通過子查詢算術？

Question

你如何合併這兩行？

"SELECT col1, col2, col3, col4 FROM table_a WHERE col4 = '$col4_val'" 

和

"SELECT col1 FROM table_a WHERE col5 = '$col4_val'" 

說第一個查詢COL1 = 20，第二個查詢COL1 = 10

如何創建一個返回COL1，COL2，COL3的值的查詢， col1來自第一個查詢但col1 = 30（第一個和第二個查詢加在一起）？

我可以通過PHP做算術，但我寧願如果可能的話做查詢。

Answer 1

"SELECT (a.col1 + b.col1) as 'summed value', a.col2, a.col3, a.col4 
FROM table_a as a 
JOIN table_b as b 
ON a.col4 = b.col5 
WHERE a.col4 = '$col4_val'" 

Answer 2

OK沒關係我想通了..

"SELECT sum(col1 + (SELECT col1 FROM table_b WHERE col5 = '$col4_val')) as col1, col2, col3, col4 FROM table_a WHERE col4 = '$col4_val'"