新增
让st_student中得id,st_name等于xs_student表得xh,xm
INSERT INTO
st_student (id,st_name)
SELECT
xh,xm
FROM
xs_student
WHERE
NOT EXISTS (
SELECT
*
FROM
st_student
WHERE
st_student.id = xs_student.xh
);
//2019 更新成 2019级
update st_student set field_two=CONCAT(field_two,'级')
更新年级
UPDATE st_student,sys_dict_item
SET field_two = item_value
WHERE
st_student.field_two = sys_dict_item.item_text