[英]Two JOINS on same table
我在一個網站上工作,該網站在我的數據庫中顯示了兩支球隊的足球得分和兩分。
這是我的代碼:
<?php
$result = mysql_query( "SELECT * FROM resultat
LEFT JOIN brukere ON resultat.dommer = brukere.id
INNER JOIN lag ON resultat.lag1 = lag.id
INNER JOIN lag ON resultat.lag2 = lag.id
ORDER BY slutt DESC
" )
or die("SELECT Error: ".mysql_error());
$num_rows = mysql_num_rows($result);if ($result) {while ($row = mysql_fetch_array($result)) {
$_SESSION['id']=$row['id'];
?>
<tr>
<td><?php echo $row['klubb']; ?></td>
<td><?php echo $row['klubb']; ?></td>
<td><?php echo $row['stilling1'] . " - " . $row['stilling2']; ?></td>
<td><?php echo $row['roed'] . " rødt og " . $row['gult'] . " gult"; ?></td>
<td><?php echo $row['bane']; ?></td>
<td><?php echo $row['navn']; ?></td>
</tr>
<?php
}
}
?>
我得到:
選擇錯誤:不是唯一的表/別名:'滯后'
當我嘗試:
INNER JOIN lag s ON resultat.lag1 = lag.id
INNER JOIN lag c ON resultat.lag2 = lag.id
我得到:
SELECT錯誤:“ on子句”中的未知列“ lag.id”
我該怎么做? 來自同一表的兩個聯接
您需要使用剛賦予表lag
的別名。 您在第一次加入時分配了s
,在第二次加入時分配了c
,因此您應該使用它們
INNER JOIN lag s ON resultat.lag1 = s.id
INNER JOIN lag c ON resultat.lag2 = c.id
您可以嘗試將JOIN這樣合並:
INNER JOIN lag ON resultat.lag1 = lag.id OR resultat.lag2 = lag.id
如果需要,請用AND替換OR
這是一個自聯接,並且在expession中需要別名:
INNER JOIN lag s ON resultat.lag1 = s.id
INNER JOIN lag c ON resultat.lag2 = c.id
通常,您將自連接與鄰接列表一起使用,並將樹沿維度移動:
SELECT t1.name AS lev1, t2.name as lev2, t3.name as lev3, t4.name as lev4
FROM category AS t1
LEFT JOIN category AS t2 ON t2.parent = t1.category_id
LEFT JOIN category AS t3 ON t3.parent = t2.category_id
LEFT JOIN category AS t4 ON t4.parent = t3.category_id
WHERE t1.parent is NULL
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