先选择一行，然后再选择第二行

Question

我有以下问题：我的目标是一次得到两行。这是两次相同的“选择”语句，只是另一个ID。用我的代码，我只是得到第二行。怎样才能同时获得两条线？

select 
table1.attr1 + table2.attr2 as total, 
table1.id 
FROM table1, table2 
WHERE table.id = 1 AND table2.id = 1; 

select 
table1.attr1 + table2.attr2 as total, 
table1.id 
FROM table1, table2 
WHERE table.id = 2 AND table2.id = 2; 

Answer 1

使用明确joins与on条款：

select t1.attr1 + t2.attr2 as total 
    , t1.id 
FROM table1 t1 join table2 t2 on t1.id = t2.id 
WHERE t1.id in (1, 2) 

Answer 2

修改您的加盟条件：

SELECT 
    table1.attr1 + table2.attr2 as total, 
    table1.id 
FROM table1, table2 
WHERE (table.id = 1 AND table2.id = 1) 
    OR (table.id = 2 AND table2.id = 2)