0. Foreword: this error is an error reported by using mybatis in the spring boot project to query a piece of data in the database according to the ID value

1. Error message

2021-11-14 15:37:38.168 ERROR 9936 --- [nio-8086-exec-7] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.jdbc.BadSqlGrammarException: 
### Error querying database.  Cause: java.sql.SQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 1
### The error may exist in file [E:\smallTools\idea\code\spring\springboot-new-2021_11_09\springboot-new-mybatis\target\classes\mybatis\mapper\BookMapper.xml]
### The error may involve com.feng.mybatis.mapper.BookMapper.getBookById-Inline
### The error occurred while setting parameters
### SQL: select * from book where id={#id}
### Cause: java.sql.SQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 1
; bad SQL grammar []; nested exception is java.sql.SQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 1] with root cause

java.sql.SQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 1
	at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:120) ~[mysql-connector-java-8.0.27.jar:8.0.27]

2. Mapper.xml file content

<select id="getBookById" parameterType="com.feng.mybatis.bean.Book">
        select * from book where id={#id}
</select>

3. Error reason: the SQL statement is written incorrectly. It should be where id = #{id}

<select id="getBookById" parameterType="com.feng.mybatis.bean.Book">
        select * from book where id=#{id}
</select>