注：本文代碼樣例及sql腳本均已上傳至gitee：spring-boot-mybatis-plus學習
基本查詢
/**
* id=?
*/
@Test
void selectById() {
User user = mapper.selectById(1087982257332887553L);
System.out.println(user);
}
/**
* id IN ( ? , ? , ? )
*/
@Test
void retrieveByIds() {
List<User> users = mapper.selectBatchIds(Arrays.asList(8, 9, 10));
users.forEach(System.out::println);
}
/**
* 根據map查詢,key為column,value為具體的值
* name = ? AND age = ?
*/
@Test
void retrieveByMap() {
Map<String, Object> map = new HashMap<>();
map.put("name", "大boss");
map.put("age", "40");
List<User> users = mapper.selectByMap(map);
users.forEach(System.out::println);
}
條件構造器查詢
地址: 條件構造器
/**
* 名字中包含雨並且年齡小於40
* name like '%雨%' and age<40
*/
@Test
void selectByWrapper1() {
QueryWrapper<User> wrapper = new QueryWrapper<>();
wrapper.like("name", "雨")
.lt("age", 40);
List<User> users = mapper.selectList(wrapper);
users.forEach(System.out::println);
}
/**
* 名字中包含雨年並且齡大於等於20且小於等於40並且email不為空
* name like '%雨%' and age between 20 and 40 and email is not null
*/
@Test
void selectByWrapper2() {
QueryWrapper<User> wrapper = new QueryWrapper<>();
wrapper.like("name", "雨")
.between("age", 20, 40)
.isNotNull("email");
List<User> users = mapper.selectList(wrapper);
users.forEach(System.out::println);
}
/**
* 名字為王姓或者年齡大於等於25，按照年齡降序排列，年齡相同按照id升序排列
* name like '王%' or age>=25 order by age desc,id asc
*/
@Test
void selectByWrapper3() {
QueryWrapper<User> wrapper = new QueryWrapper<>();
wrapper.likeRight("name", "王")
.or().ge("age", 25)
.orderByDesc("age")
.orderByAsc("id");
List<User> users = mapper.selectList(wrapper);
users.forEach(System.out::println);
}
/**
* 創建日期為2019年2月14日並且直屬上級為名字為王姓
* date_format(create_time,'%Y-%m-%d')='2019-02-14' and
* manager_id in (select id from user where name like '王%')
*/
@Test
void selectByWrapper4() {
QueryWrapper<User> wrapper = new QueryWrapper<>();
wrapper.apply("date_format(create_time,'%Y-%m-%d')={0}", "2019-02-14")
.inSql("manager_id", "select id from user where name like '王%'");
List<User> users = mapper.selectList(wrapper);
users.forEach(System.out::println);
}
/**
* and中傳入lambda
* <p>
* 名字為王姓並且（年齡小於40或郵箱不為空）
* name like '王%' and (age<40 or email is not null)
*/
@Test
void selectByWrapper5() {
QueryWrapper<User> wrapper = new QueryWrapper<>();
wrapper.likeRight("name", "王").
and(wq -> wq.lt("age", 40)
.or().isNotNull("email"));
List<User> users = mapper.selectList(wrapper);
users.forEach(System.out::println);
}
/**
* 名字為王姓或者（年齡小於40並且年齡大於20並且郵箱不為空）
* name like '王%' or (age<40 and age>20 and email is not null)
*/
@Test
void selectByWrapper6() {
QueryWrapper<User> wrapper = new QueryWrapper<>();
wrapper.likeRight("name", "王").
or(wq -> wq.lt("age", 40)
.gt("age", 20)
.isNotNull("email"));
List<User> users = mapper.selectList(wrapper);
users.forEach(System.out::println);
}
/**
* （ 年齡小於40或郵箱不為空）並且名字為王姓
* (age<40 or email is not null) and name like '王%'
*/
@Test
void selectByWrapper7() {
QueryWrapper<User> wrapper = new QueryWrapper<>();
wrapper.nested(wq -> wq.lt("age", 40)
.or().isNotNull("email"))
.likeRight("name", "王");
List<User> users = mapper.selectList(wrapper);
users.forEach(System.out::println);
}
/**
* 年齡為30、31、34、35
*/
@Test
void selectByWrapper8() {
QueryWrapper<User> wrapper = new QueryWrapper<>();
wrapper.in("age", Arrays.asList(30, 31, 34, 35));
List<User> users = mapper.selectList(wrapper);
users.forEach(System.out::println);
}
/**
* 只返回滿足條件的其中一條語句即可 limit 1
*/
@Test
void selectByWrapper9() {
QueryWrapper<User> wrapper = new QueryWrapper<>();
wrapper.in("age", Arrays.asList(30, 31, 34, 35)).last("limit 1");
List<User> users = mapper.selectList(wrapper);
users.forEach(System.out::println);
}
指定列與排除列
/**
* 查詢指定列
* SELECT id,name FROM user WHERE (name LIKE ?)
*/
@Test
void selectPart1() {
QueryWrapper<User> wrapper = new QueryWrapper<>();
wrapper.select("id", "name").like("name", "雨");
List<User> users = mapper.selectList(wrapper);
users.forEach(System.out::println);
}
/**
* 排除指定列
* SELECT id,name,age,manager_id FROM user WHERE (name LIKE ?)
*/
@Test
void selectPart2() {
QueryWrapper<User> wrapper = new QueryWrapper<>();
wrapper.select(User.class, info -> !info.getColumn().equals("create_time") &&
!info.getColumn().equals("email")
).like("name", "雨");
List<User> users = mapper.selectList(wrapper);
users.forEach(System.out::println);
}
Condition處理參數
@Test
void testCondition(){
String name = "王";
String email = "";
//withOutCondition(name,email);
withCondition(name,email);
}
private void withOutCondition(String name,String email){
QueryWrapper<User> wrapper = new QueryWrapper<>();
if(StringUtils.isNotBlank(name)){
wrapper.like("name",name);
}
if(StringUtils.isNotBlank(email)){
wrapper.like("email",email);
}
List<User> users = mapper.selectList(wrapper);
users.forEach(System.out::println);
}
private void withCondition(String name,String email){
QueryWrapper<User> wrapper = new QueryWrapper<>();
wrapper.like(StringUtils.isNotBlank(name),"name",name)
.like(StringUtils.isNotBlank(email),"email",email);
List<User> users = mapper.selectList(wrapper);
users.forEach(System.out::println);
}
以實體作為參數
/**
* WHERE name=? AND age=?
* 以實體為參數 和普通設置參數 互不干擾, 都會存在, 使用時需慎重
* 以實體為參數,默認是等值的,需要使用@TableField注解,並注明sqlCondition
*/
@Test
void selectByWrapperEntity(){
User user = new User();
user.setName("天喬巴夏");
user.setAge(20);
QueryWrapper<User> wrapper = new QueryWrapper<>(user);
List<User> users = mapper.selectList(wrapper);
users.forEach(System.out::println);
}
@TableField(value = "name",condition = SqlCondition.LIKE) //指定字段名
private String name;
AllEq的使用
@Test
void selectByWrapperAllEq(){
QueryWrapper<User> wrapper = new QueryWrapper<>();
Map<String,Object> params = new HashMap<>();
params.put("name","天喬巴夏");
params.put("age",null); // age is null , 可以通過 下面這句設置 false
wrapper.allEq(params,false);
List<User> users = mapper.selectList(wrapper);
users.forEach(System.out::println);
}
@Test
void selectByWrapperAllEq2() {
QueryWrapper<User> wrapper = new QueryWrapper<>();
Map<String, Object> params = new HashMap<>();
params.put("name", "天喬巴夏");
params.put("age", null); // age is null , 可以通過 下面這句設置 false
wrapper.allEq((k, v) -> !k.equals("name"), params, false);
List<User> users = mapper.selectList(wrapper);
users.forEach(System.out::println);
}
自定義查詢
注解形式
public interface UserMapper extends BaseMapper<User> {
@Select("select * from user ${ew.customSqlSegment}")
List<User> selectAll(@Param(Constants.WRAPPER)Wrapper<User> wrapper);
}
/**
* 測試自定義方法 注解
*/
@Test
void selectByCustomAnno(){
QueryWrapper<User> wrapper = new QueryWrapper<>();
wrapper.eq("name","天喬巴夏");
List<User> users = mapper.selectAll(wrapper);
users.forEach(System.out::println);
}
xml形式
public interface UserMapper extends BaseMapper<User> {
List<User> selectAll2(@Param(Constants.WRAPPER)Wrapper<User> wrapper);
}
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.hyh.mybatisplus.mapper.UserMapper">
<select id="selectAll2" resultType="com.hyh.mybatisplus.entity.User">
select * from user ${ew.customSqlSegment}
</select>
</mapper>
其他的查詢
/**
* 優雅返回指定字段的結果
*/
@Test
void selectByWrapperMaps1() {
QueryWrapper<User> wrapper = new QueryWrapper<>();
wrapper.like("name", "雨")
.lt("age", 40)
.select("id","name");
List<Map<String, Object>> mapList = mapper.selectMaps(wrapper);
mapList.forEach(System.out::println);
}
/**
* 按照直屬上級分組，查詢每組的平均年齡、最大年齡、最小年齡。
* 並且只取年齡總和小於500的組。
*
* select avg(age) avg_age,min(age) min_age,max(age) max_age
* from user
* group by manager_id
* having sum(age) <500
*/
@Test
void selectByWrapperMaps2() {
QueryWrapper<User> wrapper = new QueryWrapper<>();
wrapper.select("avg(age) avg_age","min(age) min_age","max(age) max_age")
.groupBy("manager_id").having("sum(age)<{0}",500);
List<Map<String, Object>> mapList = mapper.selectMaps(wrapper);
mapList.forEach(System.out::println);
}
/**
* 只返回一列
*/
@Test
void selectByWrapperObjs() {
QueryWrapper<User> wrapper = new QueryWrapper<>();
wrapper.select("avg(age) avg_age","min(age) min_age","max(age) max_age")
.groupBy("manager_id").having("sum(age)<{0}",500);
List<Object> objects = mapper.selectObjs(wrapper);
objects.forEach(System.out::println);
}
/**
* 查個數
*/
@Test
void selectCount() {
QueryWrapper<User> wrapper = new QueryWrapper<>();
wrapper.like("name","雨");
Integer cnt = mapper.selectCount(wrapper);
System.out.println(cnt);
}
/**
* 查一個實體
*/
@Test
void selectOne(){
QueryWrapper<User> wrapper = new QueryWrapper<>();
wrapper.eq("name","天喬巴夏");
User user = mapper.selectOne(wrapper);
System.out.println(user);
}
/**
* lambda構造,編譯時檢查字段信息,防止誤寫
*/
@Test
void selectLambda(){
//LambdaQueryWrapper<User> lambda = new QueryWrapper<User>().lambda();
//LambdaQueryWrapper<User> lambdaQueryWrapper = new LambdaQueryWrapper<>();
LambdaQueryWrapper<User> lambdaQuery = Wrappers.<User>lambdaQuery();
lambdaQuery.like(User::getName,"雨").lt(User::getAge,40);
// where name like '%雨%'
List<User> users = mapper.selectList(lambdaQuery);
users.forEach(System.out::println);
}