列名称包含下划线时的语法错误 [英] Syntax Error when the column name contains underscore
本文介绍了列名称包含下划线时的语法错误的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我可以编译但无法执行以下代码
,并出现错误(使用Postgres):
I can compile but can't execute the following code with the error (using Postgres):
Fatal database error
ERROR: syntax error at or near "as"
Position: 13
import java.sql.*;
public class JDBCExample
{
private static final String JDBC_DRIVER = "org.postgresql.Driver";
private static final String URL = "jdbc:postgresql://hostname/database";
private static final String USERNAME = "username";
private static final String PASSWORD = "password";
public static void main(String[] args) throws Exception
{
Connection dbConn = null;
Statement query = null;
ResultSet results = null;
Class.forName(JDBC_DRIVER);
try
{
dbConn = DriverManager.getConnection(URL, USERNAME, PASSWORD);
}
catch (SQLException e)
{
System.out.println("Unable to connect to database\n"+e.getMessage());
System.exit(1);
}
try
{
query = dbConn.createStatement();
results = query.executeQuery("select 20_5 as name from flowshop_optimums");
while (results.next())
{
System.out.println(results.getString("name"));
}
dbConn.close();
}
catch (SQLException e)
{
System.out.println("Fatal database error\n"+e.getMessage());
try
{
dbConn.close();
}
catch (SQLException x) {}
System.exit(1);
}
} // main
} // Example
推荐答案
不是下划线,而是列名以数字开头的事实。您需要对此进行转义。
It's not the underscore, it's the fact that the column name starts with a number. You'd need to escape this.
对于MySQL,请使用反引号。
For MySQL, use backticks.
select `20_5` as name from flowshop_optimums
对于SQL Server,请使用方括号。
For SQL Server, use square brackets.
select [20_5] as name from flowshop_optimums
对于PostgreSQL,请使用双引号。
For PostgreSQL, use double quotes.
select "20_5" as name from flowshop_optimums
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