DROP PROCEDURE IF EXISTS proc_add_personnel;
DELIMITER $$
CREATE PROCEDURE proc_add_personnel(ctt INT)
BEGIN
    DECLARE i INT DEFAULT 0;
    DECLARE j INT;
    DECLARE pos VARCHAR(10);
    SET j = FLOOR(1+(RAND()*6);
    
    CASE j WHEN 1 THEN  pos = '美工';
           WHEN 2 THEN  pos = '网页设计';
           WHEN 3 THEN  pos = '软件工程师';
           WHEN 4 THEN  pos = '架构师';
           WHEN 5 THEN  pos = '行政人员';
           ELSE pos = '其他';
    END CASE
    
    WHILE i<ctt DO
     INSERT INTO personnel(`of_year`,`of_position`,`of_wages`) VALUES (FLOOR(1+(RAND()*10)),'',FLOOR(1000+(RAND()*10000)));
     SET i= i+1;
    END WHILE;
END$$

Query : create procedure proc_add_personnel(ctt int) begin  declare i int default 0;  declare j int;  DECLARE pos VARCHAR(10);  set j = ...

Error Code : 1064
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ';
    
    case j when 1 then  pos = '美工';
           WHEN 2 THEN  pos = '网页设?' at line 6

DROP PROCEDURE IF EXISTS proc_add_personnel;
DELIMITER $$
CREATE PROCEDURE proc_add_personnel(ctt INT)
BEGIN
  DECLARE i INT DEFAULT 0;
  DECLARE j INT;
  DECLARE pos VARCHAR(10);
  SET j = FLOOR(1+(RAND()*6));

  CASE j WHEN 1 THEN set pos = '美工' ;
  WHEN 2 THEN set pos = '网页设计';
  WHEN 3 THEN set pos = '软件工程师';
  WHEN 4 THEN set pos = '架构师';
  WHEN 5 THEN set pos = '行政人员';
  ELSE set pos = '其他';
  END CASE;
   
  WHILE i<ctt DO
  INSERT INTO personnel(`of_year`,`of_position`,`of_wages`) VALUES (FLOOR(1+(RAND()*10)),'',FLOOR(1000+(RAND()*10000)));
  SET i= i+1;
  END WHILE;
END$$
DELIMITER ;

------解决方案--------------------
少个分号

------解决方案--------------------
ELIMITER $$
DROP PROCEDURE IF EXISTS proc_add_personnel$$
CREATE PROCEDURE proc_add_personnel(ctt INT)
BEGIN
DECLARE i INT DEFAULT 0;
  DECLARE j INT;
  DECLARE pos VARCHAR(10);
  SET j = FLOOR(1+(RAND()*6));
  CASE j WHEN 1 THEN SET pos='美工';
   WHEN 2 THEN  SET pos = '网页设计';
          WHEN 3 THEN SET pos = '软件工程师';
          WHEN 4 THEN  SET pos = '架构师';
          WHEN 5 THEN SET pos = '行政人员';
          ELSE  SET pos = '其他';
   WHILE i<ctt DO
  INSERT INTO personnel(`of_year`,`of_position`,`of_wages`) VALUES (FLOOR(1+(RAND()*10)),'',FLOOR(1000+(RAND()*10000)));
  SET i= i+1;
  END WHILE;
         
   END CASE;  
      
  
END$$
DELIMITER ;