[英]mysql_num_rows from multiple tables
我想計算5個表格中的字段數量並顯示結果。 我目前只在一張桌子上做
$variable = mysql_num_rows(mysql_query("SELECT id FROM table1"));
什么是最有效的辦法,包括和計算所有id
從table2
, table3
, table4
和table5
?
謝謝
使用UNION ALL
組合所有表上的SELECT
查詢,以獲取所有表中ID的總數。 請改用UNION
從所有表中獲取distinct
ID的總數。
$variable = mysql_num_rows(mysql_query("
"SELECT id FROM table1 " .
"UNION ALL " .
"SELECT id FROM table2 " .
"UNION ALL " .
"SELECT id FROM table3 " .
"UNION ALL " .
"SELECT id FROM table4 " .
"UNION ALL " .
"SELECT id FROM table5"));
不要從數據庫中獲取所有行,只需獲取id的數量即可。 讓MySQL代替PHP計數。
$variable1 = mysql_query("SELECT COUNT(id) FROM table1");
$variable2 = mysql_query("SELECT COUNT(id) FROM table2");
$variable3 = mysql_query("SELECT COUNT(id) FROM table3");
$variable4 = mysql_query("SELECT COUNT(id) FROM table4");
$variable5 = mysql_query("SELECT COUNT(id) FROM table5");
$variable = $variable1 + $variable2 + $variable3 + $variable4 +$variable5;
不要創建UNION或JOIN,如果您只需要計數,這是一項繁重的工作。
SELECT count(t1.id)+count(t2.id)+count(t3.id)+count(t4.id)+count(t5.id) from table1 as t1, table2 as t2, table3 as t3, table4 as t4, table5 as t5
SELECT COUNT(id) FROM table2
等等
嘗試這樣的聯合語法:
$variable = mysql_num_rows(mysql_query("
SELECT * FROM(
SELECT id FROM table1
UNION
SELECT id FROM table2
UNION
SELECT id FROM table3
UNION
SELECT id FROM table4
UNION
SELECT id FROM table5
)unionNum
"));
完成,祝你好運
第一種方法:
$query = mysql_query("
select * from(
SELECT id FROM table1
union
SELECT id FROM table2
union
SELECT id FROM table3
union
SELECT id FROM table4
)
");
while ($row = mysql_fetch_assoc($query)) {
//some operations
}
$variable = mysql_num_rows($query);
第二種方法:
$query = mysql_query("
select count(*) cnt from(
SELECT id FROM table1
union
SELECT id FROM table2
union
SELECT id FROM table3
union
SELECT id FROM table4
)
");
while ($row = mysql_fetch_assoc($query)) {
$variable = $query['cnt'];
}
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