If I have a table such as
如果我有一张桌子如
1 bob
1 ray
1 bob
1 ray
2 joe
2 joe
And I want to select distinct based on the two columns so that I would get
我想根据两列选择不同的，以便我得到
1 bob
1 ray
2 joe
How can I word my query? Is the only way to concatenate the columns and wrap them around a distinct function operator?
我该如何说出我的查询？是连接列并将它们包装在一个独特的函数运算符周围的唯一方法吗？
2 个解决方案
#1
25
select distinct id, name from [table]
or
要么
select id, name from [table] group by id, name
#2
5
You can just do:
你可以这样做：
select distinct col1, col2 from your_table;
That's exactly what the distinct operator is for: removing duplicate result rows.
这正是独特运算符的用途：删除重复的结果行。
Keep in mind that distinct is usually a pretty expensive operation, since, after processing the query, the DB server might perform a sort operation in order to remove the duplicates.
请记住，distinct通常是一个相当昂贵的操作，因为在处理查询之后，DB服务器可能会执行排序操作以删除重复项。
#1
25
select distinct id, name from [table]
or
要么
select id, name from [table] group by id, name
#2
5
You can just do:
你可以这样做：
select distinct col1, col2 from your_table;
That's exactly what the distinct operator is for: removing duplicate result rows.
这正是独特运算符的用途：删除重复的结果行。
Keep in mind that distinct is usually a pretty expensive operation, since, after processing the query, the DB server might perform a sort operation in order to remove the duplicates.
请记住，distinct通常是一个相当昂贵的操作，因为在处理查询之后，DB服务器可能会执行排序操作以删除重复项。