显示值在 mysql 查询中是否唯一

Question

I have a MySQL query. In this query I want to make a column where I can show if the value in the column Phone is unique or not. How to do this?

This is the query:

SELECT ID, Phone
FROM tbltest

Answer 1

We can use COUNT() here as an analytic function:

SELECT ID, Phone,
       CASE WHEN COUNT(*) OVER (PARTITION BY Phone) = 1 THEN 'unique' END AS label
FROM tbltest
ORDER BY ID;

Here is a version which should work on earlier versions of MySQL:

SELECT t1.ID, t1.Phone,
       CASE WHEN t2.cnt = 1 THEN 'unique' END AS label
FROM tbltest t1
INNER JOIN
(
    SELECT Phone, COUNT(*) AS cnt
    FROM tbltest
    GROUP BY Phone
) t2
    ON t2.Phone = t1.Phone;

Answer 2

I tried the code on localhost with mysql 7.4.20 and the code works good. When I tried it on my productions server with mysql 5.6.45 the code didn't work. How to change the code that it is also working on mysql 5.6.45 ?