diff --git a/lexer/lexer.mll b/lexer/lexer.mll
index 946bf27..f735e09 100644
--- a/lexer/lexer.mll
+++ b/lexer/lexer.mll
@@ -8,44 +8,48 @@ let alpha = ['a'-'z' 'A'-'Z' '_']
 let alphanumeric = (alpha|digit)
 
 rule read_token = parse
-  | "SELECT"    { SELECT }
-  | "AVG"       { AVG }
-  | "MAX"       { MAX }
-  | "MIN"       { MIN }
-  | "SUM"       { SUM }
-  | "COUNT"     { COUNT }
-  | "DISTINCT"  { DISTINCT }
-  | "FROM"      { FROM }
-  | "INNER"     { INNER }
-  | "LEFT"      { LEFT }
-  | "RIGHT"     { RIGHT }
-  | "CROSS"     { CROSS }
-  | "UNION"     { UNION }
-  | "NATURAL"   { NATURAL }
-  | "JOIN"      { JOIN }
-  | "ON"        { ON }
-  | "OR"        { OR }
-  | "AND"       { AND }
-  | "WHERE"     { WHERE }
-  | "HAVING"    { HAVING }
-  | "BETWEEN"   { BETWEEN }
-  | "IN"        { IN }
-  | "LIKE"      { LIKE }
-  | "GROUP"     { GROUP }
-  | "BY"        { BY }
-  | "*"         { ASTERISK }
-  | "."         { DOT }
-  | "="         { EQUALS_OPERATOR }
-  | "("         { LEFT_PAREN }
-  | ")"         { RIGHT_PAREN }
-  | ","         { COMMA }
-  | "|"         { PIPE }
-  | "'"         { QUOTE }
-  | "+"         { PLUS_SIGN }
-  | "-"         { MINUS_SIGN }
-  | whitespace  { read_token lexbuf }
-  | digit+      { INTEGER }
-  | digit+"."digit+ { FLOAT }
-  | '.'digit+   { FLOAT }
-  | alpha alphanumeric* as ident      { IDENT ident }
-  | eof         { EOF }
+  | "SELECT"                      { SELECT }
+  | "AS"                          { AS }
+  | "DATE"                        { DATE }
+  | "TIME"                        { TIME }
+  | "AVG"                         { AVG }
+  | "MAX"                         { MAX }
+  | "MIN"                         { MIN }
+  | "SUM"                         { SUM }
+  | "COUNT"                       { COUNT }
+  | "DISTINCT"                    { DISTINCT }
+  | "FROM"                        { FROM }
+  | "INNER"                       { INNER }
+  | "LEFT"                        { LEFT }
+  | "RIGHT"                       { RIGHT }
+  | "CROSS"                       { CROSS }
+  | "UNION"                       { UNION }
+  | "NATURAL"                     { NATURAL }
+  | "JOIN"                        { JOIN }
+  | "ON"                          { ON }
+  | "OR"                          { OR }
+  | "AND"                         { AND }
+  | "WHERE"                       { WHERE }
+  | "HAVING"                      { HAVING }
+  | "BETWEEN"                     { BETWEEN }
+  | "IN"                          { IN }
+  | "LIKE"                        { LIKE }
+  | "GROUP"                       { GROUP }
+  | "BY"                          { BY }
+  | "*"                           { ASTERISK }
+  | "."                           { DOT }
+  | "="                           { EQUALS_OPERATOR }
+  | "("                           { LEFT_PAREN }
+  | ")"                           { RIGHT_PAREN }
+  | ','                           { COMMA }
+  | "|"                           { PIPE }
+  | "'"                           { QUOTE }
+  | "+"                           { PLUS_SIGN }
+  | "-"                           { MINUS_SIGN }
+  | ':'                           { COLON }
+  | whitespace                    { read_token lexbuf }
+  | digit+ as integer             { INTEGER (int_of_string integer) }
+  | digit+"."digit+               { FLOAT }
+  | '.'digit+                     { FLOAT }
+  | alpha alphanumeric* as ident  { IDENT ident }
+  | eof                           { EOF }