You can use
sys.sp_addextendedproperty
EXEC sys.sp_addextendedproperty
@name=N'MS_Description'
,@value=N'Here is my description!'
,@level0type=N'SCHEMA'
,@level0name=N'dbo'
,@level1type=N'TABLE'
,@level1name=N'TABLE_NAME'
,@level2type=N'COLUMN'
,@level2name=N'FIELD_NAME'
for more information look at this link:
http://technet.microsoft.com/en-us/library/ms180047.aspx[
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