mybatis-plus自带QueryWrapper自定义sql实现复杂查询实例详解

常用写法

xxxDO=实体类，相当于:select name, id from xxx group by name where delete_flag = 0 and status = 0

LambdaQueryWrapper<xxxDO> queryWrapper = Wrappers.lambdaQuery(); queryWrapper.select(xxxDO::getName, DO::getId); queryWrapper.eq(xxxDO::getDeleteFlag, 0); queryWrapper.eq(xxxDO::getStatus, 0); queryWrapper.groupBy(xxxDO::getName); List<xxxDO> list = getBaseMapper().selectList(queryWrapper);

全选代码

复制

自定义sql

xxxDO=实体类，相当于:

select sex, ifnull(count(id), 0) AS num, CASE WHEN sex = 1 THEN 男 WHEN sex = 0 THEN 女 ELSE 未知 END AS sexStr from xxx group by sex where status = 0

LambdaQueryWrapper<xxxDO> queryWrapper = new QueryWrapper<xxxDO>() .select(“sex, ifnull(count(id), 0) AS num, CASE WHEN sex = 1 THEN 男 WHEN sex = 0 THEN 女 ELSE 未知 END AS sexStr”).lambda(); queryWrapper.eq(xxxDO::getStatus, 0); queryWrapper.groupBy(xxxDO::getSex); List<Map<String, Object>> mapList = getBaseMapper().selectMaps(queryWrapper); Map<String, String> registerNumMap = new HashMap<>(mapList.size()); for (Map<String, Object> map : mapList) { String key = String.valueOf(map.get(“sexStr”)); String num = String.valueOf(map.get(“num”)); registerNumMap.put(key, num); }

全选代码

复制

返回结果是一个list, 里面的map key是查询的属性名， value是参数值。伪代码示意：

list[0] map[0] (sex=1) map[1] (num=5) map[2] (sexStr=男)list[1] map[0] (sex=1) map[1] (num=5) map[2] (sexStr=男)

偶然而发，记录一下

补充: 查询条件中使用函数apply

queryWrapper.apply(“INET_ATON(qsip) <= INET_ATON({0})”, ipQuery); queryWrapper.apply(“INET_ATON(zzip) >= INET_ATON({0})”, ipQuery);

全选代码

复制

补充: 末尾sql追加last

queryWrapper.last(” order by id asc”); queryWrapper.last(“limit 1”);

全选代码

复制

补充:排序

// last也可以追加limit 这里用page接口 IPage<Entity> buildPage = new Page<>(0, 200); // ServiceImpl的page调用的是baseMapper的selectPage, getBaseMapper().selectPage() IPage<Entity> page = page(buildPage, queryWrapper);

全选代码

复制

sql打印

补充：Mybatis-Plus QueryWrapper +sql自定义查询

一：需要自定义的QueryWrapper查询工具类，定义查询规则

public static final String SQL_RULES_COLUMN = “SQL_RULES_COLUMN”; private static final String BEGIN = “_begin”; // 字段范围查询开始标识 private static final String END = “_end”; // 字段范围查询结束标识 private static final String STAR = “*”; // 字段模糊查询标识 private static final String COMMA = “,”; private static final String NOT_EQUAL = “!”;

全选代码

复制

二：正常的QueryWrapper查询，在mapper文件中使用 @Param(Constants.WRAPPER)

List<Emdj> listAll(IPage<Emdj> page, @Param(Constants.WRAPPER) QueryWrapper<Emdj> queryWrapper);

xml文件中使用ew.customSqlSegment，<where>标签可以不加

<select id=“listAll” resultType=“net.zazn.modules.discipline.entity.Emdj”> select id,lffh,xm,jsh,szrq,emlx,spzt,gjmj,flag,jlzt from emdj <where>${ew.customSqlSegment}</where> </select>

全选代码

复制