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最近在学习mybatisPlus时总结了一些常用的有关条件构造器的查询方法，以此做下记录，方便学习使用！
eq: 等于 =
例子：eq("name", "老王")--->name = ‘老王‘
ne: 不等于 <>
例子：ne("name", "老王")--->name <> ‘老王‘
gt: 大于 >
例子：gt("age", 18)--->age > 18
ge: 大于等于 >=
例子：ge("age", 18)--->age >= 18
lt: 小于 <
例子：lt("age", 18)--->age < 18
le: 小于等于 <=
例子：le("age", 18)--->age <= 18
between: 值 1 AND 值 2
例子：between("age", 18, 30)--->age between 18 and 30
notBetween: Not BETWEEN 值 1 AND 值 2
例子：notBetween("age", 18, 30)--->age not between 18 and 30
like: like‘%值%‘
例子：like("name", "王")--->name like ‘%王%‘
notLike: NOT LIKE ‘%值%‘
例子：notLike("name", "王")--->name not like ‘%王%‘
likeLeft: Like‘%值‘
例子：likeLeft("name", "王")--->name like ‘%王‘
likeRight: LIKE‘值%‘
例子：likeRight("name", "王")--->name like ‘王%‘
isNull: 字段 IS NULL
例子：isNull("name")--->name is null
isNotNull:字段 IS NOT NULL
例子：isNotNull("name")--->name is not null
in: 字段IN(value.get(0),value.get(1),...)
例子：in("age",{1,2,3})--->age in (1,2,3)
字段 IN (v0, v1, ...)
例子：in("age", 1, 2, 3)--->age in (1,2,3)
notIn: 字段 IN (value.get(0), value.get(1), ...)
例子：notIn("age",{1,2,3})--->age not in (1,2,3)
字段 NOT IN (v0, v1, ...)
例子：notIn("age", 1, 2, 3)--->age not in (1,2,3)
inSql: 字段 IN（SQL语句）
例子1：inSql("age", "1,2,3,4,5,6")--->age in (1,2,3,4,5,6)
例子2：inSql("id", "select id from table where id < 3")--->id in (select id from table where id < 3)
notInSql: 字段NOT IN (sql语句)
例子1：notInSql("age", "1,2,3,4,5,6")--->age not in (1,2,3,4,5,6)
例子2：notInSql("id", "select id from table where id < 3")--->age not in (select id from table where id < 3)
分组：GROUP BY 字段，...
例子：groupBy("id", "name")--->group by id,name
升序: ORDER BY 字段，...ASC
例子：orderByAsc("id", "name")--->order by id ASC,name ASC
降序：ORDER BY 字段，...DESC
例子：orderByDesc("id", "name")--->order by id DESC,name DESC
排序：OREDR BY 字段，...
例子：orderBy(true, true, "id", "name")--->order by id ASC,name ASC
聚合函数作为条件：HAVING (sql语句)
例子1：having("sum(age) > 10")--->having sum(age) > 10（有sql注入风险）
例子2：having("sum(age) > {0}", 11)--->having sum(age) > 11（推荐使用）
拼接 OR： or()
例子：eq("id",1).or().eq("name","老王")--->id = 1 or name = ‘老王‘
注意事项：主动调用or表示紧接着下一个方法不是用and连接!(不调用or则默认为使用and连接)
OR 嵌套：
例子：or(i -> i.eq("name", "李白").ne("status", "活着"))--->or (name = ‘李白‘ and status <> ‘活着‘)
AND 嵌套：
例子：and(i -> i.eq("name", "李白").ne("status", "活着"))--->and (name = ‘李白‘ and status <> ‘活着‘)
nested：正常嵌套 不带AND 或者 OR
例子：nested(i -> i.eq("name", "李白").ne("status", "活着"))--->(name = ‘李白‘ and status <> ‘活着‘)
拼接 sql：apply
例子1：apply("id = 1")--->id = 1
例子2：apply("date_format(dateColumn,‘%Y-%m-%d‘) = ‘2008-08-08‘")
--->date_format(dateColumn,‘%Y-%m-%d‘) = ‘2008-08-08‘")
例子3：apply("date_format(dateColumn,‘%Y-%m-%d‘) = {0}", "2008-08-08")
--->date_format(dateColumn,‘%Y-%m-%d‘) = ‘2008-08-08‘")
注意事项：该方法可用于数据库函数 动态入参的params对应前面applySql内部的{index}部分.这样是不会有sql注入风险的,反之会有!
无视优化规则直接拼接到 sql 的最后：last
例子：last("limit 1")
注意事项：只能调用一次,多次调用以最后一次为准 有sql注入的风险,请谨慎使用
exists：拼接EXISTS（sql语句）
例子：exists("select id from table where age = 1")--->exists (select id from table where age = 1)
在学习过程中通过几个小例子(需求)验证了一下：
1.名字中包含雨并且年龄小于40 name like ‘%雨%‘ and age<40
@Test
public void selectByWrapper(){
QueryWrapper<User> queryWrapper = new QueryWrapper<User>();
//QueryWrapper<User> query = Wrappers.<User>query();
queryWrapper.like("name","雨").lt("age",40);
List<User> userList = userMapper.selectList(queryWrapper);
userList.forEach(System.out::println);
}
结果展示：
2.名字中包含雨年并且龄大于等于20且小于等于40并且email不为空 name like ‘%雨%‘ and age between 20 and 40 and email is not null
@Test
public void selectByWrapper6(){
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper.likeRight("name","王").or(qw->qw.lt("age",40).gt("age",20).isNotNull("email"));
List<User> userList = userMapper.selectList(queryWrapper);
for (User user : userList) {
System.out.println(user);
}
}
结果展示：
3.名字为王姓或者年龄大于等于25，按照年龄降序排列，年龄相同按照id升序排列 name like ‘王%‘ or age>=25 order by age desc,id asc
@Test
public void selectByWrapper3(){
QueryWrapper<User> queryWrapper = new QueryWrapper<User>();
queryWrapper.likeRight("name","王").or().ge("age",25).orderByDesc("age").orderByAsc("id");
List<User> userList = userMapper.selectList(queryWrapper);
userList.forEach(System.out::println);
}
结果展示：
4.创建日期为2019年2月14日并且直属上级为名字为王姓 date_format(create_time,‘%Y-%m-%d‘)=‘2019-02-14‘ and manager_id in (select id from user where name like ‘王%‘)
@Test
public void selectByWrapper4(){
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper.apply("date_format(create_time,‘%Y-%m-%d‘)={0}","2019-02-14")
.inSql("manager_id","select id from mp_user where name like ‘王%‘");
List<User> userList = userMapper.selectList(queryWrapper);
userList.forEach(System.out::println);
}
结果展示：
5.名字为王姓并且（年龄小于40或邮箱不为空） name like ‘王%‘ and (age<40 or email is not null)
@Test
public void selectByWrapper5(){
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper.likeRight("name","王").and(wq->wq.lt("age",40).or().isNotNull("email"));
List<User> userList = userMapper.selectList(queryWrapper);
userList.forEach(System.out::println);
}
结果展示：
6.名字为王姓或者（年龄小于40并且年龄大于20并且邮箱不为空） name like ‘王%‘ or (age<40 and age>20 and email is not null)
@Test
public void selectByWrapper6(){
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper.likeRight("name","王").or(qw->qw.lt("age",40).gt("age",20).isNotNull("email"));
List<User> userList = userMapper.selectList(queryWrapper);
for (User user : userList) {
System.out.println(user);
}
}
结果展示：
7.（年龄小于40或邮箱不为空）并且名字为王姓 (age<40 or email is not null) and name like ‘王%‘
@Test
public void selectByWrapper7(){
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper.nested(wq->wq.lt("age",40).or().isNotNull("email")).likeRight("name","王");
List<User> userList = userMapper.selectList(queryWrapper);
for (User user : userList) {
System.out.println(user);
}
}
结果展示：
8.年龄为30、31、34、35 age in (30、31、34、35)
@Test
public void selectByWrapper8(){
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper.in("age",Arrays.asList(30,31,34,35));
//queryWrapper.in("age",30,31,34,35);
List<User> userList = userMapper.selectList(queryWrapper);
for (User user : userList) {
System.out.println(user);
}
}
结果展示：
9、只返回满足条件的其中一条语句即可 limit 1
@Test
public void selectByWrapper9(){
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper.in("age",Arrays.asList(30,31,34,35)).last("limit 1");
List<User> userList = userMapper.selectList(queryWrapper);
for (User user : userList) {
System.out.println(user);
}
}
结果展示：
以上仅为一些简单的需求，后续学习使用复杂的用法再进行记录整理。。。。。。。
原文地址：https://www.cnblogs.com/zhukf/p/12144072.html