SQL Server 2017

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CREATE TABLE TestTable (ID int IDENTITY(1,1),
                        SomeInt int,
                        SomeDecimal decimal(10,2),
                        SomeFloat float,
                        SomeMoney money,
                        SomeDate date,
                        SomeDatetime datetime,
                        SomeTime time,
                        SomeDatetime2 datetime2(1),
                        SomeVarbinary varbinary(12),
                        SomeVarchar varchar(10),
                        SomeBit bit);
INSERT INTO dbo.TestTable (SomeInt,
                           SomeDecimal,
                           SomeFloat,
                           SomeMoney,
                           SomeDate,
                           SomeDatetime,
                           SomeTime,
                           SomeDatetime2,
                           SomeVarbinary,
                           SomeVarchar,
                           SomeBit)
VALUES(NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL),
      (NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL);
2 rows affected

UPDATE dbo.TestTable
SET SomeInt = ISNULL(SomeInt,''),
    --SomeDecimal = ISNULL(SomeDecimal,''),
    SomeFloat = ISNULL(SomeFloat,''),
    SomeMoney = ISNULL(SomeMoney,''),
    SomeDate = ISNULL(SomeDate,''),
    SomeDatetime = ISNULL(SomeDatetime,''),
    SomeTime = ISNULL(SomeTime,''),
    SomeDatetime2 = ISNULL(SomeDatetime2,''),
    SomeVarbinary = ISNULL(SomeVarbinary,CONVERT(varbinary,'')),
    SomeVarchar = ISNULL(SomeVarchar,''),
    SomeBit = ISNULL(SomeBit,'')
WHERE ID = 1;
1 rows affected

DECLARE @Schema sysname = N'dbo',
        @Table sysname = N'TestTable';

DECLARE @SQL nvarchar(MAX);

SET @SQL = N'UPDATE ' + QUOTENAME(@Schema) + N'.' + QUOTENAME(@Table) + NCHAR(13) + NCHAR(10) +
           N'SET ' + STUFF((SELECT N',' + NCHAR(13) + NCHAR(10) + 
                                   N'    ' + QUOTENAME(C.COLUMN_NAME) + N' = ISNULL(' + QUOTENAME(C.COLUMN_NAME) + N',' + CASE C.DATA_TYPE WHEN N'decimal' THEN '0)'
                                                                                                                                           WHEN N'numeric' THEN '0)'
                                                                                                                                           ELSE N'CONVERT(' + QUOTENAME(C.DATA_TYPE) + N',N''''))'
                                                                                 END
                            FROM INFORMATION_SCHEMA.COLUMNS C
                            WHERE C.TABLE_SCHEMA = @Schema
                              AND C.TABLE_NAME = @Table
                              AND C.COLUMN_NAME != 'ID' --You'll need a better method to ignore your ID column
                            FOR XML PATH(N''),TYPE).value('.','nvarchar(MAX)'),1,7,N'') + NCHAR(13) + NCHAR(10) +
          N'WHERE ID = 2;'; --you won't want this if you're doing every row.

PRINT @SQL;

EXEC sp_executesql @SQL;
UPDATE [dbo].[TestTable]
SET [SomeInt] = ISNULL([SomeInt],CONVERT([int],N'')),
    [SomeDecimal] = ISNULL([SomeDecimal],0),
    [SomeFloat] = ISNULL([SomeFloat],CONVERT([float],N'')),
    [SomeMoney] = ISNULL([SomeMoney],CONVERT([money],N'')),
    [SomeDate] = ISNULL([SomeDate],CONVERT([date],N'')),
    [SomeDatetime] = ISNULL([SomeDatetime],CONVERT([datetime],N'')),
    [SomeTime] = ISNULL([SomeTime],CONVERT([time],N'')),
    [SomeDatetime2] = ISNULL([SomeDatetime2],CONVERT([datetime2],N'')),
    [SomeVarbinary] = ISNULL([SomeVarbinary],CONVERT([varbinary],N'')),
    [SomeVarchar] = ISNULL([SomeVarchar],CONVERT([varchar],N'')),
    [SomeBit] = ISNULL([SomeBit],CONVERT([bit],N''))
WHERE ID = 2;
1 rows affected

SELECT *
FROM dbo.TestTable;


ID
SomeInt
SomeDecimal
SomeFloat
SomeMoney
SomeDate
SomeDatetime
SomeTime
SomeDatetime2
SomeVarbinary
SomeVarchar
SomeBit


1
0
null
0
0.0000
01/01/1900 00:00:00
01/01/1900 00:00:00
00:00:00
01/01/1900 00:00:00
0x

False

2
0
0.00
0
0.0000
01/01/1900 00:00:00
01/01/1900 00:00:00
00:00:00
01/01/1900 00:00:00
0x

False
ID	SomeInt	SomeDecimal	SomeFloat	SomeMoney	SomeDate	SomeDatetime	SomeTime	SomeDatetime2	SomeVarbinary	SomeVarchar	SomeBit
1	0	null	0	0.0000	01/01/1900 00:00:00	01/01/1900 00:00:00	00:00:00	01/01/1900 00:00:00	0x		False
2	0	0.00	0	0.0000	01/01/1900 00:00:00	01/01/1900 00:00:00	00:00:00	01/01/1900 00:00:00	0x		False