improved PageUtils & support natural join. issue #1711

src/main/java/com/alibaba/druid/sql/PagerUtils.java

@@ -572,8 +572,14 @@ public class PagerUtils {
                     if (parent instanceof SQLSelectQuery) {
                         if (parent instanceof OracleSelectQueryBlock) {
                             OracleSelectQueryBlock queryBlock = (OracleSelectQueryBlock) parent;
-                            if (queryBlock.getFrom() instanceof SQLExprTableSource) {
+                            SQLTableSource from = queryBlock.getFrom();
+                            if (from instanceof SQLExprTableSource) {
                                 selectQuery = queryBlock;
+                            } else if (from instanceof SQLSubqueryTableSource) {
+                                SQLSelect subSelect = ((SQLSubqueryTableSource) from).getSelect();
+                                if (subSelect.getQuery() instanceof OracleSelectQueryBlock) {
+                                    selectQuery = (OracleSelectQueryBlock) subSelect.getQuery();
+                                }
                             }
                         }
                         break;
@@ -581,6 +587,7 @@ public class PagerUtils {
                 }
             }
 
+
             if (selectQuery != null) {
                 SQLObject parent = selectQuery.getParent();
                 if (parent instanceof SQLSelect) {

src/main/java/com/alibaba/druid/sql/ast/statement/SQLJoinTableSource.java

@@ -29,6 +29,9 @@ public class SQLJoinTableSource extends SQLTableSourceImpl {
     protected SQLExpr             condition;
     protected final List<SQLExpr> using = new ArrayList<SQLExpr>();
 
+
+    protected boolean             natural = false;
+
     public SQLJoinTableSource(String alias){
         super(alias);
     }
@@ -93,6 +96,14 @@ public class SQLJoinTableSource extends SQLTableSourceImpl {
         return this.using;
     }
 
+    public boolean isNatural() {
+        return natural;
+    }
+
+    public void setNatural(boolean natural) {
+        this.natural = natural;
+    }
+
     public void output(StringBuffer buf) {
         this.left.output(buf);
         buf.append(' ');

src/main/java/com/alibaba/druid/sql/parser/SQLSelectParser.java

@@ -458,6 +458,12 @@ public class SQLSelectParser extends SQLParser {
 
         SQLJoinTableSource.JoinType joinType = null;
 
+        boolean natural = false;
+        if (JdbcConstants.MYSQL.equals(dbType) && identifierEquals("NATURAL")) {
+            lexer.nextToken();
+            natural = true;
+        }
+
         if (lexer.token() == Token.LEFT) {
             lexer.nextToken();
             if (lexer.token() == Token.OUTER) {
@@ -516,6 +522,14 @@ public class SQLSelectParser extends SQLParser {
             join.setJoinType(joinType);
             join.setRight(parseTableSource());
 
+            if (!natural) {
+                if (JdbcConstants.MYSQL.equals(dbType) && "NATURAL".equalsIgnoreCase(tableSource.getAlias())) {
+                    tableSource.setAlias(null);
+                    natural = true;
+                }
+            }
+            join.setNatural(natural);
+
             if (lexer.token() == Token.ON) {
                 lexer.nextToken();
                 join.setCondition(expr());

src/main/java/com/alibaba/druid/sql/visitor/SQLASTOutputVisitor.java

@@ -1856,6 +1856,11 @@ public class SQLASTOutputVisitor extends SQLASTVisitorAdapter implements Paramet
             print(',');
         } else {
             println();
+
+            if (x.isNatural()) {
+                print0(ucase ? "NATURAL " : "natural ");
+            }
+
             printJoinType(x.getJoinType());
         }
         print(' ');