ResultSet rs=statement.executeQuery("select * from test where ID='"+name+"'");
if(rs==null)
{System.out.println("记录不存在");}
else
{System.out.println("记录存在");}这里我给的name的ID无论在数据库中是否存在,都是输出"记录存在"
如何修改?求教
if(rs==null)
{System.out.println("记录不存在");}
else
{System.out.println("记录存在");}这里我给的name的ID无论在数据库中是否存在,都是输出"记录存在"
如何修改?求教
if(rs.next())
{System.out.println("记录不存在");}
else
{System.out.println("记录存在");}
ResultSet rs=statement.executeQuery(sql);
if(rs==null)
{System.out.println("记录不存在");}
else
{System.out.println("记录存在");}
改了之后还总是输出" 记录存在"
if(rs.next())之前要改什么吗?
我改了之后还是老样子
ResultSet rs=statement.executeQuery(sql);
if(rs.next())
{System.out.println("记录不存在");}
else
{System.out.println("记录存在");}
ResultSet executeQuery(String sql)
throws SQLException
Executes the given SQL statement, which returns a single ResultSet object. Parameters:
sql - an SQL statement to be sent to the database, typically a static SQL SELECT statement
Returns:
a ResultSet object that contains the data produced by the given query; never null
Throws:
SQLException - if a database access error occurs or the given SQL statement produces anything other than a single ResultSet object
查查jdk带的帮助就知道了,写着never null,永不为空