当使用 Spring JPA EntityManager 本机查询删除数据库时，遇到 SQLGrammarException答案

【问题标题】：when drop a database using Spring JPA EntityManager native query, runs into SQLGrammarException当使用 Spring JPA EntityManager 本机查询删除数据库时，遇到 SQLGrammarException
【发布时间】：2021-12-02 19:05:38
【问题描述】：

我尝试使用 EntityManager 原生查询删除数据库，但它抛出 SQLGrammarException

代码sn-p：

entityManager.createNativeQuery("DROP DATABASE :schema").setParameter("schema", test_schema).executeUpdate();

它抛出：

Caused by: 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 ''test_schema'' at line 1
    at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:120) ~[mysql-connector-java-8.0.21.jar:8.0.21]
    at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97) ~[mysql-connector-java-8.0.21.jar:8.0.21]
    at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122) ~[mysql-connector-java-8.0.21.jar:8.0.21]
    at com.mysql.cj.jdbc.ClientPreparedStatement.executeInternal(ClientPreparedStatement.java:953) ~[mysql-connector-java-8.0.21.jar:8.0.21]
    at com.mysql.cj.jdbc.ClientPreparedStatement.executeUpdateInternal(ClientPreparedStatement.java:1092) ~[mysql-connector-java-8.0.21.jar:8.0.21]
    at com.mysql.cj.jdbc.ClientPreparedStatement.executeUpdateInternal(ClientPreparedStatement.java:1040) ~[mysql-connector-java-8.0.21.jar:8.0.21]
    at com.mysql.cj.jdbc.ClientPreparedStatement.executeLargeUpdate(ClientPreparedStatement.java:1347) ~[mysql-connector-java-8.0.21.jar:8.0.21]
    at com.mysql.cj.jdbc.ClientPreparedStatement.executeUpdate(ClientPreparedStatement.java:1025) ~[mysql-connector-java-8.0.21.jar:8.0.21]
    at com.zaxxer.hikari.pool.ProxyPreparedStatement.executeUpdate(ProxyPreparedStatement.java:61) ~[HikariCP-3.4.5.jar:na]
    at com.zaxxer.hikari.pool.HikariProxyPreparedStatement.executeUpdate(HikariProxyPreparedStatement.java) ~[HikariCP-3.4.5.jar:na]
    at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:197) ~[hibernate-core-5.4.21.Final.jar:5.4.21.Final]

【问题讨论】：

test_schema 的值是多少？里面有引号吗？
test_schema 是字符串变量

标签： java mysql hibernate spring-data-jpa

【解决方案1】：

经过多次尝试，我认为 JPQL 不支持它。所以我使用 JDBC 来做到这一点。

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

public class JDBCExample {
   static final String DB_URL = "jdbc:mysql://localhost/";
   static final String USER = "root";
   static final String PASS = "root";

   public static void main(String[] args) {
      // Open a connection
      try(Connection conn = DriverManager.getConnection(DB_URL, USER, PASS);
         Statement stmt = conn.createStatement();
      ) {             
         String sql = "DROP DATABASE database_name";
         stmt.executeUpdate(sql);
         System.out.println("Database dropped successfully...");      
      } catch (SQLException e) {
         e.printStackTrace();
      } 
   }
}

【讨论】：