reference: update the description of SQL_MODE and character sets

dev/reference/mysql-compatibility.md

@@ -25,7 +25,7 @@ However, TiDB does not support some of MySQL features or behaves differently fro
 + `FOREIGN KEY` constraints
 + `FULLTEXT` functions and indexes
 + `SPATIAL` functions and indexes
-+ Character sets other than `utf8mb4` and `utf8`
++ Character sets other than `utf8`, `utf8mb4`, `ascii`, `latin1` and `binary`
 + Collations other than `BINARY`
 + Add primary key
 + Drop primary key

dev/reference/sql/functions-and-operators/aggregate-group-by-functions.md

@@ -55,7 +55,7 @@ mysql> select a, b, sum(c) from t group by a;
 ERROR 1055 (42000): Expression #2 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'b' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by
 ```
 
-TiDB does not currently enable the [`ONLY_FULL_GROUP_BY`](/dev/reference/mysql-compatibility.md#default-differences) mode by default.
+TiDB currently enables the [`ONLY_FULL_GROUP_BY`](/dev/reference/mysql-compatibility.md#default-differences) mode by default.
 
 ### Differences from MySQL
 

v2.1/reference/mysql-compatibility.md

@@ -24,7 +24,7 @@ Currently TiDB Server advertises itself as MySQL 5.7 and works with most MySQL d
 + `FOREIGN KEY` constraints
 + `FULLTEXT` functions and indexes
 + `SPATIAL` functions and indexes
-+ Character sets other than `utf8`
++ Character sets other than `utf8`, `utf8mb4`, `ascii`, `latin1` and `binary`
 + Collations other than `BINARY`
 + Add primary key
 + Drop primary key

v2.1/reference/sql/functions-and-operators/aggregate-group-by-functions.md

@@ -55,7 +55,7 @@ mysql> select a, b, sum(c) from t group by a;
 ERROR 1055 (42000): Expression #2 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'b' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by
 ```
 
-TiDB does not currently enable the [`ONLY_FULL_GROUP_BY`](/v2.1/reference/mysql-compatibility.md#default-differences) mode by default.
+TiDB currently enables the [`ONLY_FULL_GROUP_BY`](/v2.1/reference/mysql-compatibility.md#default-differences) mode by default.
 
 ### Differences from MySQL
 

v3.0/reference/mysql-compatibility.md

@@ -25,7 +25,7 @@ However, TiDB does not support some of MySQL features or behaves differently fro
 + `FOREIGN KEY` constraints
 + `FULLTEXT` functions and indexes
 + `SPATIAL` functions and indexes
-+ Character sets other than `utf8mb4` and `utf8`
++ Character sets other than `utf8`, `utf8mb4`, `ascii`, `latin1` and `binary`
 + Collations other than `BINARY`
 + Add primary key
 + Drop primary key

v3.0/reference/sql/functions-and-operators/aggregate-group-by-functions.md

@@ -56,7 +56,7 @@ mysql> select a, b, sum(c) from t group by a;
 ERROR 1055 (42000): Expression #2 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'b' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by
 ```
 
-TiDB does not currently enable the [`ONLY_FULL_GROUP_BY`](/v3.0/reference/mysql-compatibility.md#default-differences) mode by default.
+TiDB currently enables the [`ONLY_FULL_GROUP_BY`](/v3.0/reference/mysql-compatibility.md#default-differences) mode by default.
 
 ### Differences from MySQL