fixes #862

Author: wumpz

README.md

@@ -65,6 +65,7 @@ Also I would like to know about needed examples or documentation stuff.
 
 ## Extensions in the latest SNAPSHOT version 3.1
 
+* allow more complex expressions for **CASE**.
 * allowed **start** as object name as column name or table name
 * introduced more positions for **!** instead of **NOT**
 * allowed more complex expressions within **if** function

src/main/jjtree/net/sf/jsqlparser/parser/JSqlParserCC.jjt

@@ -3234,7 +3234,7 @@ Expression CaseWhenExpression() #CaseWhenExpression:
     (
             ( clause=WhenThenSearchCondition() { whenClauses.add(clause); } )+
         |
-            (LOOKAHEAD(RegularCondition()) switchExp=RegularCondition() | switchExp=BitwiseAndOr())
+            switchExp=Condition()
              ( clause=WhenThenValue() { whenClauses.add(clause); } )+
     )
    [<K_ELSE> elseExp=Condition()]

src/test/java/net/sf/jsqlparser/statement/select/SelectTest.java

@@ -1297,6 +1297,11 @@ public void testIssue235SimplifiedCase3() throws JSQLParserException {
     public void testIssue235SimplifiedCase4() throws JSQLParserException {
         assertSqlCanBeParsedAndDeparsed("SELECT CASE WHEN (CASE WHEN (CASE WHEN (CASE WHEN (1) THEN 0 END) THEN 0 END) THEN 0 END) THEN 0 END FROM a");
     }
+    
+    @Test
+    public void testIssue862CaseWhenConcat() throws JSQLParserException {
+        assertSqlCanBeParsedAndDeparsed("SELECT c1, CASE c1 || c2 WHEN '091' THEN '2' ELSE '1' END AS c11 FROM T2");
+    }
 
     @Test
     public void testReplaceAsFunction() throws JSQLParserException {