php mysql如何连接两个表

我有以下代码：

<?php

$records = mysql_connect('localhost', 'root', '') or die(mysql_error());

mysql_select_db('records', $records);
if(isset($_GET['src']))
{

$sql = "SELECT * FROM students where studentnumber like '%{$_GET['src']}%'";
$cnt = mysql_num_rows(mysql_query($sql));
if ($cnt == 0)
{
echo "<script>alert('No Record Found');</script>";
}

$result = mysql_query($sql, $records);
echo "<table border='0' class='table table-striped table-bordered table-hover'>";
echo "<tr class='info'><td width='10%'>Name</td><td width='11%'>Course Yr-Sec</td><td width='10%'>Student Number</td><td width='10%'>Violation</td><td width='10%'>Punishment</td><td width='9%'>Violation Date</td><td width='7%'>Punishment Date</td><td width='5%'>CS Length</td><td width='4%'>CS Done</td><td width='4%'>CS Left</td><td width='17%'><center>Action</center></td></tr></tr>";

while($row = mysql_fetch_array($result))
{
echo "<tr>";
echo "<td>";
echo $row['Lastname'];
echo ", ";
echo $row['Firstname'];
echo " ";
echo $row['Middleinitial'];
echo "</td>";
echo "<td>";
echo $row['Course'];
echo " ";
echo $row['Year'];
echo "-";
echo $row['Section'];
echo "</td>";
echo "<td>";
echo $row['Studentnumber'];
echo "</td>";
echo "<td>";
echo $row['Violation'];
echo "</td>";
echo "<td>";
echo $row['Punishment'];
echo "</td>";
echo "<td>";
echo $row['Violationdate'];
echo "</td>";
echo "<td>";
echo $row['Punishmentstartdate'];
echo "</td>";
echo "<td>";
echo $row['CSlength'];
echo "</td>";
echo "<td>";
echo $row['CSDone'];
echo "</td>";
echo "<td>";
echo $row['CSLeft'];
echo "</td>";
echo "<td>";
echo "<a href='edit.php?no={$row['ID']}'><input type='button' name='edit' value='Edit' class='btn btn-success'></a>";
echo "   <a href='delete.php?no={$row['ID']}'><input type='button' name='delete' value='Delete' class='btn btn-danger'></a>";
echo "   <input type='button' name='view' value='View' class='btn btn-info'>";echo "</td>";
echo "</tr>";
}
echo "</table>";
}
else
{
$sql = 'SELECT * FROM students';
$result = mysql_query($sql, $records);
echo "<table border='0' class='table table-striped table-bordered table-hover'>";
echo "<tr class='info'><td width='10%'>Name</td><td width='11%'>Course Yr-Sec</td><td width='10%'>Student Number</td><td width='10%'>Violation</td><td width='10%'>Punishment</td><td width='9%'>Violation Date</td><td width='7%'>Punishment Date</td><td width='5%'>CS Length</td><td width='4%'>CS Done</td><td width='4%'>CS Left</td><td width='17%'><center>Action</center></td></tr></tr>";

while($row = mysql_fetch_array($result))
{
echo "<tr>";
echo "<td>";
echo $row['Lastname'];
echo ", ";
echo $row['Firstname'];
echo " ";
echo $row['Middleinitial'];
echo "</td>";
echo "<td>";
echo $row['Course'];
echo " ";
echo $row['Year'];
echo "-";
echo $row['Section'];
echo "</td>";
echo "<td>";
echo $row['Studentnumber'];
echo "</td>";
echo "<td>";
echo $row['Violation'];
echo "</td>";
echo "<td>";
echo $row['Punishment'];
echo "</td>";
echo "<td>";
echo $row['Violationdate'];
echo "</td>";
echo "<td>";
echo $row['Punishmentstartdate'];
echo "</td>";
echo "<td>";
echo $row['CSlength'];
echo "</td>";
echo "<td>";
echo $row['CSDone'];
echo "</td>";
echo "<td>";
echo $row['CSLeft'];
echo "</td>";
echo "<td>";
echo "<a href='edit.php?no={$row['ID']}'><input type='button' name='edit' value='Edit' class='btn btn-success'></a>";
echo "   <a href='delete.php?no={$row['ID']}'><input type='button' name='delete' value='Delete' class='btn btn-danger'></a>";
echo "   <input type='button' name='view' value='View' class='btn btn-info'>";
echo "</td>";
echo "</tr>";
}
echo "</table>";
}
?>      

---

这是一个
左连接
。它将返回来自
students1
的所有记录，以及来自
students2
的任何记录，其中记录与
students1
中的记录具有相同的
studentnumber
：

SELECT * FROM students1
LEFT JOIN students2
ON students1.studentnumber = students2.studentnumber
AND students1.studentnumber = 20101000

内部联接
只返回产生匹配项的记录，因此只能在
students1
和
students2
中都有相同的
studentnumber
的记录。根据你的评论，我相信这就是你想要的风格：

SELECT * FROM students1
INNER JOIN students2
ON students1.studentnumber = students2.studentnumber
AND students1.studentnumber = 20101000

如果您想了解如何使用联接，我建议您尝试使用这两种语句来观察结果。然后尝试其他一些方法，可能使用。
请添加您的问题的表结构和要获取的预期列。可能重复Lastname（varchar）、Firstname（varchar）、Middleinitial（varchar）、Course（varchar）、Year（int）、Section（text）、Studentnumber（varchar）、Violationdate（varchar）、惩罚（varchar）、Violationdate（date）、惩罚StartDate（date）、CSlength（int）、ID（int、主键、自动递增）、CsOne（int）、CSLeft（int）…我想获取两个表中的所有列…假设另一个表没有第一个表所拥有的所有信息…@AbhikChakraborty。。。