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-- MySQL
SELECT
UNHEX(HEX(55)),
CONV(HEX('7'), 16, 10),
CONV(HEX(SUBSTRING('56789', 3, 1)), 16, 10)
/*
-- SQL Server
SELECT
CHAR(55),
ASCII('7'),
ASCII(SUBSTRING('56789', 3, 1))
*/
| UNHEX(HEX(55)) | CONV(HEX('7'), 16, 10) | CONV(HEX(SUBSTRING('56789', 3, 1)), 16, 10) |
|---|---|---|
| 7 | 55 | 55 |