fix: backticks in count_distinct

prql-compiler/src/sql/std_impl.prql

@@ -7,7 +7,7 @@ func average <scalar|column> column ->  s"AVG({column})"
 func count <scalar|column> non_null:s"*" ->  s"COUNT({non_null})"
 # TODO: Possibly make this into `count distinct:true` (or like `distinct:` as an
 # abbreviation of that?)
-func count_distinct <scalar|column> column ->  s"COUNT(DISTINCT `{column}`)"
+func count_distinct <scalar|column> column ->  s"COUNT(DISTINCT {column})"
 
 # Window functions
 func lag<column> offset column ->  s"LAG({column}, {offset})"

prql-compiler/src/test.rs

@@ -1711,22 +1711,39 @@ fn test_sql_of_ast_2() {
 
 #[test]
 fn test_prql_to_sql_1() {
-    let query = r#"
+    assert_display_snapshot!(compile(r#"
     from employees
     aggregate [
         count non_null:salary,
         sum salary,
     ]
-    "#;
-    let sql = compile(query).unwrap();
-    assert_display_snapshot!(sql,
+    "#).unwrap(),
         @r###"
     SELECT
       COUNT(salary),
       SUM(salary)
     FROM
       employees
     "###
+    );
+    assert_display_snapshot!(compile(r#"
+    prql target:sql.postgres
+    from developers
+    group team (
+        aggregate [
+            skill_width = count_distinct specialty,
+        ]
+    )
+    "#).unwrap(),
+        @r###"
+    SELECT
+      team,
+      COUNT(DISTINCT specialty) AS skill_width
+    FROM
+      developers
+    GROUP BY
+      team
+    "###
     )
 }