如何使用 Java 比较 2 个数据库表

Question

我这里有一个场景，我需要使用 java 比较 2 个数据库表

第一个数据库表有

id  Name Salary
1   ABC  1000
2   XYZ  2000
3   LMN  3000

第二个数据库表有

id Name Salary
4  PQR  5000
2  XYZ  2000
1  ABC  4000
3  LMN  2500

我曾使用 list 进行比较，但有没有其他方法可以使用 selenium java 比较第一个表和第二个表。

我希望输出是

Second table has 4 rows while 1 table has 3 rows (or vice versa)
1st table LMN salary is 3000 and second table LMN salary is 2500

Answer 1

我会直接在 SQL 中进行请求的比较。这会更快。根据您需要的结果，有几种方法可以做到这一点。

由于您使用的是 Microsoft SQL，您可以通过执行以下操作以请求的格式检索行数：

SELECT 'The FirstTable has ' + cast((SELECT count(*) from FirstTable) as varchar(50)) + ' records, while the SecondTable has ' + cast((SELECT count(*) from SecondTable) as varchar(50)) + ' records';

要获得表之间的差异，您可以执行以下操作：

SELECT * FROM FirstTable
UNION 
SELECT * FROM SecondTable
EXCEPT 
SELECT * FROM FirstTable
INTERSECT
SELECT * FROM SecondTable;

然后你可以获取 ResultSet 并像这样比较条目：

while (resultSet.next())
{

  int id= rs.getInt("id");
  String name= rs.getString("name");
  int firstTableSalary = rs.getInt("salary");

  rs.next();
  int secondTableSalary = rs.getInt("salary");

  console.log(String.format("The first table salary is %d, while the second table salary is %d, name=%s, id=%d", firstTableSalary, secondTableSalary, name, id);

}

我准备了 here 一个用于检查 SQL 的小提琴。

Answer 2

使用 SQL 更容易获得工资差异

String query = "select t1.name,t1.salary t1_salary, t2.salary t2_salary" +
    " from table1 t1, table2 t2 "+
    " where t1.id=t2.id and t1.name=t2.name and t1.salary!=t2.salary";
//this will give you a result set of all the names and salaries from the two tables 
//where the salaries differ. 
Connection conn = ...
try (Statement stmt = conn.createStatement()){
    ResultSet rs = stmt.executeQuery(query);
    while (rs.next()){
        String name = rs.getString(1);
        Integer t1Salary = rs.getInt(2);
        Integer t2Salary = rs.getInt(3);
         //do something with these values
    }
    rs.close();

同样，通过查询捕获表长度

    int t1Length = 0;
    int t2Length = 0;
    rs = stmt.executeQuery("select count(*) from table1");
    while (rs.next()){
        t1Length = rs.getInt(1);
    }
    rs.close();
    rs = stmt.executeQuery("select count(*) from table2");
    while (rs.next()){
       t2Length = rs.getInt(1);
    }
    rs.close();
     //do something with the lengths
}
conn.close();