In MySQL, the stored procedure cannot realize the problem of migrating and copying the data in the table

A problem description

1.1 Problem Description

Write a stored procedure, the logic is to query the data of some fields in a certain table, and then insert it into another new table.But found in the operation process, the insertion is null.

1. Stored procedure

#select * from tb_studrop PROCEDURE IF EXISTS p_sync_stu;CREATE PROCEDURE p_sync_stu()begin-- Need to define variables that receive cursor datadeclare id int(10);declare u_name varchar(255);declare u_age int(10);declare create_date TIMESTAMP;declare flag int default 0; -- define the flag variable-- Create a cursor to query student information datadeclare stu_data_List cursor for select u_name from tb_stu where create_time>='2022-07-27 10:00:00';-- After the cursor ends, change the mark amount to 1declare exit handler for not found set flag=1;-- open cursoropen stu_data_List;-- loop through the cursorrepeat-- Use the cursor to traverse the result datafetch stu_data_List into u_name;-- save data to tableinsert into tb_stu3 values(u_name);until flag=1end repeat;-- close cursorclose stu_data_List;endcall p_sync_stu();

2. Screenshot

3. After executing the stored procedure, insert data into the table

1.2 Solution

After a lot of investigations, I finally found that when defining the cursor: The field name of declare stu_data_List cursor for select xx and the field name to be declared cannot be the same or the same.

Execute the modified stored procedure again to view the data in the table, as shown in the following figure: You can see that there is already data!