[英]how to select two columns from two tables in mysql
我正在尝试执行此查询,但出现错误“未定义索引:lname”。我想从表a中的一个列(fname)中计算行,并从其他表b中选择列(lname)。 所以请帮我
$result = mysql_query("SELECT COUNT(fname),lname FROM a,b");
while ($row = mysql_fetch_array($result))
{
echo "<tr><td>";
echo $row['lname'];
echo "</td>";
echo "<td>";
echo $row['COUNT(fname)'];
echo "</td></tr>";
}
如果仍然出现错误,则可以尝试分别获取两者:
$result = mysql_query("SELECT COUNT(fname) FROM a");
while ($row = mysql_fetch_array($result))
{
echo "<tr><td>";
echo $row['COUNT(fname)'];
echo "</td></tr>";
}
$result1 = mysql_query("SELECT lname FROM b");
while ($row = mysql_fetch_array($result1))
{
echo "<tr><td>";
echo $row['lname'];
echo "</td></tr>";
}
您需要使用别名。 用这个:
$result = mysql_query("SELECT COUNT(fname) AS countfname,lname FROM a,b");
while ($row = mysql_fetch_array($result))
{
echo "<tr><td>";
echo $row['lname'];
echo "</td>";
echo "<td>";
echo $row['countfname'];
echo "</td></tr>";
}
试试这个代码:
$result = mysql_query("SELECT COUNT(a.fname) as fname,b.lname as lname FROM a,b");
while ($row = mysql_fetch_array($result))
{
echo "<tr><td>";
echo $row['lname'];
echo "</td>";
echo "<td>";
echo $row['COUNT(fname)'];
echo "</td></tr>";
}
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