如何使用sql语句获得想要的结果？

Question

I have some data in my database. I tried to do a retrieval and it should appear in such a way.

Current table:

FName| lName | phoneNo | year
Tom  | Tan   | 9123456 | 1  
Tom  | Tan   | 9012345 | 1 <----extra row

What I want:

FName | lName| phoneNo| year | phoneNo2
Tom   | Tan  | 9123456| 1    |9012345

How can I achieve this using sql statement?

I would like to see if FName and lName are duplicated, then the duplicated data will be combined as such the phoneNo will be added into one column called phoneNo2.

Answer 1

Do a GROUP BY , use MIN() to get first phoneno and MAX() to get the second.

select FName, lName, min(phoneNo), max(year), max(phoneNo)
from tablename
group by FName, lName

You can also do a self LEFT JOIN :

select t1.FName, t1.lName, t1.phoneNo, t1.year, t2.phoneNo
from tablename t1
left join tablename t2
    on t1.FName = t2.FName and t1.lName = t2.lName
    and t1.phoneNo < t2.phoneNo

Note: According to ANSI SQL YEAR is a reserved word, so you may need to delimit it as "year" .

Answer 2

Another option which will cope with more than 2 phone numbers is to use GROUP_CONCAT

SELECT FName, 
    lName,
    SUBSTRING_INDEX(GROUP_CONCAT(phoneNo), ',', 1) AS phoneNo, 
    `year`, 
    IF(COUNT(phoneNo) >= 2, SUBSTRING_INDEX(SUBSTRING_INDEX(GROUP_CONCAT(phoneNo), ',', 2), ',', -1), NULL) AS phoneNo2, 
    IF(COUNT(phoneNo) >= 3, SUBSTRING_INDEX(SUBSTRING_INDEX(GROUP_CONCAT(phoneNo), ',', 3), ',', -1), NULL) AS phoneNo3, 
    IF(COUNT(phoneNo) >= 4, SUBSTRING_INDEX(SUBSTRING_INDEX(GROUP_CONCAT(phoneNo), ',', 4), ',', -1), NULL) AS phoneNo4, 
    IF(COUNT(phoneNo) >= 5, SUBSTRING_INDEX(SUBSTRING_INDEX(GROUP_CONCAT(phoneNo), ',', 5), ',', -1), NULL) AS phoneNo5 
FROM tablename
GROUP BY FName, 
        lName,
        `year`