Support underscore separators in numbers for Clickhouse. Fixes #1659 (#1677)

tests/sqlparser_clickhouse.rs

@@ -1649,6 +1649,21 @@ fn parse_table_sample() {
     clickhouse().verified_stmt("SELECT * FROM tbl SAMPLE 1 / 10 OFFSET 1 / 2");
 }
 
+#[test]
+fn parse_numbers_with_underscore() {
+    let canonical = if cfg!(feature = "bigdecimal") {
+        "SELECT 10000"
+    } else {
+        "SELECT 10_000"
+    };
+    let select = clickhouse().verified_only_select_with_canonical("SELECT 10_000", canonical);
+
+    assert_eq!(
+        select.projection,
+        vec![SelectItem::UnnamedExpr(Expr::Value(number("10_000")))]
+    )
+}
+
 fn clickhouse() -> TestedDialects {
     TestedDialects::new(vec![Box::new(ClickHouseDialect {})])
 }