本文介绍了将 2 个 SQL SELECT 结果集合并为一个的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我有 2 个选择语句,返回的数据如下:
I've got 2 select statements, returning data like this:
Select 1 col_a col_b Select 2 col_a col_c如果我做联合,我会得到类似的东西
If I do union, I get something like
col_a col_b并且行加入.我需要的是这样:
And rows joined. What i need is getting it like this:
col_a col_b col_c加入 col_a
推荐答案使用 JOIN 连接子查询并使用 ON 表示每个子查询中的行必须匹配的位置:
Use JOIN to join the subqueries and use ON to say where the rows from each subquery must match:
SELECT T1.col_a, T1.col_b, T2.col_c FROM (SELECT col_a, col_b, ...etc...) AS T1 JOIN (SELECT col_a, col_c, ...etc...) AS T2 ON T1.col_a = T2.col_a如果 col_a 的某些值在 T1 中但不在 T2 中,则可以使用 LEFT OUTER JOIN 代替.
If there are some values of col_a that are in T1 but not in T2, you can use a LEFT OUTER JOIN instead.
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将 2 个 SQL SELECT 结果集合并为一个
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