sql 引擎解析增加 presto try_cast 关键字

src/main/java/com/alibaba/druid/sql/parser/Keywords.java

@@ -52,6 +52,7 @@ public class Keywords {
         map.put("BY", Token.BY);
         map.put("CASE", Token.CASE);
         map.put("CAST", Token.CAST);
+        map.put("TRY_CAST", Token.TRY_CAST);
 
         map.put("CHECK", Token.CHECK);
         map.put("CONSTRAINT", Token.CONSTRAINT);

src/main/java/com/alibaba/druid/sql/parser/SQLExprParser.java

@@ -672,6 +672,7 @@ public class SQLExprParser extends SQLParser {
                 sqlExpr = queryExpr;
                 break;
             case CAST:
+            case TRY_CAST:
                 lexer.nextToken();
                 accept(Token.LPAREN);
                 SQLCastExpr cast = new SQLCastExpr();

src/main/java/com/alibaba/druid/sql/parser/Token.java

@@ -84,6 +84,7 @@ public enum Token {
     ON("ON"), 
     SCHEMA("SCHEMA"), 
     CAST("CAST"),
+    TRY_CAST("TRY_CAST"),
     COLUMN("COLUMN"),
     USE("USE"),
     DATABASE("DATABASE"),