如何在MySQL中使用case语句将3列数据合并为一个

Question

I have a table with firstname, middlename, lastname. I want to add these 3 column data into one as fullname as if middlename != '' then fullname = firstname middlename and if lastname != '' then fullname = firstname middlename lastname. I tried as follows but no row is affected.

UPDATE studentprofiles SET fullname = CASE middlename WHEN middlename !=  '' THEN firstname +  ' ' + middlename ELSE firstname END WHERE fullname = ''

How to do this? I have to update multiple rows. Any help/suggestions are welcome.

Answer 1

Have you tried using an AND like this:

CASE
WHEN middlename != '' AND lastname != '' THEN firstname + middlename + lastname
ELSE ''
END AS fullname

Answer 2

The problem is solved as follows:

UPDATE studentprofiles 
    SET fullname = CASE
                WHEN middlename != '' AND lastname != '' THEN concat(firstname,' ',middlename,' ',lastname)
                WHEN middlename != '' AND lastname = '' THEN concat(firstname,' ',middlename)
                WHEN middlename = '' AND lastname != '' THEN concat(firstname,' ',lastname)
                ELSE concat(firstname)
END

Answer 3

Why can't you simply concatenate the columns data like

UPDATE studentprofiles 
SET fullname = concat(firstname, middlename, lastname);

EDIT: In that case you can use IFNULL() function like

UPDATE studentprofiles 
SET fullname = IFNULL(firstname,'') +
               IFNULL(middlename, '') +
               IFNULL(lastname, '');

Answer 4

try to use this :

CASE case_value
    WHEN when_value THEN statement_list
    [WHEN when_value THEN statement_list] ...
    [ELSE statement_list]
END CASE

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