oracle 如何使用连接'||' 带有 SELECT 查询的不同子句？
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How to use concatenation '||' with distinct clause of SELECT query?
提问by cctk11
I get a missing expression error when I try,
当我尝试时，我得到一个缺少表达式的错误，
SELECT 'label1:'||distinct col1 from tab1;
Is there a way to get around this error? Thanks in advance.
有没有办法解决这个错误？提前致谢。
Edit: The entire query is:
编辑：整个查询是：
SELECT 'label1:'||distinct col1 from tab1 order by col1;
采纳答案by Bharat
try this one
试试这个
SELECT DISTINCT 'label1:' || col1
FROM tab1 order by 1;
回答by Martin Smith
The first error is because distinctis in the wrong place.
第一个错误是因为distinct在错误的地方。
SELECT distinct 'label1:'|| col1 as c
from tab1
ORDER BY c;
The second one mentioned in the comments is because you were ordering by col1. You need to alias the new column and order by the alias as above. (Note you can use col1as the alias if you want)
评论中提到的第二个是因为您是按 col1 订购的。您需要为新列添加别名并按上述别名排序。（请注意col1，如果需要，您可以将其用作别名）
回答by Quassnoi
DISTINCTis a part of a SELECTclause, not the function of the columns:
DISTINCT是SELECT子句的一部分，而不是列的功能：
SELECT DISTINCT 'label1:' || col1
FROM tab1
Update:
更新：
To make it work with ORDER BY, use
要使其与 一起ORDER BY使用，请使用
SELECT 'label1:' || col1
FROM (
SELECT DISTINCT col1
FROM tab1
)
ORDER BY
col1
