When using SELECT can you modify the value of a returned field based on other fields?

Question

When using MySQL SELECT can you change the value of a returned field based on other fields?

For example, if I have this select:

SELECT city,state,cou         


        

Answer 1

Update(misprints corrected):

SELECT city,state,
CASE 
 WHEN (city IS NULL OR city='') AND (state IS NULL or state='') THEN ''
 ELSE country
END as country_1
 FROM `table`

You can also use IF instead of CASE:
IF ((city IS NULL OR city='') AND (state IS NULL or state=''),'',country) as country_1

Answer 2

The answer is yes; you're looking for what's called control flow functions.

Take a look at http://dev.mysql.com/doc/refman/5.0/en/control-flow-functions.html

Answer 3

Why don't you just use a WHERE clause?

For example:

SELECT city, state, country FROM <table> WHERE (city <> "" OR state <> "");

N.B.: You'll need to replace the '<> ""' above with 'IS NOT NULL' if these are actually nulled rather than simply empty.

Answer 4

a1ex07 is right, but you need to fix a few query errors in his SELECT stmt.

first, there is a missing comma after "state" and second, if your table were really called "table" you have to enclose in backticks because it is a reserved MySQL keyword.

SELECT city,state, 
CASE 
 WHEN (city IS NULL OR city='') AND (state IS NULL or state='') THEN ''
 ELSE country
END as country_1
 FROM `table`` 

(exlude second backtick, stackoverflow uses those for syntax highlighting if single.)