Implement DB2 Special Register Date Time CURRENT DATE and CURRENT TIME (#1252)

* Implement DB2 Special Register Date Time CURRENT DATE and CURRENT TIME
Fixes issue #1249
(Although there are more Special Registers which are not supported yet.)

* Make the spaces mandatory
Add 2 more tests

Author: manticore-projects

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

@@ -347,7 +347,11 @@ TOKEN: /* SQL Keywords. prefixed with K_ to avoid name clashes */
 |   <K_THEN:"THEN">
 |   <K_TEMP:"TEMP">
 |   <K_TEMPORARY:"TEMPORARY">
-|   <K_TIME_KEY_EXPR : ( "CURRENT_TIMESTAMP" | "CURRENT_TIME" | "CURRENT_DATE" ) ( "()" )?>
+|   <K_TIME_KEY_EXPR : ( 
+                         ("CURRENT" ( "_" | (" ")+ ) "TIMESTAMP") 
+                         | ("CURRENT" ( "_" | (" ")+ ) "TIME")
+                         | ("CURRENT" ( "_" | (" ")+ ) "DATE")
+                       ) ( "()" )?>
 |   <K_TIMEOUT:"TIMEOUT">
 |   <K_TO:"TO">
 |   <K_TOP:"TOP">

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

@@ -4649,4 +4649,14 @@ public void testSelectAllOperatorIssue1140() throws JSQLParserException {
     public void testSelectAllOperatorIssue1140_2() throws JSQLParserException {
         assertSqlCanBeParsedAndDeparsed("SELECT * FROM table t0 WHERE t0.id != all(?::uuid[])");
     }
+    
+    @Test
+    public void testDB2SpecialRegisterDateTimeIssue1249() throws JSQLParserException {
+        assertSqlCanBeParsedAndDeparsed("SELECT * FROM test.abc WHERE col > CURRENT_TIME", true);
+        assertSqlCanBeParsedAndDeparsed("SELECT * FROM test.abc WHERE col > CURRENT TIME", true);
+        assertSqlCanBeParsedAndDeparsed("SELECT * FROM test.abc WHERE col > CURRENT_TIMESTAMP", true);
+        assertSqlCanBeParsedAndDeparsed("SELECT * FROM test.abc WHERE col > CURRENT TIMESTAMP", true);
+        assertSqlCanBeParsedAndDeparsed("SELECT * FROM test.abc WHERE col > CURRENT_DATE", true);
+        assertSqlCanBeParsedAndDeparsed("SELECT * FROM test.abc WHERE col > CURRENT DATE", true);
+    }
 }