The difference between statement and Preparedstatement and how to use placeholders

Statement and PreparedStatement The difference between

First of all, let's talk about the connection between the two ：

1. PreparedStatement Inherited from Statement
2. PreparedStatement And Statement It's all interfaces

Then there is the difference between the two ：

1. PreaparedStatement It will be precompiled , and Statement Will not precompile
   So when we operate , Sometimes I will consider which one to use .
   First, let's make it clear ,PreparedStatement The object cost of is higher than Statement Big , however , It will precompile , in other words , The next time you use this object , Will not compile again , This saves compilation time , and Statement There will be no precompiling
   therefore , When we need batch processing , Just use PreparedStatement, also PreparedStatement Supports the use of placeholders
   When we only need one-time access Statement.

Here we extend the use of placeholders

String sql = ("insert into student values(?,?)");/ Use it here ？ Instead of characters 
PreparedStatement preparedStatement = connection.prepareStatement(sql);

 When we need to use placeholders ：
preparedStatement.setInt(1,6);
preparedStatement.setString(2, Zhang San );
 Be careful , here student The column names of the tables are ：id int,name varchar（20）
 We use set when , The first parameter is from 1 Start writing , The second parameter is the content of the placeholder 
 For example, the above code , Inserted in table id:6 name: Zhang San   A line