fixes #583

Author: wumpz

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

@@ -1269,9 +1269,11 @@ AllTableColumns AllTableColumns():
 
 Alias Alias():
 { String name = null;
+  Token token = null;
   boolean useAs = false; }
 {
-    [<K_AS> { useAs = true; } ] name=RelObjectName()
+    [<K_AS> { useAs = true; } ] 
+	( name=RelObjectName() | token=<S_CHAR_LITERAL> { name=token.image; } )
    { return new Alias(name,useAs); }
 }
 

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

@@ -2750,4 +2750,8 @@ public void testIssue582NumericConstants() throws JSQLParserException {
         assertSqlCanBeParsedAndDeparsed("SELECT x'009fd'");
         assertSqlCanBeParsedAndDeparsed("SELECT X'009fd'");
     }
+    
+    public void testIssue583CharacterLiteralAsAlias() throws JSQLParserException {
+        assertSqlCanBeParsedAndDeparsed("SELECT CASE WHEN T.ISC = 1 THEN T.EXTDESC WHEN T.b = 2 THEN '2' ELSE T.C END AS 'Test' FROM T");
+    }
 }