mybatis if else
时间: 2023-10-26 16:06:54 浏览: 47
mybatis中的if-else语句用于在SQL语句中进行条件判断。在<choose>标签内,可以使用<when>标签来定义条件,如果条件成立,则执行<when>标签内的SQL语句;如果条件不成立,则继续判断下一个<when>标签,如果所有的<when>标签都不满足条件,则执行<otherwise>标签内的SQL语句。
在引用中的示例中,当title不为空时,会执行"AND title like #{title}"这句SQL;当author不为空且author.name不为空时,会执行"AND author_name like #{author.name}"这句SQL;否则,执行"AND featured = 1"这句SQL。
相关问题
mybatis if else
MyBatis provides a way to conditionally control the generation of SQL statements using the `<if>` and `<otherwise>` tags. These tags allow you to define conditional logic within your SQL mappings.
Here's an example of how to use `<if>` and `<otherwise>` tags in MyBatis:
```xml
<select id="getUserById" resultType="User">
SELECT * FROM users
WHERE id = #{id}
<if test="isAdmin">
AND role = 'admin'
</if>
</select>
```
In this example, the SQL statement will include an additional condition (`AND role = 'admin'`) only if the `isAdmin` parameter is true. If `isAdmin` is false or not provided, the condition will be skipped.
You can also use the `<else>` tag to specify an alternative condition when `<if>` is not met:
```xml
<select id="getUserById" resultType="User">
SELECT * FROM users
WHERE
<if test="isAdmin">
role = 'admin'
</if>
<otherwise>
role = 'user'
</otherwise>
</select>
```
In this example, if the `isAdmin` parameter is true, the SQL statement will include `role = 'admin'`. Otherwise, it will include `role = 'user'`.
These are just simple examples of how to use `<if>`, `<otherwise>`, and `<else>` tags in MyBatis. You can combine multiple conditions, use dynamic parameters, and perform more complex logic using these tags.
mybatis if else写法
MyBatis是一种Java持久化框架,它提供了一种简单且灵活的方式来访问数据库。在MyBatis中,我们可以使用if-else语句来动态生成SQL语句。
在MyBatis中,if-else语句可以用于在SQL语句中添加条件判断。以下是if-else的写法示例:
1. 使用if标签:
```
<select id="getUserList" resultType="User">
SELECT * FROM user
WHERE 1=1
<if test="name != null">
AND name = #{name}
</if>
<if test="age != null">
AND age = #{age}
</if>
</select>
```
在上述示例中,如果传入的name参数不为空,则会添加name = #{name}的条件;如果传入的age参数不为空,则会添加age = #{age}的条件。
2. 使用choose、when和otherwise标签:
```
<select id="getUserList" resultType="User">
SELECT * FROM user
WHERE 1=1
<choose>
<when test="name != null">
AND name = #{name}
</when>
<when test="age != null">
AND age = #{age}
</when>
<otherwise>
AND status = 'active'
</otherwise>
</choose>
</select>
```
在上述示例中,如果传入的name参数不为空,则会添加name = #{name}的条件;如果传入的age参数不为空,则会添加age = #{age}的条件;如果name和age都为空,则会添加status = 'active'的条件。
这些是MyBatis中if-else语句的常见写法。你可以根据具体的业务需求和条件来灵活运用它们。