Add FROM-first query syntax support

iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/relational/sql/parser/AstBuilder.java

@@ -2391,6 +2391,45 @@ public Node visitQuerySpecification(RelationalSqlParser.QuerySpecificationContex
         Optional.empty());
   }
 
+  @Override
+  public Node visitFromFirstQuerySpecification(
+      RelationalSqlParser.FromFirstQuerySpecificationContext ctx) {
+    Optional<Relation> from = Optional.empty();
+    List<SelectItem> selectItems = visit(ctx.selectItem(), SelectItem.class);
+
+    List<Relation> relations = visit(ctx.relation(), Relation.class);
+    if (!relations.isEmpty()) {
+      // synthesize implicit join nodes
+      Iterator<Relation> iterator = relations.iterator();
+      Relation relation = iterator.next();
+
+      while (iterator.hasNext()) {
+        relation = new Join(getLocation(ctx), Join.Type.IMPLICIT, relation, iterator.next());
+      }
+
+      from = Optional.of(relation);
+    }
+    if (selectItems.isEmpty()) {
+      selectItems = ImmutableList.of(new AllColumns(getLocation(ctx), ImmutableList.of()));
+    }
+
+    NodeLocation selectLocation =
+        ctx.SELECT() != null ? getLocation(ctx.SELECT()) : getLocation(ctx);
+
+    return new QuerySpecification(
+        getLocation(ctx),
+        new Select(selectLocation, isDistinct(ctx.setQuantifier()), selectItems),
+        from,
+        visitIfPresent(ctx.where, Expression.class),
+        visitIfPresent(ctx.groupBy(), GroupBy.class),
+        visitIfPresent(ctx.having, Expression.class),
+        Optional.empty(),
+        visit(ctx.windowDefinition(), WindowDefinition.class),
+        Optional.empty(),
+        Optional.empty(),
+        Optional.empty());
+  }
+
   @Override
   public Node visitSelectSingle(RelationalSqlParser.SelectSingleContext ctx) {
     if (ctx.identifier() != null) {

iotdb-core/relational-grammar/src/main/antlr4/org/apache/iotdb/db/relational/grammar/sql/RelationalSql.g4

@@ -996,6 +996,7 @@ queryPrimary
     | TABLE qualifiedName                  #table
     | VALUES expression (',' expression)*  #inlineTable
     | '(' queryNoWith ')'                  #subquery
+    | fromFirstQuerySpecification          #fromFirstQueryPrimary
     ;
 
 sortItem
@@ -1011,6 +1012,15 @@ querySpecification
       (WINDOW windowDefinition (',' windowDefinition)*)?
     ;
 
+fromFirstQuerySpecification
+    : FROM relation (',' relation)*
+      (SELECT setQuantifier? selectItem (',' selectItem)*)?
+      (WHERE where=booleanExpression)?
+      (GROUP BY groupBy)?
+      (HAVING having=booleanExpression)?
+      (WINDOW windowDefinition (',' windowDefinition)*)?
+    ;
+
 groupBy
     : setQuantifier? groupingElement (',' groupingElement)*
     ;
@@ -2010,4 +2020,4 @@ WS
 // when splitting statements with DelimiterLexer
 UNRECOGNIZED
     : .
-    ;
+    ;