mysql存储过程读书笔记二(controlandconditionallogic)

mysql存储过程读书笔记2(control and conditional logic) 1. If create procedure example3(stu_id int) begin ??? declare stu_name varchar(30); ? ???? select name into stu_name from student where student_id = stu_id; ???? If stu_name is not null

1. If

create procedure example3(stu_id int)
begin
??? declare stu_name varchar(30);
?
???? select name into stu_name from student where student_id = stu_id;
???? If stu_name is not null Then
??????? ?select stu_name;
???? End If;
End;

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2. If ... Else....

create procedure example4(stu_id int)
begin
???? declare stu_name varchar(30);
?
????? select name into stu_name from student where student_id = stu_id;
???? ?If stu_name is not null Then
??????????????? select stu_name;
???????Else
??????????????? ?select 'student is not exist';
???????End If;
End;

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3. IF ... ELSEIF ... ELSE ... END;

drop procedure if exists discounted_price;
create procedure discounted_price(normal_price numeric(8,2), OUT discount_price numeric(8,2))
Begin
??? IF (normal_price) > 500 Then
??????? SET discount_price = normal_price * 0.8;
??? ElseIF (normal_price > 400) Then
??????? SET discount_price = normal_price * 0.9;
????Else
???????? SET discount_price = normal_price;
???? End If;
End

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4. Loop

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drop procedure if exists simple_loop;
create procedure simple_loop()
begin
?DECLARE counter int;
?SET counter = 0;
?
?my_simple_loop: LOOP
??IF counter = 10 Then
???LEAVE my_simple_loop;
??END IF;
??
??SET counter = counter + 1;
?END LOOP my_simple_loop;
?
?select ' now counter is 10';
END