mysql触发器怎么写 [英] how to write mysql trigger

问题描述

有两个表
表A

there are two tables
table A

如果用户使用此查询插入A值(abc，1,50);"

if user use this query "insert into A values(abc,1,50);"

然后，触发器应检查表B"中的"student_name"，如果表B"中已存在"student_name"，则 更新表B中的"all_marks"字段，例如"all_marks"应为60

then trigger should check student_name in "Table B" if student_name is already there in "table B" then update "all_marks"field in table B eg., "all_marks" should be 60

如果表B"中没有"student_name""abc"，则应将相同的"student_name"，"student_class"，"student_marks"插入表B

if student_name "abc" is not there in "table B" then same student_name ,student_class, student_marks should be inserted into table B

delimiter $$
create trigger insert_into_summary 
    after insert on A 
    for each row 
begin
     if
//** here i want to write the if condition **  
     insert into B (name,class,overall_marks)
     values(new.name,new.class,new.marks,);
     else 
     update B set all_marks=old.all_marks+new.student_marks;
end $$
delimiter ;

请帮助我编写触发器.

推荐答案

您可以使用

You can simply this by using On Duplicate Key Update . Add a unique key on student name / ID then use the following code in your trigger

begin
   insert into summary_score (name,number,all_marks)
   values(new.name,new.marks,new.score)
   on duplicate key update all_marks=old.all_marks+new.student_marks
  where B.Name=new.Name;
end $$

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