RETURNSNUMERIC(8,2)
DETERMINISTIC
BEGIN
DECLAREdiscount_priceNUMERIC(8,2);

IF(normal_price>500)THEN
SETdiscount_price=normal_price*.8;
ELSEIF(normal_price>100)THEN
SETdiscount_price=normal_price*.9;
ELSE
SETdiscount_price=normal_price;
ENDIF;

RETURN(discount_price);
END$$

DELIMITER;

DELIMITER $$

DROP FUNCTION IF EXISTS f_discount_price$$
CREATE FUNCTION f_discount_price
    (normal_price NUMERIC(8,2))
    RETURNS NUMERIC(8,2)
    DETERMINISTIC
BEGIN
    DECLARE discount_price NUMERIC(8,2);

    IF (normal_price > 500) THEN
        SET discount_price = normal_price * .8;
    ELSEIF (normal_price >100) THEN
        SET discount_price = normal_price * .9;
    ELSE
        SET discount_price = normal_price;
    END IF;

    RETURN(discount_price);
END$$

DELIMITER ;

12，觸發器
觸發器在INSERT、UPDATE或DELETE等DML語句改動數據庫表時觸發
觸發器的典型應用場景是重要的業務邏輯、提高性能、監控表的改動等
觸發器能夠在DML語句運行前或后觸發

Java代碼

DELIMITER$$

DROPTRIGGERsales_trigger$$
CREATETRIGGERsales_trigger
BEFOREINSERTONsales
FOREACHROW
BEGIN
IFNEW.sale_value>500THEN
SETNEW.free_shipping='Y';
ELSE
SETNEW.free_shipping='N';
ENDIF;

IFNEW.sale_value>1000THEN
SETNEW.discount=NEW.sale_value*.15;
ELSE
SETNEW.discount=0;
ENDIF;
END$$

DELIMITER;

轉自：http://fyb613.blog.163.com/blog/static/325460922010044417672/

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MySQL 存储过程 经常使用语法

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MySQL 存储过程经常使用语法