fix some queries

Author: James Cor

enginetest/queries/script_queries.go

@@ -403,8 +403,8 @@ FROM task_instance INNER JOIN job ON job.id = task_instance.queued_by_job_id INN
 		},
 	},
 	{
-		Name:    "string to number comparison correctly truncates",
 		Dialect: "mysql",
+		Name:    "string to number comparison correctly truncates",
 		Assertions: []ScriptTestAssertion{
 			{
 				Query:                           "SELECT 'A' = 0;",
@@ -617,13 +617,12 @@ FROM task_instance INNER JOIN job ON job.id = task_instance.queued_by_job_id INN
 				Expected: []sql.Row{{true}},
 			},
 			{
-				// TODO: 123.456 is converted to a DECIMAL by Builder.ConvertVal, when it should be a DOUBLE
 				SkipResultCheckOnServerEngine:   true, // TODO: warnings do not make it to server engine
 				Query:                           "SELECT '123.456ABC' in (123.456);",
 				Expected:                        []sql.Row{{true}},
 				ExpectedWarningsCount:           1,
 				ExpectedWarning:                 mysql.ERTruncatedWrongValue,
-				ExpectedWarningMessageSubstring: "Truncated incorrect decimal(65,30) value: 123.456ABC",
+				ExpectedWarningMessageSubstring: "Truncated incorrect double value: 123.456ABC",
 			},
 			{
 				Query:    "SELECT '123.456e2' in (12345.6);",
@@ -7337,9 +7336,10 @@ CREATE TABLE tab3 (
 				},
 			},
 			{
-				// This actually matches MySQL behavior
-				Query:    "select * from t where (f in (null, 0.8));",
-				Expected: []sql.Row{},
+				Query: "select count(*) from t where (f in (null, 0.8));",
+				Expected: []sql.Row{
+					{1},
+				},
 			},
 			{
 				// select count to avoid floating point comparison

sql/expression/in.go

@@ -62,11 +62,17 @@ func NewInTuple(left sql.Expression, right sql.Expression) *InTuple {
 
 // validateAndEvalRightTuple will evaluate the right tuple, check if leftType and the right Tuple are comparable,
 // determine what type to use to compare the two sides, and indicate if right Tuple contains any NULL elements.
-// The NULL handling for IN expressions is tricky. According to
-// https://dev.mysql.com/doc/refman/8.0/en/comparison-operators.html#operator_in:
-// To comply with the SQL standard, IN() returns NULL not only if the expression on the left hand side is NULL, but
-// also if no match is found in the list and one of the expressions in the list is NULL.
+// Returns
+//   - slice of the evaluated elements
+//   - sql.Type to convert elements to before hashing
+//   - bool indicating if there are null elements
+//   - error
 func validateAndEvalRightTuple(ctx *sql.Context, lType sql.Type, right Tuple, row sql.Row) ([]any, sql.Type, bool, error) {
+	// The NULL handling for IN expressions is tricky. According to
+	// https://dev.mysql.com/doc/refman/8.0/en/comparison-operators.html#operator_in:
+	// To comply with the SQL standard, IN() returns NULL not only if the expression on the left hand side is NULL, but
+	// also if no match is found in the list and one of the expressions in the list is NULL.
+
 	// If left is StringType and ANY of the right is NumberType, then we should use Double Type for comparison
 	// If left is NumberType and ANT of the left is StringType, then we should use Double Type for comparison
 	lColCount := types.NumColumns(lType)
@@ -112,7 +118,10 @@ func validateAndEvalRightTuple(ctx *sql.Context, lType sql.Type, right Tuple, ro
 	} else if types.IsEnum(lType) || types.IsSet(lType) || types.IsText(lType) {
 		cmpType = lType
 	} else {
-		cmpType = types.GetCompareType(lType, right[0].Type())
+		cmpType = lType
+		for _, el := range right {
+			cmpType = types.GetCompareType(cmpType, el.Type())
+		}
 	}
 
 	return rVals, cmpType, rHasNull, nil
@@ -240,6 +249,11 @@ func NewHashInTuple(ctx *sql.Context, left, right sql.Expression) (*HashInTuple,
 }
 
 // newInMap hashes static expressions in the right child Tuple of a InTuple node
+// returns
+//   - map of the hashed elements
+//   - sql.Type to convert elements to before hashing
+//   - bool indicating if there are null elements
+//   - error
 func newInMap(ctx *sql.Context, lType sql.Type, right Tuple) (map[uint64]struct{}, sql.Type, bool, error) {
 	if lType == types.Null {
 		return nil, nil, true, nil