improve wall filter

src/main/java/com/alibaba/druid/sql/dialect/mysql/ast/statement/MySqlDeleteStatement.java

@@ -89,6 +89,9 @@ public class MySqlDeleteStatement extends SQLDeleteStatement {
     }
 
     public void setLimit(Limit limit) {
+        if (limit != null) {
+            limit.setParent(this);
+        }
         this.limit = limit;
     }
 

src/main/java/com/alibaba/druid/sql/dialect/mysql/ast/statement/MySqlSelectQueryBlock.java

@@ -165,6 +165,9 @@ public class MySqlSelectQueryBlock extends SQLSelectQueryBlock implements MySqlO
     }
 
     public void setLimit(Limit limit) {
+        if (limit != null) {
+            limit.setParent(this);
+        }
         this.limit = limit;
     }
 

src/main/java/com/alibaba/druid/sql/dialect/mysql/ast/statement/MySqlShowBinLogEventsStatement.java

@@ -57,6 +57,9 @@ public class MySqlShowBinLogEventsStatement extends MySqlStatementImpl implement
     }
 
     public void setLimit(Limit limit) {
+        if (limit != null) {
+            limit.setParent(this);
+        }
         this.limit = limit;
     }
 

src/main/java/com/alibaba/druid/sql/dialect/mysql/ast/statement/MySqlUnionQuery.java

@@ -32,6 +32,9 @@ public class MySqlUnionQuery extends SQLUnionQuery implements MySqlObject {
     }
 
     public void setLimit(Limit limit) {
+        if (limit != null) {
+            limit.setParent(this);
+        }
         this.limit = limit;
     }
 

src/main/java/com/alibaba/druid/sql/dialect/mysql/ast/statement/MySqlUpdateStatement.java

@@ -35,6 +35,9 @@ public class MySqlUpdateStatement extends SQLUpdateStatement implements MySqlSta
     }
 
     public void setLimit(Limit limit) {
+        if (limit != null) {
+            limit.setParent(this);
+        }
         this.limit = limit;
     }
 

src/main/java/com/alibaba/druid/sql/dialect/mysql/parser/MySqlExprParser.java

@@ -299,7 +299,7 @@ public class MySqlExprParser extends SQLExprParser {
                 }
 
                 String unitVal = lexer.stringVal();
-                MySqlIntervalUnit unit = MySqlIntervalUnit.valueOf(unitVal);
+                MySqlIntervalUnit unit = MySqlIntervalUnit.valueOf(unitVal.toUpperCase());
                 lexer.nextToken();
 
                 accept(Token.FROM);

src/main/java/com/alibaba/druid/sql/dialect/mysql/parser/MySqlStatementParser.java

@@ -640,6 +640,10 @@ public class MySqlStatementParser extends SQLStatementParser {
 
     public SQLStatement parseShow() {
         acceptIdentifier("SHOW");
+        
+        if (lexer.token() == Token.COMMENT) {
+            lexer.nextToken();
+        }
 
         boolean full = false;
         if (lexer.token() == Token.FULL) {
@@ -1508,6 +1512,10 @@ public class MySqlStatementParser extends SQLStatementParser {
         MySqlReplaceStatement stmt = new MySqlReplaceStatement();
 
         acceptIdentifier(REPLACE);
+        
+        if (lexer.token() == Token.COMMENT) {
+            lexer.nextToken();
+        }
 
         if (identifierEquals(LOW_PRIORITY)) {
             stmt.setLowPriority(true);