PHP SQL合併2查詢

Question

我有兩個疑問一個接直另：

$sql_result8 = mysql_query("SELECT * FROM properties WHERE c4='$id'", $db); $charges = mysql_num_rows($sql_result8); 
$sql_result8 = mysql_query("SELECT * FROM vehicles WHERE c4='$id'", $db); $charges = $charges + mysql_num_rows($sql_result8); 

我需要什麼樣的查詢合併這些？某種JOIN？聯盟？

Answer 1

SELECT * FROM properties p, vehicles v WHERE p.c4 = v.c4 AND p.c4 = '$id' 

Answer 2

試試這個

SELECT * FROM properties JOIN vehicles USING (c4) WHERE c4='$id' 

Answer 3

如果你只想找出行數從兩個查詢返回，而不是顯示實際列，您可以使用此：

$sql_result8 = mysql_query(
    "SELECT 
     (SELECT COUNT(*) FROM properties WHERE c4='$id') 
     + (SELECT COUNT(*) FROM vehicles WHERE c4='$id') 
    ", $db);