Add support for Recursive CTEs (#278)

i.e. `WITH RECURSIVE ... AS ( ... ) SELECT` - see https://jakewheat.github.io/sql-overview/sql-2016-foundation-grammar.html#with-clause

Fixes #277

tests/sqlparser_common.rs

@@ -2389,7 +2389,7 @@ fn parse_ctes() {
 
     fn assert_ctes_in_select(expected: &[&str], sel: &Query) {
         for (i, exp) in expected.iter().enumerate() {
-            let Cte { alias, query } = &sel.ctes[i];
+            let Cte { alias, query } = &sel.with.as_ref().unwrap().cte_tables[i];
             assert_eq!(*exp, query.to_string());
             assert_eq!(
                 if i == 0 {
@@ -2432,7 +2432,7 @@ fn parse_ctes() {
     // CTE in a CTE...
     let sql = &format!("WITH outer_cte AS ({}) SELECT * FROM outer_cte", with);
     let select = verified_query(sql);
-    assert_ctes_in_select(&cte_sqls, &only(&select.ctes).query);
+    assert_ctes_in_select(&cte_sqls, &only(&select.with.unwrap().cte_tables).query);
 }
 
 #[test]
@@ -2441,10 +2441,47 @@ fn parse_cte_renamed_columns() {
     let query = all_dialects().verified_query(sql);
     assert_eq!(
         vec![Ident::new("col1"), Ident::new("col2")],
-        query.ctes.first().unwrap().alias.columns
+        query
+            .with
+            .unwrap()
+            .cte_tables
+            .first()
+            .unwrap()
+            .alias
+            .columns
     );
 }
 
+#[test]
+fn parse_recursive_cte() {
+    let cte_query = "SELECT 1 UNION ALL SELECT val + 1 FROM nums WHERE val < 10".to_owned();
+    let sql = &format!(
+        "WITH RECURSIVE nums (val) AS ({}) SELECT * FROM nums",
+        cte_query
+    );
+
+    let cte_query = verified_query(&cte_query);
+    let query = verified_query(sql);
+
+    let with = query.with.as_ref().unwrap();
+    assert!(with.recursive);
+    assert_eq!(with.cte_tables.len(), 1);
+    let expected = Cte {
+        alias: TableAlias {
+            name: Ident {
+                value: "nums".to_string(),
+                quote_style: None,
+            },
+            columns: vec![Ident {
+                value: "val".to_string(),
+                quote_style: None,
+            }],
+        },
+        query: cte_query,
+    };
+    assert_eq!(with.cte_tables.first().unwrap(), &expected);
+}
+
 #[test]
 fn parse_derived_tables() {
     let sql = "SELECT a.x, b.y FROM (SELECT x FROM foo) AS a CROSS JOIN (SELECT y FROM bar) AS b";
@@ -3266,8 +3303,8 @@ fn parse_drop_index() {
 fn all_keywords_sorted() {
     // assert!(ALL_KEYWORDS.is_sorted())
     let mut copy = Vec::from(ALL_KEYWORDS);
-    copy.sort();
-    assert!(copy == ALL_KEYWORDS)
+    copy.sort_unstable();
+    assert_eq!(copy, ALL_KEYWORDS)
 }
 
 fn parse_sql_statements(sql: &str) -> Result<Vec<Statement>, ParserError> {