MySQL stored procedures and triggers

Stored Procedures

First, a simple stored procedure

1, a simple stored procedure

	$$ DELIMITER 
	the Create Procedure Testa () 
	the begin 
	 the Select * from emp; 
	 the Select * from the dept; 
	 End; 
	$$; 
	DELIMITER; 
	- call a stored procedure 
	call testa ();

Structure stored procedure consists of:

1, create a format: create procedure stored procedure name

2, between the begin and end comprising one or more code blocks, a code block using

3, create a need to define in the command line separator delimiter $$

2, the characteristics of the stored procedure

1, to complete the complex calculation and determination

2, programmable strong, flexible

3, SQL programming code may be reused

4, execution speed is relatively fast

5, to reduce the data transmission between the network, to save money

Second, the storage process variables

1, the process variables stored

Requirements: write stored procedures, use variables to take empno = username of 7369

$$ DELIMITER; 
the Create Procedure Testa (); 
the BEGIN 
	the DECLARE my_uname VARCHAR (32) default ""; - defined variables my_uname 
 the SET my_uname = 'Smith'; - variable assignment my_uname 
 - empno = 7369 queries the user name and assign values to my_uname 
 SELECT ename from my_uname INTO EMP WHERE EMPNO = 7369; - assigning a variable 
 select my_uname; - my_uname return value of 
the END; 
$$; 
the Delimiter;

Features:

1, the variable declaration using declare, declare a just declare a variable, the variable must be declared before use.

2, having a variable data types and lengths, consistent with mysql SQL data types, but also to specify a default value, a character set and collation and the like.

3, variables can be assigned through the set, it can be assigned by select into fashion.

4, the variables need to return, you can use the select statement, such as: select the variable name

2, the process variable stored application example

Requirements: tables emp, dept and emp table of the number of rows in the earliest, the latest entry date.

Delimiter $$;
Create procedure stats_emp();
BEGIN
-- 统计emp和dept表中的记录数
 BEGIN
 DECLARE emp_sum int default 0;
 DECLARE dept_sum int default 0;
 select count(*) into emp_sum from emp; 
 select count(*) into dept_sum from dept; 
 select emp_sum,dept_sum;
 END;
-- 统计最早、最晚入职日期
 BEGIN
 DECLARE max_time TIMESTAMP ;
 DECLARE min_time TIMESTAMP;
 select max(hiredate),min(hiredate) into max_time,min_time from emp;
 select max_time,min_time; 
	END;
END
$$;
Delimiter ;

Third, the stored procedure parameters

1, the stored procedure parameters passed IN

Requirements: write stored procedures, incoming empno, returned to the user's ename.

Delimiter $$;
Create procedure test_param(IN my_empno int);
--------
BEGIN
 DECLARE my_ename varchar(32) default '';
 select ename into my_ename from emp where empno=my_empno;
 select my_ename;
END;
$$
Delimiter ;
-- 调用
Call test_param(7369);

prompt:

1, passing parameters: type IN, represents the value of this parameter must be specified when calling a stored procedure, if you do not show designated as IN, then the default is IN type.

2, IN type parameter is generally used for incoming, call a stored procedure is generally not modified and returned.

3, if the need to modify the stored procedure call and return values may be used OUT type parameters.

2, stored procedure parameters outgoing OUT

Requirements: When calling a stored procedure, passing empno, returned to the user's ename.

Delimiter $$;
create procedure test_param(IN my_empno int,OUT my_ename varcahr(32));
--------
BEGIN
 select ename into my_ename from emp where empno=my_empno;
 select my_ename;
END;
$$
Delimiter ;
-- 调用
Set @uname=’’;
Call test_param_out(7369,@uname);

prompt:

1, the outgoing parameters: call a stored procedure, you can change its value, and can be returned.

2, OUT is spread parameters, parameter values can not be used to pass.

3, when calling a stored procedure, OUT parameters also need to specify, but it must be a variable, not a constant.

4. If you need to pass both, at the same time requires outgoing, you can use INOUT type parameters.

3, the variable parameter stored procedure INOUT

Requirements: When calling a stored procedure parameters my_empno and my_ename, both incoming and also outgoing parameters.

Delimiter $$;
create procedure test_param_inout(INOUT my_empno int,INOUT my_ename varchar(32));
BEGIN
 set my_empno=7369;
 set my_ename="smith";
 
 select ename,empno into my_ename,my_empno from emp where empno=my_empno;
END;
$$
Delimiter ;
-- 调用
set @uname:='';
set @empno:=7399;
call test_param_inout(@empno,@uname);
select @empno,@uname;

Features:

1, the variable INOUT variable, the value of the call can be passed, during the call, its value can be modified, but also can return a value.

2, INOUT parameter set function parameters of type IN and OUT

3, when an incoming call is INOUT variable rather than a constant

Fourth, the stored procedure conditional statements

1, conditional statement stored procedure

Requirements: Write a stored procedure, if the user is given empno is even ename, otherwise only return empno.

Delimiter $$;
create procedure test_if(IN my_empno int);
BEGIN
	DECLARE my_ename VARCHAR(32) default ''; 
 if(my_empno %2=0) then 
 select ename into my_ename from emp where empno=my_empno;
	select my_ename;
 else 
 select my_empno;
 end if;
END;
$$
Delimiter ;
-- 调用
call test_if(7369);

Features:

1, the basic structure of conditional statements: if () then ... else ... end if;

2, if the logic determines returns true or false, the expression may be any expression that returns true or false

2, conditional statements stored procedure application example

Requirements: according to the user's incoming empno parameter to determine:

(1) If the user sal is less than 2000, then the user to pay 200

(2) if the user sal less than 1000, to raise the user 500

(3) otherwise pay 100

Delimiter $$;
create procedure test_if_else(IN my_empno int);
BEGIN
	DECLARE my_sal int default 0;
 select sal into my_sal from emp where empno=my_empno;
 if(my_sal<1000) then 
 update emp set sal=sal+500 where empno=my_empno; 
 ELSEIF(my_sal<2000)
 then update emp set sal=sal+200 where empno=my_empno; 
 else update emp set sal=sal+100 where empno=my_empno; 
 end if;
END;
$$
Delimiter ;
-- 调用
call test_if_else(7369);

Features:

Multi-conditional structure:

If()

Then

...

Else if()

Then

...

Else

...

End if;

Fifth, the stored procedure loop

1, while circulation

Demand: Use loop, 10 is inserted into consecutive recording empno emp table.

Delimiter $$;
create procedure test_while();
BEGIN
 DECLARE i int default 0;
 while(i<10) DO
 BEGIN
 set i=i+1;
 insert into acc(id) values(i);
 END;
 END WHILE;
 
END;
$$
Delimiter ;
-- 调用
call test_while();

Features:

1, while the basic sentence structure: while () do begin ... end end while ;;

2, while the logic determines returns true or false, the expression may be any expression that returns true or false

2, repeat loop

Demand: using a repeat loop acc insert 10 consecutive records to the table id

Delimiter $$;
create procedure test_repeat();
BEGIN
 DECLARE i int default 100;
 REPEAT
 BEGIN
 set i=i+1;
 insert into acc(id) values(i);
 END;
 UNTIL i>=110
 END REPEAT;
END;
$$
Delimiter ;
-- 调用
call test_repeat();

Features:

1, repeat the basic sentence structure: repeat begin ... end until end repeat ;;

2, while the logic determines returns true or false, the expression may be any expression that returns true or false

Sixth, the stored procedure using a cursor

1. What are cursors

Requirements: write stored procedures, use the cursor, the uid is an even number of records one by one to update the user name.

$$ DELIMITER; 
Create Procedure test_cursor (); 
the BEGIN 
 DECLARE the INT StopFlag the DEFAULT 0; - cursor stop flag 0: No Stop 1: Stopped 
 DECLARE my_uname VARCHAR (32) default ' '; - a user name stored query 
 DECLARE uname_cursor cURSOR for select uname from acc where uid% 2 = 0; - defining a cursor uname_cursor, and specify the result set 
 DECLARE CONTINUE HANDLER for NOT found set stopflag = 1; - after the cursor is set to StopFlag. 1 
	 open uname_cursor; - open cursor 
 FETCH uname_cursor into my_uname; - - cursor step forward, taken in a record into my_uname my_uname 
 the WHILE (StopFlag = 0) 
 the DO 
 the BEGIN 
 Update the uname ACC SET = CONCAT (my_uname, "CUR _") WHERE the uname = my_uname; 
 uname_cursor INTO my_uname the FETCH; 
 the END; 
 End the WHILE; 
 Close uname_cursor; 
the END;
$$ 
the Delimiter; 
- call 
call test_repeat ();

Features:

declare uname_cur Cursor for select uname from acc where uid%2=0;

1, the cursor is to save the query results temporary memory area

2, uname_cur cursor variable holds the provisional results of the query, the query result set is actually

Declare continue handler for not found set stopflag=1;

3, when the cursor variable holds the query results are again (traverse), reaches the end, the variable stopflag to 1.

4, FETCH uname_cursor into my_uname; - cursor step forward, taken in a record into my_uname

Mysql function

A, a simple function

Demand: Write function, passing a uid, returns the user's uname

Delimiter $$;
 CREATE FUNCTION f01_simple(my_uid int) RETURNS varchar(32) CHARSET utf8
	BEGIN
 DECLARE my_uname varchar(32) default '';
 select uname into my_uname from acc where uid=my_uid;
	RETURN my_uname;
END
$$
Delimiter ;
-- 调用
Select f01_simple(2);

Features:

1, create a function using the create function function name (parameter) return return value

2, the function is placed between the begin and end member

3, return specified function return value

4, function calls: select function name (arguments);

Second, the custom function integrated application examples

1, exemplary custom function 01

Demand: Enter the user UID, uuid value obtained accountid, uid, uname combination, as the user's unique identification.

Delimiter $$;
 CREATE FUNCTION test_uuid(my_uid int) RETURNS varchar(32) CHARSET utf8
BEGIN
 DECLARE uuid varchar(32) default '';
 select CONCAT(accountid,"_",uid,"_",uname) INTO uuid from acc where uid=my_uid;
 RETURN uuid;
END
$$;
Delimiter ;
-- 调用
Select test_uuid(2);

2, exemplary custom function 02

Requirements: Enter the user uid, uid to calculate the total price for all orders under where the accounts.

Trigger trigger

Scene: In general for auditing, business data integrity

1, what is the trigger

Demand: in auditing purposes, when someone inserts a record into table users, the insertion uid, uname operation and the operation time and recorded.

$$ DELIMITER; 
the CREATE TRIGGER `` tr_users_insert` an AFTER the INSERT the ON users` 
the FOR EACH the ROW 
	the BEGIN 
- New inserted after the current user information 
 insert into oplog (uid, uname, action, optime) VALUES (NEW.uid, NEW.uname, 'INSERT', now ()); 
the END; 
$$; 
the Delimiter;

Features:

1, create triggers using create trigger trigger name.

2, when the trigger? after insert on users, as well as after treatment before, is after (before) or (after) the table before the operation trigger action pair.

3, the operation of what event triggers? After insert on users, the operation time including insert, update, delete

4, triggering what table? after insert on users

5, the impact of scope? For each row

Trigger: with functions, stored procedures, as trigger is an object that can operate according to the event on the table, triggering a number of actions that can be insert, update, delete and other modification operations.

2, production examples of the flip-flop

Requirements: in auditing purposes, when users delete the table, record the main field value of the record before deleting.

Delimiter $$;
CREATE TRIGGER `tr_user_delete` BEFORE DELETE ON `users` FOR EACH ROW begin 
-- OLD对字段表更新前的数据 
 insert into oplog(uid,uname,action,optime,old_value) values(OLD.uid,OLD.uname,"delete",now(),OLD.regtime);
END;
$$;
Delimiter ;