Improved Oracle compatibility for NVL2. Thanks again to litailang for the patch.

h2/src/docsrc/help/help.csv

@@ -3602,6 +3602,7 @@ NULLIF(A, B)
 NVL2(testValue, aValue, bValue)
 ","
 If the test value is null, then 'b' is returned. Otherwise, 'a' is returned.
+The data type of the returned value is the data type of 'a' if this is a text type.
 ","
 NVL2(X, 'not null', 'null')
 "

h2/src/docsrc/html/changelog.html

@@ -18,7 +18,8 @@ Change Log
 <h1>Change Log</h1>
 
 <h2>Next Version (unreleased)</h2>
-<ul><li>CSVREAD now supports the option 'preserveWhitespace'.
+<ul><li>Improved Oracle compatibility for NVL2. Thanks again to litailang for the patch.
+</li><li>CSVREAD now supports the option 'preserveWhitespace'.
 </li><li>Recursive queries with many rows could throw an IndexOutOfBoundsException.
 </li><li>The auto-server mode can't be combined with an in-memory database.
     This invalid combination wasn't detected so far.

h2/src/main/org/h2/expression/Function.java

@@ -1704,8 +1704,23 @@ public class Function extends Expression implements FunctionCall {
             break;
         }
         case CASEWHEN:
+            t = Value.getHigherOrder(args[1].getType(), args[2].getType());
+            p = Math.max(args[1].getPrecision(), args[2].getPrecision());
+            d = Math.max(args[1].getDisplaySize(), args[2].getDisplaySize());
+            s = Math.max(args[1].getScale(), args[2].getScale());
+            break;
         case NVL2:
+            switch (args[1].getType()) {
+            case Value.STRING:
+            case Value.CLOB:
+            case Value.STRING_FIXED:
+            case Value.STRING_IGNORECASE:
+                t = args[1].getType();
+                break;
+            default:
                 t = Value.getHigherOrder(args[1].getType(), args[2].getType());
+                break;
+            }
             p = Math.max(args[1].getPrecision(), args[2].getPrecision());
             d = Math.max(args[1].getDisplaySize(), args[2].getDisplaySize());
             s = Math.max(args[1].getScale(), args[2].getScale());

h2/src/test/org/h2/test/db/TestFunctions.java

@@ -115,6 +115,13 @@ public class TestFunctions extends TestBase implements AggregateFunction {
             assertEquals(ErrorCode.DATA_CONVERSION_ERROR_1, e.getErrorCode());
         }
 
+        // nvl2 should return expr2's datatype, if expr2 is character data.
+        rs = stat.executeQuery("SELECT NVL2(1, 'test', 123), 'test' FROM dual");
+        rs.next();
+        actual = rs.getString(1);
+        assertEquals("test", actual);
+        assertEquals(rs.getMetaData().getColumnType(2), rs.getMetaData().getColumnType(1));
+
         conn.close();
     }