java中and和or_关于MyBatis Plus中使用or和and问题
时间: 2024-02-21 13:56:44 浏览: 31
在Java中,and和or是逻辑运算符,用于对布尔值进行组合运算。and表示逻辑与,只有在两个表达式都为true时,结果才为true;or表示逻辑或,只有在两个表达式都为false时,结果才为false。
在MyBatis Plus中,使用or和and可以进行条件查询的组合。例如:
```java
QueryWrapper<User> wrapper = new QueryWrapper<>();
wrapper.eq("name", "张三").or().eq("age", 18);
List<User> userList = userMapper.selectList(wrapper);
```
上述代码中,使用了QueryWrapper构建查询条件,通过eq方法设置了name等于张三的条件,然后使用or方法和eq方法组合了一个age等于18的条件,最终执行selectList方法进行查询。
如果想要使用and方法组合条件,只需要将or方法替换为and方法即可。
需要注意的是,在使用or和and组合条件时,一定要注意条件的优先级,可以使用括号来明确条件的优先级,避免出现不符合预期的结果。
相关问题
mybatis plus or和and嵌套
MyBatis Plus provides support for both "OR" and "AND" nested conditions in query statements.
To use the "OR" nested condition, you can use the `or()` method provided by the `QueryWrapper` class. Here's an example:
```java
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper.eq("age", 20)
.or()
.eq("age", 30)
.like("name", "John");
List<User> userList = userMapper.selectList(queryWrapper);
```
In this example, the generated SQL query will have a condition for `age = 20` OR `age = 30` AND `name` LIKE '%John%'.
To use the "AND" nested condition, you don't need any special method. You can simply chain multiple conditions using the `eq()`, `like()`, etc. methods provided by the `QueryWrapper` class. Here's an example:
```java
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper.eq("age", 20)
.like("name", "John")
.ge("salary", 5000);
List<User> userList = userMapper.selectList(queryWrapper);
```
In this example, the generated SQL query will have conditions for `age = 20` AND `name` LIKE '%John%' AND `salary` >= 5000.
You can mix "OR" and "AND" nested conditions as per your requirements to construct more complex queries in MyBatis Plus.
mybatis-plusand和or
MyBatis-Plus is an open-source persistence framework for Java applications. It is an extension to the MyBatis framework, providing additional features and functionalities to simplify database operations.
When it comes to combining conditions in MyBatis-Plus, you can use both "and" and "or" operators to construct complex queries. Here's how you can use them:
1. Using "and" operator:
You can use the `and` method to add multiple conditions together, which means all conditions must be true for a record to be included in the result. Here's an example:
```java
QueryWrapper<Entity> queryWrapper = new QueryWrapper<>();
queryWrapper.eq("column1", value1)
.and(wrapper -> wrapper.eq("column2", value2)
.ne("column3", value3));
```
2. Using "or" operator:
You can use the `or` method to add multiple conditions together, which means any of the conditions can be true for a record to be included in the result. Here's an example:
```java
QueryWrapper<Entity> queryWrapper = new QueryWrapper<>();
queryWrapper.eq("column1", value1)
.or(wrapper -> wrapper.eq("column2", value2)
.ne("column3", value3));
```
With these operators, you can build complex queries by combining multiple conditions in MyBatis-Plus.
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