fix g4 for assignmentValueNode get error by index (#3290)

* fix 3279

* fix assigmentRight_

* adjust assignmentValue grammar

* add valuesFunction_ in expr

sharding-core/sharding-core-parse/sharding-core-parse-mysql/src/main/antlr4/imports/mysql/BaseRule.g4

@@ -377,7 +377,7 @@ frameBetween_
 
 specialFunction_
     : groupConcatFunction_ | windowFunction_ | castFunction_ | convertFunction_ | positionFunction_ | substringFunction_ | extractFunction_ 
-    | charFunction_ | trimFunction_ | weightStringFunction_
+    | charFunction_ | trimFunction_ | weightStringFunction_ | valuesFunction_
     ;
 
 groupConcatFunction_
@@ -417,6 +417,10 @@ trimFunction_
     : TRIM LP_ (LEADING | BOTH | TRAILING) STRING_ FROM STRING_ RP_
     ;
 
+valuesFunction_
+    : VALUES LP_ columnName RP_
+    ;
+
 weightStringFunction_
     : WEIGHT_STRING LP_ expr (AS dataType)? levelClause_? RP_
     ;

sharding-core/sharding-core-parse/sharding-core-parse-mysql/src/main/antlr4/imports/mysql/DMLStatement.g4

@@ -56,7 +56,7 @@ updateSpecification_
     ;
 
 assignment
-    : columnName EQ_ VALUES? LP_? assignmentValue RP_?
+    : columnName EQ_ assignmentValue
     ;
 
 setAssignmentsClause