fix: mssql uses unsigned for tinyint instead of signed

sqlx-core/src/mssql/types/mod.rs

@@ -6,6 +6,7 @@ mod bool;
 mod float;
 mod int;
 mod str;
+mod uint;
 
 impl<'q, T: 'q + Encode<'q, Mssql>> Encode<'q, Mssql> for Option<T> {
     fn encode(self, buf: &mut Vec<u8>) -> IsNull {

sqlx-core/src/mssql/types/uint.rs

@@ -0,0 +1,30 @@
+use crate::decode::Decode;
+use crate::encode::{Encode, IsNull};
+use crate::error::BoxDynError;
+use crate::mssql::protocol::type_info::{DataType, TypeInfo};
+use crate::mssql::{Mssql, MssqlTypeInfo, MssqlValueRef};
+use crate::types::Type;
+
+impl Type<Mssql> for u8 {
+    fn type_info() -> MssqlTypeInfo {
+        MssqlTypeInfo(TypeInfo::new(DataType::IntN, 1))
+    }
+
+    fn compatible(ty: &MssqlTypeInfo) -> bool {
+        matches!(ty.0.ty, DataType::TinyInt | DataType::IntN) && ty.0.size == 1
+    }
+}
+
+impl Encode<'_, Mssql> for u8 {
+    fn encode_by_ref(&self, buf: &mut Vec<u8>) -> IsNull {
+        buf.extend(&self.to_le_bytes());
+
+        IsNull::No
+    }
+}
+
+impl Decode<'_, Mssql> for u8 {
+    fn decode(value: MssqlValueRef<'_>) -> Result<Self, BoxDynError> {
+        Ok(value.as_bytes()?[0] as u8)
+    }
+}

tests/mssql/types.rs

@@ -5,6 +5,13 @@ test_type!(null<Option<i32>>(Mssql,
     "CAST(NULL as INT)" == None::<i32>
 ));
 
+test_type!(u8(
+    Mssql,
+    "CAST(5 AS TINYINT)" == 5_u8,
+    "CAST(0 AS TINYINT)" == 0_u8,
+    "CAST(255 AS TINYINT)" == 255_u8,
+));
+
 test_type!(i8(
     Mssql,
     "CAST(5 AS TINYINT)" == 5_i8,