sp_addextendedproperty (Transact-SQL MetaData) Definition

Please note: that the following source code is provided and copyrighted by Microsoft and is for educational purpose only.
The meta data is from an SQL 2012 Server.

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Definition:

sys.sp_addextendedproperty(nvarchar @name
, sql_variant @value
, varchar @level0type
, nvarchar @level0name
, varchar @level1type
, nvarchar @level1name
, varchar @level2type
, nvarchar @level2name)

MetaData:

 create procedure sys.sp_addextendedproperty  
    @name sysname,  
    @value sql_variant            = NULL,  
    @level0type    varchar(128)    = NULL,  
    @level0name    sysname            = NULL,  
    @level1type    varchar(128)    = NULL,  
    @level1name    sysname            = NULL,  
    @level2type    varchar(128)    = NULL,  
    @level2name    sysname            = NULL  
as  
  
    declare @ret int  
  
    if datalength(@value) > 7500  
    begin  
        raiserror(15097,-1,-1)  
        return 1  
    end  
      
    if @name is null  
    begin  
        raiserror(15600,-1,-1,'sp_addextendedproperty')  
        return (1)  
    end  
  
    execute @ret = sys.sp_validname @name  
    if (@ret <> 0)  
    begin  
        raiserror(15600,-1,-1,'sp_addextendedproperty')  
        return (1)  
    end  
          
  
    BEGIN TRANSACTION  
      
    begin  
        EXEC %%ExtendedPropertySet().AddValue(Name = @name, Value = @value, Level0type = @level0type, Level0name = @level0name, Level1type = @level1type, Level1name = @level1name, Level2type = @level2type, Level2name = @level2name)  
        IF @@error <> 0  
        begin  
            COMMIT TRANSACTION  
            return (1)  
        end  
    end  
      
    COMMIT TRANSACTION  
    return (0)