多表联合查询语句

select
		dpt.*,
		info.*,
		gd.*,
		mat.*
		from depart as dpt
		left join info_sys as info on dpt.id = info.dept_name
		left join grade as gd on info.id = gd.grade
		left join material as mat on gd.id = mat.material_pro
		where dpt.id = #{id}
		or info.id = #{id}
		or gd.id = #{id}
		or mat.id = #{id}

		<if test="offset != null and limit != null">
			limit ${offset}, ${limit}
		</if>

附表的外键是主表的主键

将主表的主键的id放在前，将附表的外键放在后

中间用等号链接起来

最后边加上where条件语句

后边加上if语句