“ISnull” field in Mysql database table showing as Zero for a single record. Why?

By | May 19, 2014

Present scenario::
In an already existing table we added a new field with data type tinyint with default as null

Age- varchar-250
testid-tinyint-default-null-yes (newly added field)

After creating the new field entire table data with testid as ‘NULL’

and once i did update on a particular record through query testid

updated to ‘0’

why it is coming like,means after updation field as 0 instead of null any solutions for this