实现获取某个字段的最大值,如sort字段,示例如下:
KapokBlockController.java
kapokBlockService.getMaxSort();
IKapokBlockService.java
package com.cmit.kapok.system.api.kapok_block; import com.cmit.kapok.system.entity.kapok_block.KapokBlock; import com.baomidou.mybatisplus.extension.service.IService; /** * <p> * 服务类 * </p> * * @author luoyihao * @since 2023-03-10 */ public interface IKapokBlockService extends IService<KapokBlock> { public int getMaxSort(); }
KapokBlockServiceImpl.java
package com.cmit.kapok.system.service.kapok_block; import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl; import com.cmit.kapok.system.api.kapok_block.IKapokBlockService; import com.cmit.kapok.system.entity.kapok_block.KapokBlock; import com.cmit.kapok.system.service.kapok_block.mapper.KapokBlockMapper; import org.springframework.stereotype.Service; import javax.annotation.Resource; /** * <p> * 服务实现类 * </p> * * @author luoyihao * @since 2023-03-10 */ @Service public class KapokBlockServiceImpl extends ServiceImpl<KapokBlockMapper, KapokBlock> implements IKapokBlockService { @Resource private KapokBlockMapper kapokBlockMapper; public int getMaxSort() { return kapokBlockMapper.getMaxSort(); } }
KapokBlockMapper.java
package com.cmit.kapok.system.service.kapok_block.mapper; import com.baomidou.mybatisplus.core.mapper.BaseMapper; import com.cmit.kapok.system.entity.kapok_block.KapokBlock; import org.apache.ibatis.annotations.Select; /** * <p> * Mapper 接口 * </p> * * @author luoyihao * @since 2023-03-10 */ public interface KapokBlockMapper extends BaseMapper<KapokBlock> { @Select("select ifnull(max(sort),0) from kapok_block") int getMaxSort(); }
即可。
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