生成带有三列名称的随机 SELECT sql 总是在那里

Question

我有一个名为ReadTableConnectionInfo 的类，其中包含有关表的详细信息，例如tableName，它是columns。我编写了一个多线程代码，我应该在其中使用来自table.getColumns() 的列值生成一个随机选择 sql。

假设 table1 有 8 列，例如-

ID
CREATION
DATE
ACCOUNT
ADVERTISE
SELLERS
GEOGRAPHIC
DEMOGRAPHIC

下面是我尝试使用列生成随机选择 sql 的代码。这里table 是ReadTableConnectionInfo 对象。

@Override
public void run() {

        while (System.currentTimeMillis() <= 30 minutes) {

        final String selectSql = generateRandomSQL(table);

        preparedStatement = entry.getValue().prepareCall(selectSql);
        preparedStatement.setString(id);

        rs = preparedStatement.executeQuery();
    }
}   
    /**
     * A simple method that will construct the SQL
     * and return back
     * @param columns
     * @return sql
     */
    private String generateRandomSQL(ReadTableConnectionInfo table) {

        /* generate random columns from 
             * `table.getColumns`, not sure how to make that
             */
            final String sql = "SELECT ID, CREATION_DATE, LAST_MODIFIED_DATE,  from "+table.getTableName+" where id = ?";

        return sql;
    }

下面是我的ReadTableConncectionInfo class，它将保存 tableName 和 columns list

public class ReadTableConnectionInfo {

    public String tableName;
    public ArrayList<String> columns;

    public ArrayList<String> getColumns() {
        return columns;
    }

    public void setColumns(ArrayList<String> columns) {
        this.columns = columns;
    }

    public String getTableName() {
        return tableName;
    }

    public void setTableName(String tableName) {
        this.tableName = tableName;
    }
}

现在我需要从table.getColumns() 列表中的generateRandomSQL 方法中生成随机选择SQL。在我所有的 SELECT sql 中，我将始终拥有 ID, CREATION and DATE，除此之外，它应该是随机的

示例 SQL 示例-

`SELECT ID, CREATION, DATE, ACCOUNT from table1 where id = ?`
`SELECT ID, CREATION, DATE, ACCOUNT, ADVERTISE from table1 where id = ?`
`SELECT ID, CREATION, DATE, ACCOUNT, SELLERS from table1 where id = ?`
`SELECT ID, CREATION, DATE, GEOGRAPHIC, DEMOGRAPHIC, ADVERTISE from table1 where id = ?`
`Other possible permutations`

任何人都可以帮助我构建带有 ID、CREATION 和 DATE 的随机 SELECT sql 吗？任何建议都会有很大帮助。

Answer 1

private String generateRandomSQL(ReadTableConnectionInfo table) {
    Random r = new Random(table.getColumns.size());
    int rNumber = r.nextInt();

    List<String> suffledColumns = new ArrayList<String>(table.getColumns());
    Collections.shuffle(suffledColumns);

    String columnsList = "";

    for(int i = 0 ; i < rNumber ; i ++){
        columnsList += ("," + shuffledColumns.get(i));
    }

    final String sql = "SELECT ID, CREATION_DATE, LAST_MODIFIED_DATE" + columnsList +"  from " + table.getTableName() + " where id = ?";

        return sql;
}

Answer 2

类似的东西：

   String colPart="SELECT ID, CREATION_DATE, LAST_MODIFIED_DATE"
   Random rNo=new Random();
   int noOfCols=columns.size();
   int colCount=rNo.nextInt(noOfCols-3);
   for(int i=0;i<colCount;i++){
   string colToAdd=columns.get(3+rNo.nextInt(noOfCols-3));
   if(!colPart.contains(colToAdd))    
       colPart+=","+colToAdd;
   }        
    final String sql =colPart+" from "+table.getTableName+" where id = ?";