oracle 批量修改表字段脚本

DECLARE cnt INT;
BEGIN
   select count(1) into cnt from  USER_TAB_COLS  where TABLE_NAME = 'RP_AGTSVRCNT' and COLUMN_NAME  = 'SUMSVRDUR';
   IF (cnt = 0)THEN
        execute immediate 'ALTER TABLE Rp_AgtSvrCnt ADD(SUMSVRDUR INTEGER)';
        cnt :=0;
    end IF;   
    
    select count(1) into cnt from  USER_TAB_COLS  where TABLE_NAME = 'RP_AGTSVRCNT' and COLUMN_NAME  = 'SUMWORKDUR';
    IF (cnt = 0)THEN
        execute immediate 'ALTER TABLE Rp_AgtSvrCnt ADD(SUMWORKDUR INTEGER)';
        cnt :=0;

    end IF; 

END;