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## SQL Server – How to convert hexadecimal to binary

How to convert hexadecimal to binary became very interesting when I was trying to read SQL Server log. Most part of SQL Server log data is in Hexadecimal so you need to convert it from hexadecimal to multiple formats to read it properly. Generally, programmers use the hexadecimal table to convert it into binary. But I developed this solution using remainder method and used it in almost all my solutions, wherever I used SQL Server log. Given below is the script.

Script :

```--DROP FUNCTION dbo.[UDF_Convert_Hex_to_Binary]
--GO
CREATE FUNCTION dbo.[UDF_Convert_Hex_to_Binary]
(
@HEX VARBINARY(MAX)
)
RETURNS VARCHAR(MAX)
BEGIN

DECLARE @BINARY VARCHAR(MAX)

;WITH N1 (n) AS (SELECT 1 UNION ALL SELECT 1),
N2 (n) AS (SELECT 1 FROM N1 AS X, N1 AS Y),
N3 (n) AS (SELECT 1 FROM N2 AS X, N2 AS Y),
N4 (n) AS (SELECT ROW_NUMBER() OVER(ORDER BY X.n)
FROM N3 AS X, N3 AS Y)

SELECT @BINARY=ISNULL(@BINARY,'')
+ CONVERT(NVARCHAR(1), (SUBSTRING(@HEX, Nums.n, 1) / 128) % 2)
+ CONVERT(NVARCHAR(1), (SUBSTRING(@HEX, Nums.n, 1) / 64) % 2)
+ CONVERT(NVARCHAR(1), (SUBSTRING(@HEX, Nums.n, 1) / 32) % 2)
+ CONVERT(NVARCHAR(1), (SUBSTRING(@HEX, Nums.n, 1) / 16) % 2)
+ CONVERT(NVARCHAR(1), (SUBSTRING(@HEX, Nums.n, 1) / 8) % 2)
+ CONVERT(NVARCHAR(1), (SUBSTRING(@HEX, Nums.n, 1) / 4) % 2)
+ CONVERT(NVARCHAR(1), (SUBSTRING(@HEX, Nums.n, 1) / 2) % 2)
+ CONVERT(NVARCHAR(1), SUBSTRING(@HEX, Nums.n, 1) % 2)

FROM N4 Nums
WHERE Nums.n<=LEN(@HEX)

RETURN @BINARY
END
GO
```

Example :

```Select dbo.[UDF_Convert_Hex_to_Binary](0x1cFEEE) AS [Hex to Binary]
GO
Select dbo.[UDF_Convert_Hex_to_Binary](0x2efd) AS [Hex to Binary]
GO
--OUTPUT
```