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 queryWrapper = Wrappers.lambdaQuery(); queryWrapper.select(xxxDO::getName, DO::getId); queryWrapper.eq(xxxDO::getDeleteFlag, 0); queryWrapper.eq(xxxDO::getStatus, 0); queryWrapper.groupBy(xxxDO::getName); List list = getBaseMapper().selectList(queryWrapper);
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 queryWrapper = new QueryWrapper() .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
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);
补充: 末尾sql追加last
queryWrapper.last(" order by id asc"); queryWrapper.last("limit 1");
补充:排序
// last也可以追加limit 这里用page接口 IPage buildPage = new Page(0, 200); // ServiceImpl的page调用的是baseMapper的selectPage, getBaseMapper().selectPage() IPage page = page(buildPage, queryWrapper);
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 = "!";
二: 正常的QueryWrapper查询,在mapper文件中使用 @Param(Constants.WRAPPER)
List listAll(IPage page, @Param(Constants.WRAPPER) QueryWrapper queryWrapper);
xml文件中使用ew.customSqlSegment,标签可以不加
select id,lffh,xm,jsh,szrq,emlx,spzt,gjmj,flag,jlzt from emdj ${ew.customSqlSegment}
总结
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