mybatis plus常用操作

1.条件更新指定字段

UpdateWrapper<ExamParticipation> updateWrapper = new UpdateWrapper<>();
updateWrapper.lambda()
    .eq(ExamParticipation::getId, id)
    .set(ExamParticipation::getField1, value1)
    .set(ExamParticipation::getField2, value2)
    .set(ExamParticipation::getField3, value3);

int rows = examParticipationMapper.update(null, updateWrapper);

2.条件批量更新

List<Long> ids = Arrays.asList(1L, 2L, 3L);
List<String> values = Arrays.asList("value1", "value2", "value3");

UpdateWrapper<ExamParticipation> updateWrapper = new UpdateWrapper<>();
updateWrapper.lambda()
    .in(ExamParticipation::getId, ids)
    .set(ExamParticipation::getField1, values);

int rows = examParticipationMapper.update(null, updateWrapper);

3.批量新增

List<ExamParticipation> examParticipations = new ArrayList<>();
examParticipations.add(new ExamParticipation(field1, field2, field3));
examParticipations.add(new ExamParticipation(field1, field2, field3));
examParticipations.add(new ExamParticipation(field1, field2, field3));

boolean success = examParticipationService.saveBatch(examParticipations);

4.批量新增部分字段

另外，如果你只想新增部分字段，可以使用 saveBatchSomeColumn 方法，

List<ExamParticipation> examParticipations = new ArrayList<>();
examParticipations.add(new ExamParticipation(field1, field2, field3));
examParticipations.add(new ExamParticipation(field1, field2, field3));
examParticipations.add(new ExamParticipation(field1, field2, field3));

boolean success = examParticipationService.saveBatchSomeColumn(examParticipations);

5.联表查询

public List<Order> getOrdersWithUser() {
    return orderMapper.selectList(new QueryWrapper<Order>()
        .select("order.*", "user.user_name")
        .leftJoin("user", "user.id = order.user_id")
        .eq("order.status", "paid")
    );
}