Nested subqueries didn't work for INSERT INTO and IN(..).

h2/src/main/org/h2/command/Parser.java

@@ -862,6 +862,18 @@ public class Parser {
         return prep;
     }
 
+    private boolean isSelect() throws SQLException {
+        int start = lastParseIndex;
+        while (readIf("(")) {
+            // need to read ahead, it could be a nested union:
+            // ((select 1) union (select 1))
+        }
+        boolean select = isToken("SELECT") || isToken("FROM");
+        parseIndex = start;
+        read();
+        return select;
+    }
+
     private Merge parseMerge() throws SQLException {
         Merge command = new Merge(session);
         currentPrepared = command;
@@ -869,7 +881,7 @@ public class Parser {
         Table table = readTableOrView();
         command.setTable(table);
         if (readIf("(")) {
-            if (isToken("SELECT") || isToken("FROM")) {
+            if (isSelect()) {
                 command.setQuery(parseSelect());
                 read(")");
                 return command;
@@ -913,7 +925,7 @@ public class Parser {
             command.setSortedInsertMode(true);
         }
         if (readIf("(")) {
-            if (isToken("SELECT") || isToken("FROM")) {
+            if (isSelect()) {
                 command.setQuery(parseSelect());
                 read(")");
                 return command;
@@ -950,19 +962,8 @@ public class Parser {
         Table table;
         String alias = null;
         if (readIf("(")) {
-            // need to read ahead, it could be a nested union or join:
-            // select 1 from (((select 1) union (select 1)) union (select 1));
-            // select * from ((test d1 inner join test d2 on d1.id = d2.id)
-            // inner join test d3 on d1.id = d3.id) inner join test d4
-            // on d4.id = d1.id;
+            if (isSelect()) {
                 int start = lastParseIndex;
-            while (readIf("(")) {
-                // ignore, but go back later
-            }
-            if (isToken("SELECT") || isToken("FROM")) {
-                parseIndex = start;
-                read();
-                start = lastParseIndex;
                 int paramIndex = parameters.size();
                 Query query = parseSelectUnion();
                 read(")");
@@ -982,8 +983,6 @@ public class Parser {
                 alias = session.getNextSystemIdentifier(sqlCommand);
                 table = TableView.createTempView(s, session.getUser(), alias, query, currentSelect);
             } else {
-                parseIndex = start;
-                read();
                 TableFilter top = readTableFilter(fromOuter);
                 top = readJoin(top, currentSelect, fromOuter);
                 read(")");
@@ -1755,7 +1754,7 @@ public class Parser {
                 if (readIf(")")) {
                     r = ValueExpression.get(ValueBoolean.get(false));
                 } else {
-                    if (isToken("SELECT") || isToken("FROM")) {
+                    if (isSelect()) {
                         Query query = parseSelect();
                         r = new ConditionInSelect(database, r, query, false, Comparison.EQUAL);
                     } else {