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Question 22: What will the following query return? – MySQL Question of the Day

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Question 22: What will the following query return?

18. February 2010
By urs in mysql questions

1 Comment

 

create table mintst (n int not null default 0);
 
select min(n),max(n) from mintst;
 
a) 0, 0
b) 0, 255
c) NULL, NULL
d) 0, NULL

 
[ SQL Expressions (15%) - NULL Values ]
 

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One Response

  1. urs — 18. February 2010 @ 19:20:12 —


     
    Answer:
     
    c
     
    The MIN/MAX values for an empty table are undefined and therefore NULL. I’ve seen statistics and reporting software abort because of empty tables ;-) You can use COALESCE() or IFNULL() to catch those NULL-values.
     
    mysql> select min(n),max(n) from mintst;
    +--------+--------+
    | min(n) | max(n) |
    +--------+--------+
    | NULL | NULL |
    +--------+--------+
    1 row in set (0.00 sec)
     

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