[MSSQL] Convert decimal to hexadecimal, hexadecimal to decimal ( Big Int )

1. Convert decimal to hexadecimal ( decimal data type: bigint )

SELECT CONVERT(VARCHAR(16),CONVERT(VARBINARY(8), CONVERT(BIGINT, 9223372036854775807 )),2) AS DEC2HEX

2. Convert hexadecimal to decimal ( decimal data type: bigint )

SELECT CONVERT(BIGINT,CONVERT(VARBINARY(8),'7FFFFFFFFFFFFFFF',2))  AS HEX2DEC