fix fk time issues

Author: elianddb

enginetest/queries/script_queries.go

@@ -10856,83 +10856,72 @@ where
 		},
 		Assertions: []ScriptTestAssertion{
 			{
-				Skip:  true,
 				Query: "create table child_datetime0 (dt datetime, foreign key (dt) references parent_datetime6(dt));",
 				Expected: []sql.Row{
 					{types.NewOkResult(0)},
 				},
 			},
 			{
-				Skip:        true,
 				Query:       "insert into child_datetime0 values ('2001-02-03 12:34:56');",
 				ExpectedErr: sql.ErrForeignKeyChildViolation,
 			},
 			{
-				Skip:  true,
 				Query: "create table child_datetime6 (dt datetime(6), foreign key (dt) references parent_datetime0(dt));",
 				Expected: []sql.Row{
 					{types.NewOkResult(0)},
 				},
 			},
 			{
-				Skip:        true,
 				Query:       "insert into child_datetime6 values ('2001-02-03 12:34:56');",
 				ExpectedErr: sql.ErrForeignKeyChildViolation,
 			},
 
 			{
-				Skip:  true,
 				Query: "create table child1_timestamp0 (ts timestamp, foreign key (ts) references parent_datetime0(dt));",
 				Expected: []sql.Row{
 					{types.NewOkResult(0)},
 				},
 			},
 			{
-				Skip:        true,
 				Query:       "insert into child1_timestamp0 values ('2001-02-03 12:34:56');",
 				ExpectedErr: sql.ErrForeignKeyChildViolation,
 			},
 			{
-				Skip:  true,
 				Query: "create table child2_timestamp0 (ts timestamp, foreign key (ts) references parent_datetime6(dt));",
 				Expected: []sql.Row{
 					{types.NewOkResult(0)},
 				},
 			},
 			{
-				Skip:        true,
 				Query:       "insert into child2_timestamp0 values ('2001-02-03 12:34:56');",
 				ExpectedErr: sql.ErrForeignKeyChildViolation,
 			},
 
 			{
-				Skip:  true,
 				Query: "create table child1_timestamp6 (ts timestamp(6), foreign key (ts) references parent_datetime0(dt));",
 				Expected: []sql.Row{
 					{types.NewOkResult(0)},
 				},
 			},
 			{
-				Skip:        true,
 				Query:       "insert into child1_timestamp6 values ('2001-02-03 12:34:56');",
 				ExpectedErr: sql.ErrForeignKeyChildViolation,
 			},
 			{
-				Skip:  true,
 				Query: "create table child2_timestamp6 (ts timestamp(6), foreign key (ts) references parent_datetime6(dt));",
 				Expected: []sql.Row{
 					{types.NewOkResult(0)},
 				},
 			},
 			{
-				Skip:        true,
 				Query:       "insert into child2_timestamp6 values ('2001-02-03 12:34:56');",
 				ExpectedErr: sql.ErrForeignKeyChildViolation,
 			},
 			{
-				Skip:        true,
-				Query:       "insert into child2_timestamp6 values ('2001-02-03 12:34:56.123456');",
-				ExpectedErr: sql.ErrForeignKeyChildViolation,
+				Query: "insert into child2_timestamp6 values ('2001-02-03 12:34:56.123456');",
+				Expected: []sql.Row{
+					{types.NewOkResult(1)},
+				},
 			},
 		},
 	},

sql/plan/alter_foreign_key.go

@@ -651,6 +651,16 @@ func foreignKeyComparableTypes(ctx *sql.Context, type1 sql.Type, type2 sql.Type)
 	t1 := type1.Type()
 	t2 := type2.Type()
 
+	// Handle time-related types with different precisions or cross-type references
+	if (types.IsTime(type1) || types.IsTimespan(type1)) && (types.IsTime(type2) || types.IsTimespan(type2)) {
+		// MySQL allows time-related types to reference each other in foreign keys:
+		// - DATETIME can reference DATETIME with different precision
+		// - TIMESTAMP can reference TIMESTAMP with different precision  
+		// - DATETIME can reference TIMESTAMP and vice versa
+		// - TIME can reference TIME with different precision
+		return true
+	}
+
 	// Handle same-type cases for special types
 	if t1 == t2 {
 		switch t1 {