Java 将两个表相互比较并打印出差异

我的MySQL中有两个列完全相同的表，我们可以称它们为id、name、path、date。现在我想对这两个表进行比较，以了解表1和表2的区别，以及表2和表1的区别。我只想在我的Java程序中打印它，现在一个简单的System.out.print的差异将是完美的

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我只想检查两个表中name列中条目的差异。非常感谢您的帮助

这将连接id上的两个表，并显示名称不同的行：

select a.name, b.name 
from table1 a 
join table2 b on a.id = b.id
where a.name <> b.name

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这将连接id上的两个表，并向您显示名称不同的行：

select a.name, b.name 
from table1 a 
join table2 b on a.id = b.id
where a.name <> b.name

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我确信您可以区分两个数据库，并看到它们之间的差异，比如testdb和proddb

这是文件

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我确信您可以区分两个数据库，并看到它们之间的差异，比如testdb和proddb

这是文件

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如果您只想查看表1中存在但不在表2中的名称列表，请尝试以下操作：

SELECT a.name
FROM table1 a
LEFT JOIN table2 b ON a.name = b.name
WHERE table2.name IS NULL

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在该查询中交换table1和table2，以获取table2中不匹配的名称。

如果您只想查看table1中存在但不在table2中的名称列表，请尝试以下操作：

SELECT a.name
FROM table1 a
LEFT JOIN table2 b ON a.name = b.name
WHERE table2.name IS NULL

交换该查询中的表1和表2，以获得表2中不匹配的名称。

正确，应接受

下面是Java JDBC代码示例，显示了他的SQL代码的实际操作。我没有像问题中那样使用MySQL。相反，本例使用，创建一个临时内存中数据库

try {
    Class.forName ( "org.h2.Driver" );
} catch ( final ClassNotFoundException e ) {
    e.printStackTrace ( );
}
try ( Connection conn = DriverManager.getConnection ( "jdbc:h2:mem:trash_me_db" ) ;
      Statement stmt = conn.createStatement ( ) ) {
    String sql = null;

    // Table 1
    sql = "CREATE TABLE t1_ (\n" +
            "  id_ INT IDENTITY ,\n" +
            "  name_ VARCHAR \n" +
            ");";
    stmt.executeUpdate ( sql );
    stmt.execute ( "INSERT INTO t1_ ( name_ ) VALUES ('Jesse');" );
    stmt.execute ( "INSERT INTO t1_ ( name_ ) VALUES ('Wendy');" );
    stmt.execute ( "INSERT INTO t1_ ( name_ ) VALUES ('Lisa');" );
    stmt.execute ( "INSERT INTO t1_ ( name_ ) VALUES ('Susan');" );
    stmt.execute ( "INSERT INTO t1_ ( name_ ) VALUES ('Jimmy');" );
    stmt.execute ( "INSERT INTO t1_ ( name_ ) VALUES ('Wine');" );

    // Dump
    System.out.println ( "\nDump table t1_" );
    try ( ResultSet rs = stmt.executeQuery ( "SELECT * FROM t1_ ;" ) ) {
        while ( rs.next ( ) ) {
            final int id = rs.getInt ( "id_" );    //Retrieve by column name
            final String name = rs.getString ( "name_" );
            System.out.println ( "id: " + id + " | name: " + name );
        }
    }

    // Table 2
    sql = "CREATE TABLE t2_ (\n" +
            "  id_ INT IDENTITY ,\n" +
            "  name_ VARCHAR \n" +
            ");";
    stmt.executeUpdate ( sql );
    stmt.execute ( "INSERT INTO t2_ ( name_ ) VALUES ('Jesse');" );
    stmt.execute ( "INSERT INTO t2_ ( name_ ) VALUES ('Wendy');" );
    stmt.execute ( "INSERT INTO t2_ ( name_ ) VALUES ('Lisa');" );
    stmt.execute ( "INSERT INTO t2_ ( name_ ) VALUES ('Susan');" );
    stmt.execute ( "INSERT INTO t2_ ( name_ ) VALUES ('Jimmy');" );
    stmt.execute ( "INSERT INTO t2_ ( name_ ) VALUES ('Beer');" );

    // Dump
    System.out.println ( "\nDump table t2_" );
    try ( ResultSet rs = stmt.executeQuery ( "SELECT * FROM t2_ ;" ) ) {
        while ( rs.next ( ) ) {
            final int id = rs.getInt ( "id_" );    //Retrieve by column name
            final String name = rs.getString ( "name_" );
            System.out.println ( "id: " + id + " | name: " + name );
        }
    }

    // Difference, left.
    System.out.println ( "\nShow names that exist in t1_ but not in t2_." );
    sql = "SELECT *\n" +
            "FROM t1_ \n" +
            "LEFT JOIN t2_ ON t1_.name_ = t2_.name_\n" +
            "WHERE t2_.name_ IS NULL";
    try ( ResultSet rs = stmt.executeQuery ( sql ) ) {
        while ( rs.next ( ) ) {
            final int id = rs.getInt ( "id_" );    //Retrieve by column name
            final String name = rs.getString ( "name_" );
            System.out.println ( "id: " + id + " | name: " + name );
        }
    }

    // Difference, right.
    System.out.println ( "\nShow names that exist in t2_ but not in t1_." );
    sql = "SELECT *\n" +
            "FROM t2_ \n" +
            "LEFT JOIN t1_ ON t2_.name_ = t1_.name_\n" +
            "WHERE t1_.name_ IS NULL";
    try ( ResultSet rs = stmt.executeQuery ( sql ) ) {
        while ( rs.next ( ) ) {
            final int id = rs.getInt ( "id_" );    //Retrieve by column name
            final String name = rs.getString ( "name_" );
            System.out.println ( "id: " + id + " | name: " + name );
        }
    }


} catch ( final SQLException e ) {
    e.printStackTrace ( );
}

跑步的时候

转储表t1_ id:1 |姓名：杰西 id:2 |姓名：Wendy id:3 |姓名：丽莎 id:4 |姓名：苏珊 id:5 |姓名：吉米 id:6 |名称：葡萄酒 转储表t2_ id:1 |姓名：杰西 id:2 |姓名：Wendy id:3 |姓名：丽莎 id:4 |姓名：苏珊 id:5 |姓名：吉米 id:6 |姓名：啤酒 显示存在于t1_u1;但不存在于t2_1;中的名称。 id:6 |名称：葡萄酒 显示存在于t2_u2;中但不存在于t1_2;中的名称。 id:6 |姓名：啤酒 这是正确的，应该被接受

下面是Java JDBC代码示例，显示了他的SQL代码的实际操作。我没有像问题中那样使用MySQL。相反，本例使用，创建一个临时内存中数据库

try {
    Class.forName ( "org.h2.Driver" );
} catch ( final ClassNotFoundException e ) {
    e.printStackTrace ( );
}
try ( Connection conn = DriverManager.getConnection ( "jdbc:h2:mem:trash_me_db" ) ;
      Statement stmt = conn.createStatement ( ) ) {
    String sql = null;

    // Table 1
    sql = "CREATE TABLE t1_ (\n" +
            "  id_ INT IDENTITY ,\n" +
            "  name_ VARCHAR \n" +
            ");";
    stmt.executeUpdate ( sql );
    stmt.execute ( "INSERT INTO t1_ ( name_ ) VALUES ('Jesse');" );
    stmt.execute ( "INSERT INTO t1_ ( name_ ) VALUES ('Wendy');" );
    stmt.execute ( "INSERT INTO t1_ ( name_ ) VALUES ('Lisa');" );
    stmt.execute ( "INSERT INTO t1_ ( name_ ) VALUES ('Susan');" );
    stmt.execute ( "INSERT INTO t1_ ( name_ ) VALUES ('Jimmy');" );
    stmt.execute ( "INSERT INTO t1_ ( name_ ) VALUES ('Wine');" );

    // Dump
    System.out.println ( "\nDump table t1_" );
    try ( ResultSet rs = stmt.executeQuery ( "SELECT * FROM t1_ ;" ) ) {
        while ( rs.next ( ) ) {
            final int id = rs.getInt ( "id_" );    //Retrieve by column name
            final String name = rs.getString ( "name_" );
            System.out.println ( "id: " + id + " | name: " + name );
        }
    }

    // Table 2
    sql = "CREATE TABLE t2_ (\n" +
            "  id_ INT IDENTITY ,\n" +
            "  name_ VARCHAR \n" +
            ");";
    stmt.executeUpdate ( sql );
    stmt.execute ( "INSERT INTO t2_ ( name_ ) VALUES ('Jesse');" );
    stmt.execute ( "INSERT INTO t2_ ( name_ ) VALUES ('Wendy');" );
    stmt.execute ( "INSERT INTO t2_ ( name_ ) VALUES ('Lisa');" );
    stmt.execute ( "INSERT INTO t2_ ( name_ ) VALUES ('Susan');" );
    stmt.execute ( "INSERT INTO t2_ ( name_ ) VALUES ('Jimmy');" );
    stmt.execute ( "INSERT INTO t2_ ( name_ ) VALUES ('Beer');" );

    // Dump
    System.out.println ( "\nDump table t2_" );
    try ( ResultSet rs = stmt.executeQuery ( "SELECT * FROM t2_ ;" ) ) {
        while ( rs.next ( ) ) {
            final int id = rs.getInt ( "id_" );    //Retrieve by column name
            final String name = rs.getString ( "name_" );
            System.out.println ( "id: " + id + " | name: " + name );
        }
    }

    // Difference, left.
    System.out.println ( "\nShow names that exist in t1_ but not in t2_." );
    sql = "SELECT *\n" +
            "FROM t1_ \n" +
            "LEFT JOIN t2_ ON t1_.name_ = t2_.name_\n" +
            "WHERE t2_.name_ IS NULL";
    try ( ResultSet rs = stmt.executeQuery ( sql ) ) {
        while ( rs.next ( ) ) {
            final int id = rs.getInt ( "id_" );    //Retrieve by column name
            final String name = rs.getString ( "name_" );
            System.out.println ( "id: " + id + " | name: " + name );
        }
    }

    // Difference, right.
    System.out.println ( "\nShow names that exist in t2_ but not in t1_." );
    sql = "SELECT *\n" +
            "FROM t2_ \n" +
            "LEFT JOIN t1_ ON t2_.name_ = t1_.name_\n" +
            "WHERE t1_.name_ IS NULL";
    try ( ResultSet rs = stmt.executeQuery ( sql ) ) {
        while ( rs.next ( ) ) {
            final int id = rs.getInt ( "id_" );    //Retrieve by column name
            final String name = rs.getString ( "name_" );
            System.out.println ( "id: " + id + " | name: " + name );
        }
    }


} catch ( final SQLException e ) {
    e.printStackTrace ( );
}

跑步的时候

转储表t1_ id:1 |姓名：杰西 id:2 |姓名：Wendy id:3 |姓名：丽莎 id:4 |姓名：苏珊 id:5 |姓名：吉米 id:6 |名称：葡萄酒 转储表t2_ id:1 |姓名：杰西 id:2 |姓名：Wendy id:3 |姓名：丽莎 id:4 |姓名：苏珊 id:5 |姓名：吉米 id:6 |姓名：啤酒 显示存在于t1_u1;但不存在于t2_1;中的名称。 id:6 |名称：葡萄酒 显示存在于t2_u2;中但不存在于t1_2;中的名称。 id:6 |姓名：啤酒

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您是否只想查看表1中存在但表2中不存在的名称列表，反之亦然？确切地说，如果可能，我如何用Java查询和打印结果。我的Java程序中已经有一个工作的MySQL连接，所以我只想知道如何设置查询。您是否只想看到表1中存在但表2中不存在的名称列表，反之亦然？完全正确，如果可能，我如何用Java查询和打印结果。我的Java程序中已经有一个可以工作的MySQL连接，所以我只想知道如何设置查询。