Question

I have a table named A:

DATETIME_START || DATETIME_END || VALUE 
 --------------------------------------- 
2012-07-23     || 2013-07-23   ||  coffee  
2011-13-11     || 2013-01-09   ||  airport

all I am trying to do is – if the time of request is between DATETIME_START and DATETIME_END, simply return VALUE.

I tried:

SELECT 
IF (NOW() BETWEEN A.DATETIME_START AND A.DATETIME_END, VALUE,NULL)
FROM A

but what happens is that I get the string "IF (NOW() BETWEEN A.DATETIME_START AND A.DATETIME_END, VALUE,NULL)" in the result!

(I don’t want to put the condition in the WHERE)

Why is that?

Answer 1

The column name will be whatever you actually select. Say your select had looked like this instead:

SELECT
    IF (NOW() BETWEEN A.DATETIME_START AND A.DATETIME_END, ColumnA, ColumnB)

What should the resultset column name be when you are potentially getting results from 2 columns?

You may not even be selecting from any columns:

SELECT
    IF(0 < 1, 'True', 'False')

In your particular case you didn’t really need an IF statement, but when you do have e.g. conditions or functions in your SELECT, you can use
Alias
to determine the column name yourself.

SELECT
    IF(0 < 1, 'True', 'False') AS YourName
  # or
    IF(0 < 1, 'True', 'False') AS `Your name with spaces`