如果不存在则创建一个新数据库

Question

我正在制作一个数据库检查器（如果它存在的话）。如果不是，它应该创建一个新数据库和 tables.

我的问题是我无法创建 table，只能创建数据库。

private void Connect() throws Exception
  {
   try {
    Class.forName("com.mysql.jdbc.Driver");
    con = DriverManager.getConnection("jdbc:mysql:///",
            "root", "");
    st = con.createStatement();
    String sql = "CREATE DATABASE dbproject2";
    //sql = "DROP DATABASE DBNAME";
    st.executeUpdate(sql);
    //con = DriverManager.getConnection("jdbc:mysql:///dbproject2","root", "");
    st.executeUpdate("CREATE TABLE tbl_admin(username varchar(200),password varchar(200),name varchar(200), PRIMARY KEY(username))");
    int i = st.executeUpdate("insert into tbl_admin values('admin','123456','Chris')");
    st.executeUpdate("CREATE TABLE tbl_emp(name varchar(200),department varchar(200),startTime time, PRIMARY KEY(name))");
    st.executeUpdate("CREATE TABLE tbl_records(cardNo varchar(100),holderNo varchar(100),holderName varchar(100),IODate date,IOTime time,IOGateNo varchar(100),IOGateName varchar(100),IOStatus varchar(100),departmentNo int(10), PRIMARY KEY(name))");

} catch (SQLException sqlException) {
    if (sqlException.getErrorCode() == 1007) {
        // Database already exists error
        Class.forName(Driver);      
        con = DriverManager.getConnection(url,uname,pword);
        st = con.createStatement();
        st1 = con.createStatement();
    } else {
        // Some other problems, e.g. Server down, no permission, etc
        sqlException.printStackTrace();
    }
} catch (ClassNotFoundException e) {
    // No driver class found!
}

Answer 1

您需要重新连接新数据库并使用这些创建新语句。
例如

con = DriverManager.getConnection("jdbc:mysql:///",
            "root", "");
    st = con.createStatement();
    String sql = "CREATE DATABASE dbproject2";
    //sql = "DROP DATABASE DBNAME";
    st.executeUpdate(sql);


con = DriverManager.getConnection("jdbc:mysql:///dbproject2","root", "");

    st = con.createStatement();


    st.executeUpdate("CREATE TABLE tbl_admin(username varchar(200),password varchar(200),name varchar(200), PRIMARY KEY(username))");
    int i = st.executeUpdate("insert into tbl_admin values('admin','123456','Chris')");
    st.executeUpdate("CREATE TABLE tbl_emp(name varchar(200),department varchar(200),startTime time, PRIMARY KEY(name))");
    st.executeUpdate("CREATE TABLE tbl_records(cardNo varchar(100),holderNo varchar(100),holderName varchar(100),IODate date,IOTime time,IOGateNo varchar(100),IOGateName varchar(100),IOStatus varchar(100),departmentNo int(10), PRIMARY KEY(name))");

如果不存在则创建一个新数据库

Making a new database if not existing

java

mysql

jdbc