MyBatis limit分页 MyBatis limit分页设置的实现
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错误的写法:
<select id="queryMyApplicationRecord" parameterType="MyApplicationRequest" resultMap="myApplicationMap"> SELECT a.*, FROM tb_user a WHERE 1=1 <if test="ids != null and ids.size()!=0"> AND a.id IN <foreach collection="ids" item="id" index="index" open="(" close=")" separator=","> #{id} </foreach> </if> <if test="statusList != null and statusList.size()!=0"> AND a.status IN <foreach collection="statusList" item="status" index="index" open="(" close=")" separator=","> #{status} </foreach> </if> ORDER BY a.create_time desc LIMIT (#{pageNo}-1)*#{pageSize},#{pageSize}; // 错误 </select>
在MyBatis中LIMIT之后的语句不允许的变量不允许进行算数运算,会报错。
正确的写法一:
<select id="queryMyApplicationRecord" parameterType="MyApplicationRequest" resultMap="myApplicationMap"> SELECT a.*, FROM tb_user a WHERE 1=1 <if test="ids != null and ids.size()!=0"> AND a.id IN <foreach collection="ids" item="id" index="index" open="(" close=")" separator=","> #{id} </foreach> </if> <if test="statusList != null and statusList.size()!=0"> AND a.status IN <foreach collection="statusList" item="status" index="index" open="(" close=")" separator=","> #{status} </foreach> </if> ORDER BY a.create_time desc LIMIT ${(pageNo-1)*pageSize},${pageSize}; (正确) </select>
正确的写法二:(推荐)
<select id="queryMyApplicationRecord" parameterType="MyApplicationRequest" resultMap="myApplicationMap"> SELECT a.*, FROM tb_user a WHERE 1=1 <if test="ids != null and ids.size()!=0"> AND a.id IN <foreach collection="ids" item="id" index="index" open="(" close=")" separator=","> #{id} </foreach> </if> <if test="statusList != null and statusList.size()!=0"> AND a.status IN <foreach collection="statusList" item="status" index="index" open="(" close=")" separator=","> #{status} </foreach> </if> ORDER BY a.create_time desc LIMIT #{offSet},#{limit}; (推荐,代码层可控) </select>
分析:方法二的写法,需要再请求参数中额外设置两个get函数,如下:
@Data public class QueryParameterVO { private List<String> ids; private List<Integer> statusList; // 前端传入的页码 private int pageNo; // 从1开始 // 每页的条数 private int pageSize; // 数据库的偏移 private int offSet; // 数据库的大小限制 private int limit; // 这里重写offSet和limit的get方法 public int getOffSet() { return (pageNo-1)*pageSize; } public int getLimit() { return pageSize; } }
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