Where condition is null(coloumn name, 0) - ?

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SQL

select * from tbl_name
where ISNULL(ID,0) = xxx

Here in above statement ,

if xxx = 0 then what is ISNULL(ID,0)
if xxx = 1 then what is ISNULL(ID,0)
if xxx = 122 then what is ISNULL(ID,0)

how does ISNULL(ID,0) works in where condition

Posted 23-Nov-14 15:21pm

anbujeremiah

Updated 23-Nov-14 16:12pm

PIEBALDconsult

v2

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/\jmot · Answer 1 · 2014-11-23T18:24:00

SQL

isnull Replaces NULL with the specified replacement value.

SQL

ISNULL(ID,x) replaces all the null value of ID with x
where x= has a value.

SQL

where Id=0(without isnull check) means it'll skip all the ID containing the null value in the table.
and there is another problem that there are some datatype that are not comparable with the null value so in that case you can get the comparison error.
so, using isnull(ID,0) is used to set all the null value of ID by 0 and then coparing to the condition value(xxx).

for more info check this..
http://msdn.microsoft.com/en-us/library/ms184325.aspx[^]

DamithSL · Answer 2 · 2014-11-23T15:45:00

Solution 1

ISNULL(ID,0) will return zero if the ID column is null, otherwise it returns ID column value, So:

SQL

if xxx = 0  -- give you 0
if xxx = 1  -- give you 1
if xxx = 122 -- give you 122

Posted 23-Nov-14 15:45pm

DamithSL